The Routledge International Handbook of Human Aggression: Current Issues and Perspectives 9781138668188, 9781315618777

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The Routledge International Handbook of Human Aggression

Drawing upon international expertise, and including some of the most well-known academics and practitioners in the field, The Routledge International Handbook of Human Aggression is the first reference work to fully capture how our understanding of aggression has been refined and reconceptualised in recent years. Divided into five sections, the handbook covers some of the most interesting and timely topics within human aggression research, with analysis of both indirect and direct forms of aggression, and including chapters on sexual aggression, workplace bullying, animal abuse, gang violence and female aggression. It recognises that, in many cases, aggression is an adaptive choice rather than a moral choice. Providing practitioners and academics with an up-to-date resource that covers broad areas of interest and application, the book will be essential reading for students, researchers and practitioners associated with a range of social science disciplines, including psychology, criminology, social work and sociology, particularly those with an interest in developmental, organisational, forensic and criminal justice allied disciplines. Jane L. Ireland is a Forensic Psychologist, Chartered Psychologist and Chartered Scientist. Professor Ireland holds a professorial chair at the University of Central Lancashire and is Violence Treatment Lead within High Secure Services, Ashworth Hospital, Mersey Care NHS Trust. She is elected academy fellow of the Council of the Academy of Social Sciences and fellow of the International Society for Research on Aggression (ISRA). She holds three further (visiting/ honorary) professorships at Åbo Akademi University in Finland, Charles Sturt University, Australia and Cardiff Metropolitan University. She has over 150 publications in forensic psychology, the majority of which fall within the area of aggression. Philip Birch, BSocSci.(Hons); PG Cert (HEP); PG Cert. (SSRM); PG Dip (SocSci); MSc; PhD

is a Senior Lecturer in Criminology in the Centre for Law and Justice at Charles Sturt University, Australia. He has previously held posts at the University of Western Sydney, the University of New South Wales, Sydney, Australia and the University of Huddersfield, in the UK. Prior to entering academia, Philip worked as a criminologist in the field, holding posts in the UK prison service as well as in the crime and disorder field, which involved managing a specialist crime

unit. Philip has published internationally, including books, book chapters, peer-reviewed articles and government reports in his main areas of research – offender management and rehabilitation; police, prisons and probation practices; gender symmetry violence with a particular focus on domestic family violence and sex work. He has secured over $790,000 in research grants, which have addressed a variety of themes within his areas of expertise. Philip holds an honorary research fellowship at the Institute of Positive Psychology and Education, Australia Catholic University and in the School of Psychology, University of Central Lancashire, UK, as well as being a Senior Research Associate in the Ashworth Research Centre, Mersey Health Care, National Health Services, UK. Philip is the Editor-in-Chief of the Journal of Criminological Research, Policy and Practice and currently sits on the editorial board of the Journal of Aggression, Conflict and Peace Research. Carol A. Ireland, PhD, is a Chartered Psychologist, Consultant Forensic Psychologist and Chartered Scientist. She works for Coastal Child and Adult Therapeutic Services – CCATS (www.ccats.org.uk), which is a community-based child and adult therapeutic service in the UK, and where she is the Sex Offender Lead, further leading on matters linked to sexual exploitation. She also works at the University of Central Lancashire, where she is the Director of Studies for the MSc in Forensic Psychology, as well as the Senior Research Lead at the Ashworth Research Centre, Ashworth Hospital, Mersey Care NHS Trust.

The Routledge International Handbook of Human Aggression Current Issues and Perspectives

Edited by Jane L. Ireland, Philip Birch and Carol A. Ireland

First published 2018 by Routledge 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN and by Routledge 711 Third Avenue, New York, NY 10017 Routledge is an imprint of the Taylor & Francis Group, an informa business © 2018 selection and editorial matter, Jane L. Ireland, Philip Birch and Carol A. Ireland; individual chapters, the contributors The right of Jane L. Ireland, Philip Birch and Carol A. Ireland to be identified as the authors of the editorial material, and of the authors for their individual chapters, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book has been requested ISBN: 978-1-138-66818-8 (hbk) ISBN: 978-1-315-61877-7 (ebk) Typeset in Bembo by Keystroke, Neville Lodge, Tettenhall, Wolverhampton

Dedications

To my twin sister Jane, who always stands by and supports me: I love her with all my heart. (CI) To Jonathan, Sebastian and Leo, the most peaceful people I know, and to Mojo, Miss Sparkles and Elfrid, the most peaceful four-legged people I know. (JI) To Irena Veljanova for her support and friendship. (PB)

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Contents

List of figures List of tables List of contributors

xi xiii xv

Preface: Human aggression: How far have we come? Jane L. Ireland, Philip Birch, Carol A. Ireland

xxv

SECTION I

Understanding general aggression 1 The development of aggression in childhood and adolescence: A focus on relationships Debra J. Pepler

1 3

2 Sex differences in aggression Kaj Björkqvist, Karin Österman

19

3 Hegemonic masculinity and aggression Ruschelle M. Leone, Dominic J. Parrott

31

4 The biology of human aggression Tracy A. Bedrosian, Randy J. Nelson

43

5 Aggression motivation and inhibition: Theoretical underpinnings and a new model Ioan Ohlsson

54

6 Homicide adaptations Joshua Duntley, David M. Buss

70

7 Human aggression from a cross-cultural perspective Douglas P. Fry

83

8 Treatment intervention for aggression: Promoting individual change Jane L. Ireland, Syeda Batool

94 vii

Contents

SECTION II

Bullying across contexts 9 Integrating multi-disciplinary social science theories and perspectives to understand school bullying and victimisation Jun Sung Hong, Dorothy L. Espelage, Simon C. Hunter, Paula Allen-Meares

107

109

10 Aggression in the workplace Al-Karim Samnani

121

11 Cyberbullying Robin Kowalski

131

12 Alterophobic bullying and violence Stephen James Minton

143

SECTION III

Relationships and family aggression

153

13 Violence to partners: Gender symmetry revisited John Archer

155

14 Stalking and harassment David V. James, Rachel D. MacKenzie

170

15 Animal maltreatment in households experiencing family violence Shelby Elaine McDonald

183

16 Treating stalking behaviour: A framework for understanding process components Philip Birch, Jane L. Ireland, Nikola Ninaus

194

17 Using the research evidence to inform the assessment and treatment of intimate partner aggression Louise Dixon, Devon L. L. Polaschek

205

18 Attitudes towards ‘honor’ violence and killings in collectivist cultures: Gender differences in Middle Eastern, North African, South Asian (MENASA) and Turkish populations Roxanne Khan 19 Towards evidence-based treatment of partner violence in LGBT relationships Erica Bowen viii

216

227

Contents

20 Raising awareness, improving victim safety: Exploring the efficacy of proactive domestic and family violence prevention measures Philip Birch, Irena Colakova Veljanova

238

SECTION IV

Sexual aggression

249

21 The development of sexual aggression: A tripartite model and a life span perspective Howard E. Barbaree, Lynn O. Lightfoot, Robert A. Prentky

251

22 Examining harmful sexual behaviour in male children: Considering the implications for practice Carol A. Ireland

267

23 Females who sexually offend: Theory, research, and treatment Emily Blake,Theresa A. Gannon

278

24 Assessment of sexual violence Jan Looman, Jeffrey Abracen

291

25 Thinking outside of the box: Advancements in theory, practice and evaluation in sexual offending interventions Kerensa Hocken, Neil Gredecki

302

SECTION V

Contemporary and emerging issues

317

26 The impact of violent media on aggression Barbara Krahé

319

27 Homophobic and non-homophobic aggression: Examining its portrayal in print media Philip Birch, Rebecca Ozanne, Jane L. Ireland

331

28 Narrowing the scope of psychopathy in explanations of offending: Towards an understanding of persistent violence Evan C. McCuish, Raymond R. Corrado, Jennifer Yang

342

29 Victims of violent crime: The emerging field of victimology Benjamin Roebuck, Lynn A. Stewart 30 Psychosocial determinants of violence and trauma-informed implications for treatment Deborah Horowitz, Margaret Guyer, Kathy Sanders

353

364

ix

Contents

31 Jihadi-Salafi terrorism and violent extremism in the era of al-Qaeda and the Islamic State Greg Barton

376

32 Drive-bys in Chiraq or ethnic genocide in Iraq: Can violent street gangs inform our comprehension of the Islamic State? Matthew Valasik, Matthew D. Phillips

388

33 Gang violence and social media Keir Irwin-Rogers, James Densley, Craig Pinkney

400

34 Group process and gang delinquency intervention: Gang activity regulation and the group nature of gang violence Matthew Valasik, Shannon E. Reid, Jenny S.West, Jason Gravel

411

Index

424

x

Figures

2.1

5.1 6.1

13.1 13.2 13.3 16.1 21.1 21.2 21.3 21.4 26.1

26.2

Proportions of victimisation from physical, verbal, and indirect aggression. Peer-estimated data of girls and boys of three age groups from Finland, Israel, Italy, and Poland, obtained with the Direct & Indirect Aggression Scales Applied Integrated Model of Aggression Motivation (AIM-AM) Homicide leads to a decline in victims’ fitness, which selects for anti-homicide defences, which lead to a decline in killers’ fitness, which selects for new or refined homicide adaptations, ad infinitum Sex differences in partner violence according to measures Sex differences in community studies from non-Western and Western nations Examples of GEM values Stalkers Intervention Process (SIP): Applying components from the Integrated Model and accounting for reinforcement Causal paths for the origin of sexual aggression From the FBI Uniform Crime Report. Plots the mean yearly arrest rate of nine years plotted over the age of the person arrested Mean Free T Index plotted over the mean age of six age cohorts Mean of the three largest responses (CCs) during assessment session plotted over the age of the individual being tested Effect sizes (weighted by sample size) from experimental, longitudinal, and cross-sectional “best-practice” studies for the link between violent video game play and aggression-related outcomes Effects of long-term exposure to media violence according to the General Aggression Model

21 64

76 162 163 164 200 259 260 261 261

322 326

xi

Tables

2.1

5.1 19.1 22.1 22.2 25.1 26.1 27.1

Bivariate and partial correlations (controlling for empathy) between peer-estimated social intelligence and different types of peer-estimated conflict behaviour Summary of studies exploring underlying motivations for aggression The four parallel phases of individual sexual and group membership identity development Examples of developmental factors relating to general delinquency Two main groups of offenders The Maryland Scientific Method Scale (MSMS) Processes underlying the effects of exposure to media violence on aggression Linguistic inquiry and word count text analysis of homophobic aggression and non-homophobic aggression in print media reports

24 56 235 269 270 311 323 339

xiii

Contributors

Jeffrey Abracen has worked with the Correctional Service of Canada (CSC) from 1995 and has

occupied a number of positions within the organisation. Dr Abracen is currently the Chief Psychologist for Central District (Ontario) Parole. He has previously been responsible for the management of sex offender treatment programmes in Central District (Ontario) Parole and has worked at the High Intensity Sex Offender Treatment programme operated by CSC at the Regional Treatment Centre (Ontario). Paula Allen-Meares, PhD, MSW, is the John Corbally Presidential Professor and Professor of Medicine in the College of Medicine at the University of Illinois at Chicago (UIC). She is Chancellor Emerita at UIC and Vice President of the University of Illinois. She also holds faculty appointments on both the UIC and University of Illinois at Urbana-Champaign. Dr Allen-Meares is Dean and Professor Emerita and the Normal Radin Collegiate Professor at the University of Michigan. She is an elected member of the National Academy of Medicine, the Royal Society of Medicine and is a past trustee of the New York Academy of Medicine. She serves on a number of editorial boards and has over 170 articles, chapters, books and commentaries. Her scholarly works have been translated into other languages and studied around the world. John Archer is Professor of Psychology at the University of Central Lancashire, United Kingdom.

He is the author of over 100 articles, mostly on human aggression. He is the author of several books including: The Behavioural Biology of Aggression, The Nature of Grief and (with Barbara Lloyd) Sex and Gender. He is a former president of the International Society for Research on Aggression (ISRA), a fellow of the British Psychological Society and Editor-in-Chief of Aggressive Behavior (2012–present). He was recipient of the International Society for Research on Aggression’s Scott Award, for lifetime achievement, in 2016. Howard E. Barbaree is a psychologist and Professor of Psychiatry at the University of Toronto and Vice-President of Research and Academics at Waypoint Centre for Mental Health Care. He received the 2001 Significant Achievement Award from the Association for the Treatment of Sexual Abusers and the 2011 Don Andrews Career Contribution Award from the Canadian Psychological Association. He was Editor-in-Chief of Sexual Abuse: A Journal of Research and Treatment from 2004 to 2010. Greg Barton is Co-Director of the Australian Intervention Support Hub (AISH) and Professor

of Global Islamic Politics at the Alfred Deakin Institute. Greg has been active for the past 20 years in interfaith dialogue initiatives and has a deep commitment to building understanding xv

Contributors

of Islam and Muslim society. The central axis of his research interests is the way in which religious thought, individual believers and religious communities respond to modernity and to the modern nation state. He also has a strong general interest in comparative international politics. He has undertaken extensive research on Indonesian politics and society, especially of the role of Islam. Since 2004 he has made a comparative study of progressive Islamic thought in Turkey and Indonesia. He also has a general interest in security studies and human security and a particular interest in countering violent extremism, and continues to research Islamic and Islamist movements in Southeast Asia and around the world. Syeda Batool has recently completed her bachelor’s degree in Psychology and a master’s degree in Health Psychology. She has an avid interest in the study of mental health, consciences and morality and hopes to pursue a career in this area. She is currently completing her research internship in a forensic psychiatric unit and on placement, assessing impacts of health promotion on children. Tracy A. Bedrosian is a post-doctoral fellow in the Laboratory of Genetics at the Salk Institute for Biological Studies. Dr Bedrosian earned her BS in Neuroscience from the University of Michigan, Ann Arbor. She went on to earn her PhD in Neuroscience from The Ohio State University before beginning post-doctoral work at the Salk Institute. Dr Bedrosian has published extensively in the field of behavioural neuroscience, including several articles and chapters on the neurobiology of aggression. Kaj Björkqvist has been Professor of Developmental Psychology at Åbo Akademi University, Finland, since 1992. He is a former president of the International Society of Research on Aggression. His research is focused on different forms of human aggression, in particular, indirect aggression, sex differences in aggression, school and workplace bullying, conflict resolution, media violence and cross-cultural comparisons. Emily Blake, PhD, is an independent researcher who works regularly with the University of

Kent. Emily has conducted and assisted with research in the field of adult and child sexual offending, and is particularly interested in the aetiology of sexual offending behaviour, risk of offending and associated mental health and treatment needs. More recently, Emily has been involved in ongoing research in the field of adults and young people with an intellectual disability or autism who have sexually offended or display sexually harmful behaviour. Erica Bowen is Professor of Violence Prevention Research within the National Centre for the Study and Prevention of Violence and Abuse at the University of Worcester. Erica has researched domestic violence with a focus on evaluating and designing prevention programmes for adults and young people since 2000. She is a Chartered Psychologist (British Psychological Society) and registered forensic psychologist (Health and Care Professions Council). Her current research interests include understanding the factors that lead to resilience in children exposed to inter-parental violence, and how best to address the needs of perpetrators of domestic violence who have learning disabilities. David M. Buss is Professor of Psychology, University of Texas, Austin. He previously taught at Harvard and the University of Michigan. His most recent book is The Evolution of Desire: Strategies of Human Mating. His other books include Evolutionary Psychology: The New Science of the Mind; xvi

Contributors

The Dangerous Passion: Why Jealousy is as Necessary as Love and Sex; The Murderer Next Door: Why the Mind is Designed to Kill; and Why Women Have Sex (with Cindy Meston). Buss has roughly 300 scientific publications, and he has been cited as one of the 30 most influential living psychologists. Raymond R. Corrado is a Full Professor in the School of Criminology at Simon Fraser University

and was an associate faculty member in the Psychology department and the Faculty of Health Sciences. He is a Visiting Fellow at Clare Hall College and the Institute of Criminology, University of Cambridge. He is a founding member of the Mental Health, Law, and Policy Institute at Simon Fraser University. He has published over 100 articles and book chapters on a wide variety of policy issues, including juvenile justice, violent young offenders, mental health, adolescent psychopathy, Aboriginal victimisation, child/adolescent case management strategies and terrorism. James Densley is an Associate Professor of Criminal Justice at Metropolitan State University (USA), part of the Minnesota State system, and an Associate of the Extra-Legal Governance Institute at the University of Oxford (UK). He has received local, national and international media attention for his work on street gangs, criminal networks, violence and policing. Dr Densley is the author of How Gangs Work: An Ethnography of Youth Violence and over 20 refereed articles and book chapters in leading social science outlets. He earned his doctorate in sociology from the University of Oxford. Louise Dixon, PhD, CPsychol is a Reader in Forensic Psychology at Victoria University of

Wellington and a UK-registered forensic psychologist. She specialises in the prevention of interpersonal aggression and violence. Primarily, her research has centred on the study of intimate partner violence and abuse, and the overlap with child maltreatment in the family. Dr Dixon has received funding from prestigious UK research councils such as the Economic and Social Research Council, Higher Education Funding Council for England and Police Knowledge fund. She is a series editor to the What Works in Offender Rehabilitation book series for Wiley-Blackwell. Joshua Duntley, PhD, is an Associate Professor of Criminal Justice and Associated Faculty in the

Psychology Program at Stockton University. His research and publications examine homicide, non-lethal violence, stalking, victimisation and human mating strategies. He co-edited the volume Evolutionary Forensic Psychology and is co-author of the book Research Stories for Introductory Psychology. Joshua is also the Director of Stockton University’s Honors Program and Co-Director of the Stockton CSI summer camp for high school students. Dorothy L. Espelage, PhD, is Professor of Psychology at the University of Florida. She is

the recipient of the APA Lifetime Achievement Award in Prevention Science and the 2016 APA Award for Distinguished Contributions to Research in Public Policy, and is a fellow of APS, APA and AERA. She earned her PhD in Counseling Psychology from Indiana University in 1997. Over the last 20 years, she has authored over 140 peer-reviewed articles, five edited books and 30 chapters on bullying, homophobic teasing, sexual harassment, dating violence and gang violence. Her research focuses on translating empirical findings into prevention and intervention programming and she has secured six and half million dollars of external funding. xvii

Contributors

Douglas P. Fry is Professor and Chair of the Anthropology Department at the University of Alabama at Birmingham and concurrently Docent in the Developmental Psychology Program at Åbo Akademi University in Finland. Professor Fry earned his doctorate in Anthropology from Indiana University in 1986. Fry has written extensively on aggression, conflict resolution and war and peace. He is author of Beyond War: The Human Potential for Peace and co-editor of Keeping the Peace: Conflict Resolution and Peaceful Societies Around the World and Cultural Variation in Conflict Resolution: Alternatives to Violence. He is an associate editor of the Encyclopedia of Violence, Peace, and Conflict. Dr Fry’s own cross-cultural research showing a paucity of war among nomadic forager societies has been published in Science. He is the recipient of the 2015 Peace Scholar-Educator Award, of the Peace and Justice Studies Association. Theresa A. Gannon, DPhil, CPsychol (Forensic) is Professor of Forensic Psychology and

Director of CORE-FP at the University of Kent, UK. Theresa also works as a practitioner consultant forensic psychologist for Kent and Medway NHS and Social Care Partnership Trust, UK. Theresa has published over 100 chapters, articles, books and other scholarly works in the areas of male- and female-perpetrated sexual offending. She is particularly interested in research relating to both the treatment needs and overall supervision of sexual offenders. Theresa is editor of Psychology Crime and Law and associate editor of Sexual Abuse: A Journal of Research and Treatment. Jason Gravel is a PhD candidate in the Department of Criminology, Law, and Society at the University of California, Irvine. He completed his master’s thesis on criminal versatility in street gang networks at Simon Fraser University in 2013. His research interests include social network analysis, street gangs, co-offending, gun violence and crime prevention and intervention. His recent work has been published in Criminology & Public Policy, Journal of Quantitative Criminology, Injury Prevention and Criminal Justice & Behavior. Neil Gredecki, PhD, is a registered forensic psychologist with over 14 years’ experience of working in prisons and a variety of NHS and private sector settings. This includes high, medium and low secure psychiatric hospitals as well as working with adolescents and in community and inpatient settings. He holds the role of Registrar and Chief Supervisor for the British Psychological Society’s Qualification in Forensic Psychology and currently has a senior role within Her Majesty’s Prison & Probation Service (HMPPS). In addition to working in clinical posts, Neil has extensive experience of supervision and management and conducts research with staff working in forensic settings. He is co-editor of the Journal of Forensic Practice. Margaret Guyer, PhD, a clinician and researcher, has worked with people with severe mental illness for more than 20 years. As an administrator with the Massachusetts Department of Mental Health she is responsible for the identification, evaluation and dissemination of evidence-based practices within the Department of Mental Health and among community providers. She serves as the Chair for the Massachusetts Department of Mental Health Institutional Review Board, manages the Department’s Training Grants and Research Centers of Excellence as well as serving as the liaison with the Department of Public Health concerning suicide. Kerensa Hocken, PhD, is a registered forensic psychologist and British Psychological Society Chartered Psychologist. She has worked with people convicted of sexual offences for 17 years and specialises in working with those who have intellectual disabilities. Kerensa is currently the Midlands Lead Psychologist for people convicted of sexual offences in Her Majesty’s Prison & xviii

Contributors

Probation Service (HMPPS) where she has been involved in the development of HMPPS treatment programmes for sexual offending. Kerensa is a trustee and co-founder of the Safer Living Foundation (SLF), a charity which sets out to prevent sexual abuse by working with those who have offended or are at risk of committing a sexual offence. Jun Sung Hong, PhD, is an Assistant Professor in the School of Social Work at Wayne State University and an Adjunct Assistant Professor in the Department of Social Welfare at Sungkyunkwan University in Seoul, South Korea. He is a recipient of the Academy of Scholars Junior Faculty Award at Wayne State University (2017–2018) and the Alberti Center Early Career Award at the Alberti Center for Bullying Abuse Prevention (2017–2018). He has authored numerous peer reviewed articles and book chapters. He is currently on the editorial boards for the Journal of Family Violence, the Journal of Child and Family Studies, the Journal of Youth and Adolescence and Psychology of Violence. He is currently a guest editor for the American Journal of Orthopsychiatry and the Journal of Child and Family Studies. He holds an MSW and a PhD in Social Work from the University of Michigan and the University of Illinois at UrbanaChampaign, respectively. Deborah Horowitz, MSW, is a licensed independent clinical social worker with more than

20 years of experience as a clinician, researcher and educator in the health care field. Currently a clinical training specialist with the Massachusetts Department of Mental Health, she is the lead author of Safety, Hope, and Healing (SHH); a curriculum designed to facilitate culture change around the concepts of trauma, violence and recovery. Ms Horowitz is also the statewide chair of the First Aid Support Team (FAST) a staff-to-staff tertiary response to workplace trauma and the companion programme to SHH. Simon C. Hunter, PhD, works at the University of Strathclyde in Glasgow where he is a Senior

Lecturer in the School of Psychological Sciences and Health, and he is also a Centre for Health Policy Fellow in the International Public Policy Institute. He is also an Honorary Research Fellow in the Faculty of Education at the University of Western Australia. Simon earned his PhD at the University of Strathclyde in 2004, and has since published over 40 peer-reviewed articles on topics including bullying, atypical development and health. He is also an associate editor at the British Journal of Developmental Psychology. Keir Irwin-Rogers is a lecturer in Criminology with The Open University. He has conducted a range of research on gangs and youth violence and presented his most recent project on gang violence and online social media activity to the UK Home Office, the National Police Chiefs’ Council and the Youth Justice Board Gangs Forum. Irwin-Rogers has published on a number of criminal justice-related subjects, including gangs and youth violence, sentencing, community sanctions and deterrence. He completed a PhD in Criminal Justice at the University of Sheffield and is currently studying for a BSc in Mathematics and Statistics. David V. James is a consultant forensic psychiatrist and was formerly a Senior Lecturer in

Forensic Psychiatry at University College London (UCL). He was co-founder of the Fixated Threat Assessment Centre (FTAC), a novel joint police/National Health Service unit for the assessment and management of concerning and threatening behaviour towards politicians and the Royal Family. He was co-founder of the UK’s National Stalking Clinic. He is author or co-author of 60 papers in the specialist literature and 15 book chapters. He is a co-author of the Stalking Risk Profile and of the Communications Threat Assessment Protocol. He is currently a director xix

Contributors

of Theseus LLP, a company which provides an FTAC-style threat management service to private individuals and institutions. Roxanne Khan, PhD, is a Senior Lecturer in Forensic Psychology at the University of Central Lancashire. She is also a Chartered Psychologist and Chartered Scientist, with experience of working with perpetrators and victims of violence in secure and community settings. Primarily an aggression researcher, Dr Khan maintains a long-standing research interest in family and community violence, and this is reflected in her publication profile. She has authored work that examines intimate partner violence, child and adult sexual abuse, including sexual coercion and exploitation. Her research interest extends to sibling victimisation and the psychology of ‘honour’-based violence. Robin Kowalski is a Trevillian Professor of Psychology at Clemson University. She obtained her PhD in Social Psychology from the University of North Carolina at Greensboro. Her research interests focus on aversive interpersonal behaviours, most notably complaining and cyberbullying. She is the author or co-author of several books including Complaining, Teasing, and Other Annoying Behaviors, Aversive Interpersonal Behaviors and Cyber Bullying: Bullying in the Digital Age. Dr Kowalski has received several awards including Clemson’s Award of Distinction, Clemson’s College of Business and Behavioral Science Award for Excellence in Undergraduate Teaching, the Phil Prince Award for Excellence and Innovation in the Classroom and Clemson’s College of Business and Behavioral Science Senior Research Award. She was a finalist for the 2013 and 2014 South Carolina Governor’s Professor of the Year Awards. Barbara Krahé is Professor of Social Psychology at the University of Potsdam, Germany. Her

research interests lie in the area of applied social psychology, in particular aggression research (media violence, sexual aggression) and social cognition research applied to legal decisionmaking. She is President-Elect of the International Society for Research on Aggression (ISRA) and author of the textbook, The Social Psychology of Aggression. She is a fellow of the British Psychological Society and the Association for Psychological Science and a member of the Berlin-Brandenburg Academy of Sciences. Ruschelle M. Leone is a doctoral student in Clinical Psychology at Georgia State University. She is interested in identifying risk and protective factors to reduce alcohol-related aggression, with a particular focus on bystander intervention. Much of her work has focused on dispositional (e.g., adherence to traditional masculinity) and situational (e.g., peer norms) factors that interact with alcohol to predict violence against women, sexual minorities and intimate partners. Lynn O. Lightfoot is a psychologist in private practice in Oakville, Canada and has worked as

in independent consultant and practitioner for the last 25 years. She has been an adjunct faculty member at Queen’s University and a Lecturer at the Ontario Institute for Studies in Education. She is the author of over 50 scientific articles, book chapters, conference proceedings and government reports in the field of substance abuse. She has specialised in the development and evaluation of substance abuse treatment programmes for forensic populations that have been implemented nationally and internationally. Jan Looman was employed by the Correctional Service of Canada from 1992 until 2015. He

served as the Program Director of the High Intensity Sexual Offender Treatment Program at the Regional Treatment Centre (Ontario) from 1997 to 2011, and was responsible for that xx

Contributors

programme’s accreditation in 2002. He then served as the Clinical Manager for the Regional Treatment Centre (Ontario), a hospital operated by the Correctional Service of Canada until 2015. Currently he is working as a psychologist in the Forensic Mental Health Service of Providence Care Hospital. Evan C. McCuish is an Assistant Professor at Simon Fraser University and is the Project Director of the SSHRC-funded Incarcerated Serious and Violent Young Offender Study, the largest and longest-running study on young offenders in Canada. His research interests include criminal careers, desistance, developmental criminology, foster care, gang involvement, psychopathy, sexual offending and violence. His work is published in the International Journal of Forensic Mental Health, Sexual Abuse: A Journal of Research and Treatment, Justice Quarterly and Journal of Criminal Justice. Shelby Elaine McDonald, PhD, is an Assistant Professor in the School of Social Work at Virginia

Commonwealth University (VCU). She received her PhD in Social Work from the University of Denver. Her research and publications focus on ethnocultural variations in women and children’s exposure and response to intimate partner violence and human–animal interactions in the context of welfare, health and socioecological justice. She has a specific interest in the intersection of children’s exposure to intimate partner violence and concomitant animal cruelty. Her current research uses advanced person-centred statistical techniques to explore heterogeneity of adjustment among children who experience polyvictimisation. Rachel D. MacKenzie is a senior psychologist at Forensicare, the forensic psychiatry provider to

the Australian state of Victoria. Additionally, she works in private practice. She specialises in stalking and sex offences, treating both perpetrators and victims. She is author/co-author of eight book chapters and 15 articles in peer-reviewed journals. She is the lead author of the Stalking Risk Profile (SRP) – the leading manualised instrument for the assessment of risk in stalking and harassment – as well as a co-author of the Communications Threat Assessment Protocol (CTAP) and of the Screening Assessment of Stalking and Harassment (SASH). She has been on the board of the Asia-Pacific Association of Threat Assessment Professionals since its inception. Stephen James Minton is a chartered psychologist and a lecturer in Psychology of Education at the School of Education, Trinity College, Dublin, Ireland, where he serves as the School’s Director of Undergraduate Teaching and Learning. He has extensive experience in the fields of anti-bullying research and practice, focusing over the past decade on the prejudice-related aggression and exclusion directed towards marginalised groups, including indigenous peoples, LGBT people and members of alternative sub-cultures. Among other scholarly works, he is the author of Marginalisation and Aggression from Bullying to Genocide: Critical Educational and Psychological Perspectives and Using Psychology in the Classroom. Randy J. Nelson is a Distinguished University Professor and holds the Brumbaugh Chair in Brain

Research and Teaching at The Ohio State University. He is also Professor and Chair of the Department of Neuroscience. Professor Nelson earned his BA and MA degrees at the University of California, Berkeley. He simultaneously earned a PhD in Psychology and a PhD in Endocrinology from UC–Berkeley, then conducted postdoctoral research in reproductive physiology at the University of Texas, Austin. Professor Nelson served on the faculty at The Johns Hopkins University for 15 years before moving to Columbus. He has published over xxi

Contributors

400 research articles and several books describing studies in behavioural neuroendocrinology, biological rhythms and motivated behaviours, especially aggressive behaviours. Nikola Ninaus graduated with a distinction in the Bachelor of Criminology and Criminal Justice, School of Social Sciences, University of New South Wales (UNSW), Australia, in 2012. She has been employed as a research assistant (RA) in the School of Social Sciences and the School of Psychology at UNSW as well as in the School of Social Sciences and Psychology at Western Sydney University. In her RA roles, Niki has worked on a range of projects covering various criminal justice issues including offender management, elderly offenders, housing, mental health and stalking. Ioan Ohlsson, PhD, is a Chartered Psychologist, Registered Forensic Psychologist and Associate Fellow of the British Psychological Society. He currently works in a senior clinical position within the National Health Service. He was previously one of the lead psychologists working in a secure forensic mental health hospital. He had input into the assessment and treatment of psychiatric patients upon admission and during their period of hospitalisation. Dr Ohlsson has over 14 years’ experience of applied practice and has worked across the lifespan with offenders in the community and in secure forensic settings. He also works part time at the University of Central Lancashire, where he teaches on the MSc Psychology programme and supervises students’ applied research projects. Dr Ohlsson regularly undertakes assessments and delivers evidence-based interventions with individuals and families who present with histories of violence. Karin Österman, PhD, is Associate Professor of Developmental Psychology at Åbo Akademi

University and Adjunct Professor (Docent) of Social Psychology at Helsinki University. She is the Director of a Master’s Programme in Peace, Mediation, and Conflict Research at Åbo Akademi University. Her research includes studies on the physical punishment of children, child abuse, domestic aggression, aggression in the school context and conflict resolution. Rebecca Ozanne is a PhD student at the University of Central Lancashire. She is currently a

research associate and trainee forensic psychologist in a secure setting. Rebecca completed her master’s degree in Forensic Psychology at the University of Central Lancashire. Her research interests include aggression, child abuse, mental health and trauma. Dominic J. Parrott, PhD, is a Professor of Psychology at Georgia State University. His research uses laboratory and survey methods to examine risk factors and mechanisms for aggression perpetration, with a particular emphasis on the effects of alcohol on intimate partner violence, aggression toward sexual minorities and sexual aggression. An end goal of his research programme is to inform directly the development of interventions that prevent or reduce alcohol-related violence. His work has been funded by the National Institute on Alcohol Abuse and Alcoholism and the Centers for Disease Control. Debra J. Pepler is Distinguished Research Professor of Psychology, most familiar for her ongoing research on aggression, bullying and victimisation among children and adolescents. She also conducts research on children in families at risk through Breaking the Cycle – a programme for substance-using mothers and their young children. She has co-authored many books, journal articles, chapters and reports. Together with Dr Wendy Craig, Dr Pepler leads a federally funded national network, PREVNet (Promoting Relationships and Eliminating Violence Network) to promote healthy relationships and prevent bullying for children and youth (www.prevnet.ca). xxii

Contributors

Matthew D. Phillips is an Assistant Professor in the Department of Criminal Justice and Criminology at the University of North Carolina (UNC), Charlotte. His principal research interests include data science, transnational organised crime, terrorism, drug trafficking, drug offending and violence, life course criminology and interactional theory and quantitative and statistical methods. He is also researching the application of big data initiatives to the analysis of crime, particularly within the realm of national security. He has recently published in Intelligence and National Security, Youth Violence & Juvenile Justice, Journal of Criminological Research, Policy and Practice, Journal of Terrorism Research and Journal of Quantitative Criminology. Craig Pinkney is a Lecturer in Youth, Communities and Families and Gangs Programme Leader

with University College Birmingham. He is director of Real ActionUK, an outreach organisation based in Birmingham, which specialises in working with disaffected young people. Craig has over 13 years’ experience as an outreach youth worker, working with some of Birmingham’s most challenging young people, high-risk offenders and victims of gang violence. He has an MA in Criminology and specialises in teaching on youth violence, urban street gangs, extremism, trauma and desistance. Devon L. L. Polaschek’s research interests include theory, intervention and intervention

evaluation with serious violent and sexual offenders, family violence, psychopathy, desistance, reintegration and parole. She is the author of more than 110 journal articles, book chapters and government reports, and a fellow of the Association for Psychological Science. Her research has been supported by a decade of funding from the Department of Corrections, in order to develop a better understanding of high-risk violent male prisoners: their characteristics and what works to reduce their risk of future offending. Robert A. Prentky is Professor of Psychology and Director of Forensic Training at Farleigh

Dickinson University. He has been engaged in research and writing on sexual offenders for 35 years, evaluated or supervised the evaluation of more than 2,000 offenders and has served as an expert witness for over 20 years. He is a fellow of the American Psychological Association and the Association for Psychological Science. Shannon E. Reid is an Assistant Professor in the Criminal Justice and Criminology Department

at the University of North Carolina at Charlotte. Her main research interests are focused on gang-involved and trauma-impacted youth and their interactions with the criminal justice system. Her research has been published in Criminology, Legal and Criminal Psychology, Journal of Interpersonal Violence, Journal of Criminological Research, Policy and Practice, Deviant Behavior and Homicide Studies. Benjamin Roebuck is Professor of Victimology at Algonquin College where he has coordinated the graduate programme for five years. Currently, Benjamin is the principal investigator for a Canada-wide research project on resilience and victims of violence funded by the Social Sciences and Humanities Research Council of Canada (SSHRC). Benjamin’s previous work has focused on youth homelessness, strength-based intervention and local adaptations of evidence-based crime prevention programmes. He serves as the Vice-President of Youth Now Canada, supporting young people with complex needs in the areas of youth justice, housing, community support and engagement in agriculture. Al-Karim Samnani is an Assistant Professor of Management in the Odette School of Business at

the University of Windsor. His primary research interests focus on aggression and bullying xxiii

Contributors

in the workplace and examines its intersection with topics such as diversity, leadership and cognitive and social psychology. He has published a number of articles in reputable journals such as The Leadership Quarterly, Human Resource Management and Organizational Psychology Review, among others. Kathy Sanders, MD is the State Medical Director/Deputy Commissioner of Clinical and Professional Services of the Massachusetts Department of Mental Health. She is a senior psychiatrist in the Department of Psychiatry at Massachusetts General Hospital and is Instructor in Psychiatry for Harvard Medical School. Her areas of focus include violence and aggression, residency training, health and wellness, mindfulness and leadership. Lynn A. Stewart is a registered psychologist and academic working most of her career in Canada’s

federal correctional system. Currently she is a senior research manager where she leads applied research on correctional interventions and women offenders, examining how we can work effectively to reduce offender recidivism within the criminal justice system. She has published on issues related to evidence-based practice including correctional programme outcome studies, domestic violence interventions, indigenous offender specific correctional interventions and women-specific correctional programmes. Recently she has led research on the mental health of offenders and its impact on their institutional and community outcomes. Matthew Valasik is an Assistant Professor of Sociology and Criminology in the Department of

Sociology at Louisiana State University. His primary interests are the socio-spatial dynamics of gang behaviour and problem-oriented policing strategies (e.g., gang units, civil gang injunctions) used by law enforcement. His research can be found in Deviant Behavior, Homicide Studies, Theoretical Criminology, Journal of Criminological Research, Policy and Practice, Rural Sociology and The Oxford Handbook of Environmental Criminology. Irena Colakova Veljanova is a Lecturer in Sociology with the School of Social Sciences and

Psychology, Western Sydney University. She has completed her PhD in the field of Human Welfare Studies and Services. Her research interests include: health sociology, social policy, ethnic, migration and transnational studies, community health, disability studies, critical gerontology and community participatory research. Some of her published works include Health, Agency and Wellbeing and ‘Lifestyle science: Self-healing, co-production and DIY’, Health Sociology Review. Jenny S. West is a doctoral student in the Department of Criminology, Law and Society at the University of California, Irvine. Her research focuses on street gang social networks and group dynamics, patterns of crime displacement and dispute transformation on social media. Jennifer Yang is an honours student with Simon Fraser University’s School of Criminology. Her honours thesis concerns the adult offending outcomes of youth with a history of foster care placement.

xxiv

Preface Human aggression: How far have we come? Jane L. Ireland, Philip Birch and Carol A. Ireland

Monsters exist, but they are too few in number to be truly dangerous. More dangerous are the common men, the functionaries ready to believe and to act without asking questions. — Primo Levi (1919–1987)

It is fitting, in the face of the continuing tragedy of human aggression, to commence with an insightful quote from a survivor of one of the most chilling and horrendous acts of sustained aggression of our time, the Holocaust. Primo Levi, a renowned chemist, writer and Auschwitz survivor authored If This Is Man in 1947, recounting his year spent in Auschwitz, driven by a desire to ensure that the actions of humankind were never forgotten. This was in essence the importance of the work, to act as a means of capturing events and ensuring that no one forgets what humans are capable of. Levi also captures the distinction between being ‘human’ and ‘humanity’, with the latter where our potential for peace, empathy and concern as a species resides. An ability to recall through generations, past events and the horrors of where aggression has sought refuge is both a gift and a curse for humans; we can look back at our past actions and what we have inflicted on others, feel guilt and shame and then try to build our understanding as to why our potential for inflicting harm through aggression continues. The answer to this is not straightforward and is captured well by Primo Levi’s comments. Arguments that aggression is the action of a few damaged or a disordered member of our species (the ‘Monster’) is not accepted as a sufficient explanation for aggression. Undoubtedly there are individuals who through genetic predisposition, social/familial influence or both continue to inflict aggression, but equally there is a potential in all of us to engage in aggression (‘the common men’), given the right circumstances. The mechanism by which these circumstances develop and combine with predispositions to create a fertile environment for aggression is not yet clearly known but there are considerable in-roads into our understanding. We know, for example, that socially there is more acceptance of some acts of aggression over others, leading to a minimisation of aggression in some circumstances and the development of acceptance beliefs. Indirect aggression, where the intention of the act is unclear and the identity of the aggressor(s) potentially unknown, is a salient xxv

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example. Yet, who is to determine that ostracising, spreading rumours and/or malicious gossip (i.e. indirect aggression) is not a concern? It certainly remains so to victims. We further accept that essentially humans are social animals that do operate well within a formed group (e.g. family, friendship circles, tribes) and yet we have seen social grouping acting in a manner that promotes aggression (e.g. gang membership, riots, organised crime syndicates, terrorist groups). Underpinning the human ability to operate within a social group is our evolved skill in being able to quickly place individuals into groups. Take, for example, the classic in-group out-group hostility argument, where humans are thought to be aggressive towards those groups they consider the out-group, with this aggressive tendency somehow determined by evolution. Whereas it is certainly the case that out-groups can be targeted and become the victims of aggression from the in-group, the ability and choice to display aggression towards the out-group is arguably not part of the evolutionary process; evolution has developed our skill at placing other humans into groups but not to display aggression towards them. Our ability to consider the use of aggression towards the out-group is born of other factors, both internal to an individual (e.g. personality, attribution biases) and external (e.g. environmental factors, such as scarce resources). Regardless of the debates that can be had, one undefeated acceptance is that human aggression is a universal behaviour unrestricted by age or sex and one that takes a number of different forms, appearing across a range of contexts. It is not inevitable, but it is a behaviour all are capable of engaging in. Consequently, it is a topic that continues to fascinate scholars and practitioners interested in understanding aggression, in reducing its occurrence and in trying to limit the effects. There have been significant advances made in the last 60 years with regards to how we conceptualise, assess and treat aggression. For example, there has been a move away from focusing purely on more direct forms of aggression that are easily defined (e.g. physical, sexual, verbal) to the subtler forms of indirect aggression. Certain areas that have seen considerable development in the last 15 years include relationship and family violence, our understanding of gang-related control and aggression and also sexual violence. More recently there has been increased consideration and acceptance of gender-neutral understandings of aggression, leading to more consideration of aggression by women. The use of the term human and not mankind is adopted here for this very reason. There has also been a move away from combining antisocial behaviour and aggression as if they were shared concepts, which can lead to an over-focus on criminalised aggression. This is an essential point to draw out – since when was aggression considered criminalised? There are many arguments that can be developed to support the adaptive (and non-criminal) element of aggression; humans are clearly the dominant species on Earth and therefore the most successful. Aggression has not, however, been phased out from our evolution so it must clearly retain an adaptive purpose and cannot be described universally as ‘maladaptive’. It is without doubt that some societies use aggression less than others but regardless of this aggression is retained. The answer concerning the criminalisation of aggression perhaps lies in how human society has developed and where they have drawn moral lines concerning what is and what is not acceptable aggression; assaulting someone in the context of anger is legally and morally wrong, but what of a parent defending their child physically against an adult who is intent on causing their child physical harm? Legally the issue would focus on defensive aggression and the proportionality of the reaction to the aggression displayed in order to determine criminal action, but morally is such aggression deemed acceptable? Most likely yes by the ‘common men [sic]’. Indeed, it is the moral judgement of humankind that has perhaps become the true judge of the acceptability or otherwise of human aggression. The moral lines evolve along with societies’ development. Take, for example, the following reference to the value of duels: xxvi

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A man may shoot the man who invades his character, as he may shoot him who attempts to break into his house. —Samuel Johnson (1709–1784)

Making duels illegal acts is barely 100 years old in some locations and they were often attended by hundreds of spectators. Their aim was to prove courage and settle arguments. They were also conducted with their own codes and designated equipment. They occurred when there was a view that Courts were unable to provide justice. One of the most notable duels was likely that between the US vice-president, Aaron Burr, and a political opponent, Alexander Hamilton, in 1804 that led to the latter being killed. The thought of resolving such political matters through an act of aggression in this manner would draw clear disdain and condemnation where words are now preferred. Equally though, political disputes are clearly still sometimes resolved through aggression (e.g. war, riots) whereas the notion of one individual being allowed to murder an opponent with the blessing of society through the act of a duel is seemingly not. Our Courts certainly now act as the arena where alleged infringements on character are settled, allowing for action to be taken through other routes (e.g. slander, libel action). Equally, individuals may pursue to correct character damage through other means such as social media (e.g. tweeting retorts, blogging defences), all of which introduce the potential for arguably more subtle aggression (e.g. harassment) but would not equate to the social acceptance for killing or seriously injuring someone that was part of a duel. But of course, the question is then how much have we really evolved? We may not engage in socially accepted events such as duels, but we still settle infringements on character through aggressive means but in a more uncontrolled fashion: Certainly dueling is bad, and has been put down, but not quite so bad as its substitute — revolvers, bowie knives, blackguarding, and street assassinations under the pretext of self-defense. —Colonel Benton (1782–1858)

Interestingly, the increasing lack of acceptance of duels is considered in part to have coincided with wars where many young men were lost, leading to society becoming less tolerant of the further loss of young men. One could speculate here that acts of mass violence (i.e. war) were actually indirectly adaptive in preventing some forms of individual violence by allowing humans to protect a valuable reproductive asset; young men. The last 30 years of aggression research have certainly seen more focus on trying to understand how we can understand and define aggression across time, focusing more on the function that this behaviour serves, both at an individual and societal level. It has also led to increased consideration of specific groups that utilise aggression (e.g. gangs, terrorist groups), with developed academic interest into these areas advancing considerably in the last decade. Nevertheless, there is increased acceptance that this is not a topic restricted to ‘special groups’ and the ‘monsters’ that Primo Levi refers to, but rather aggression is a common issue not restricted by population. Of great importance is that no matter how much evolutionary success a species has, behaviours that serve an adaptive purpose will remain. Aggression is arguably one such example of this and our interest in trying to understand it will continue. The first step in achieving this may be to place a hold temporarily on moral judgements of aggression since morality is a human condition. Whether all humans wish to accept it or not we remain animals, part of a larger kingdom of animals, animals that willfully use aggression for adaptive purposes without the gift of moral judgement or empathic concern towards others or wider society. When a cat attacks a mouse, xxvii

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it is not considering the moral judgement of its actions but perhaps enjoying the base level pleasure that is to be gained physiologically from aggression; humans, however, may seek sometimes to remove themselves from other animals and vilify those that engage in aggression as ‘beasts’, ‘animals’ or ‘barbarians’. However, without ‘barbaric’ actions at some point along our evolutionary development it would be difficult to see how humans could have advanced across lands and secured resources from others. Nevertheless, we have a tendency to redraft ourselves as ‘modern’ and not ‘barbaric’ but this does not absolve us of our responsibility to accept that we will continue to use aggression and it will continue to have adaptive components for us. Of course, with advanced cognitive development and a well-honed sense of self and others, humans are certainly allowed to distance themselves from other animals, but not to the point where we fail to recognise that aggressive potential is within all animals, regardless of our evolutionary success in adaptation. Indeed, this is captured well by Primo Levi again who notes the importance of remembering our capabilities for aggression: We must be listened to: above and beyond our personal experience, we have collectively witnessed a fundamental unexpected event, fundamental precisely because unexpected, not foreseen by anyone. It happened, therefore it can happen again: this is the core of what we have to say. It can happen, and it can happen everywhere. —Primo Levi (1919–1987)

The Routledge International Handbook of Human Aggression simply serves to highlight our understanding of aggression by focusing on one of the most interesting species in this regard – humans. It seeks to outline how aggression can be enacted and judged by humans and human societies, and how we can perhaps further our continued evolutionary adaption towards more peaceful actions in circumstances where our aggression is not the most or only adaptive choice. Human aggression is clearly, therefore, a topic of broad appeal with much left to study and understand regarding its development, maintenance and resolution. The need to capture the developments we have made in a text that covers the breadth of contexts where aggression occurs is consequently essential. The Routledge International Handbook of Human Aggression seeks to do this by presenting current opinions on core aspects of relevance to the field that will serve, we hope, as an up-to-date resource for academics and practitioners working in this area. It aims to achieve this through five sections, four that build around general and core areas of developed study and practice (i.e. understandings of general aggression; bullying across contexts; relationship and family violence; sexual aggression) and one capturing more contemporary issues of topical interest such as understanding and appreciating victim responses, considering gang membership, media influence and terrorist activities. The ultimate aim of the Routledge International Handbook of Human Aggression is to promote thoughtful reflection and a critical review of the field to allow us to continue our growth of knowledge concerning how humankind can engage in aggression and/or allow aggression to occur.

References Levi, P. (1947). If This Is Man. Originally published by De Silva and translated into English in 1959. [See also Levi, P. (2005). The Black Hole of Auschwitz. Edited by Marco Belpoliti, Translated by Sharon Wood. Cambridge, UK: Polity Press.] Samuel Johnson quote: see Krystal, A. (2007). ‘En Garde! The history of duelling’, March 12. New Yorker. www.newyorker.com/magazine/2007/03/12 accessed 9 June 2017. Colonel Benton quote: see ‘Duel and dueling’, The Encyclopedia Americana (1920). Chicago, IL. xxviii

Section I

Understanding general aggression

1 The development of aggression in childhood and adolescence A focus on relationships Debra J. Pepler

Research on the development of aggression highlights the central role of relationships in shaping development. Children learn almost everything about themselves, others, and the world through their experiences in relationships (National Scientific Council on the Developing Child, 2004). When children’s relationships fail to support their social-emotional development, aggressive behaviour patterns become consolidated and sustained across time and settings. Emerging research reveals the complex ways in which children’s experiences become embedded in their biology. Therefore, to understand the development of aggression, we need a binocular perspective, integrating one lens focused on individual children’s development and another lens focused on the way in which others interact with children, creating the context for development (Pepler, 2006). This chapter starts with a consideration of the biological foundations for children’s development, followed by a focus on the role of relationships in the development of aggression. Observational and other research sheds light on what does and does not develop in the contexts of the family, peer group, and school. The focus on relationships provides a window into the complex and dynamic mechanisms that shape the development of aggression.

Theoretical perspectives on the development of aggression The theoretical and empirical foundations for research on the development of aggression through childhood and adolescence have expanded remarkably. Since 1994, when I co-authored a chapter on the development of antisocial behaviour (Pepler & Slaby, 1994), there has been growing understanding of the complex and dynamic interplay of biological, psychological, and social processes that shape development. Research on what develops under the skin when children are exposed to unpredictable, harsh, and stressful environments highlights biological processes underlying the development of aggression. Children’s biological inheritance is in constant interplay with their experiences in relationships and together they shape not only children’s behavioural style, but also their emotional character and physical health. Based on an ecological perspective (Bronfenbrenner, 1979) or a developmental-contextual perspective (Lerner, 1995), we have long recognised that children develop within influential contexts including the family, school, peer group, neighbourhood, and broader society. In some 3

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contexts, such as the family, children do not actively choose their relationships. In other contexts, such as the peer group, children are freer to choose – and tend to gravitate to people, activities, and settings where they have positive rather than aversive experiences (Snyder, 2002). The social development model specifies that strong social bonds and positive social development occur when children and youth are raised with positive interactions, positive involvement, adequate skills, and reinforcements for positive behaviours (Catalano & Hawkins, 1996). From an evolutionary perspective, aggression can be adaptive for youth who are skilled in using it to obtain goals with relatively little personal or interpersonal cost (Volk, Camilleri, Dane & Marini, 2012). These individuals are often bi-strategic in using both prosocial and aggressive strategies to maintain dominance and status (Hawley & Vaughn, 2003). Varying theoretical perspectives call into question aggression as a stable trait and suggest diverse pathways in the development of aggression that depend, in part, on the social context in which aggression is exhibited.

Development through relationships Two questions arise in considering the mechanisms in relationships through which children develop aggression: (1) What relationship capacities need to develop and do not develop for these children, and (2) What aggressive tendencies develop instead? Emotional and behavioural regulation is the cornerstone of healthy development, because other capacities depend on regulation (Eisenberg, Valiente & Eggum, 2010). When regulated, children can initiate and maintain prosocial interactions, solve problems flexibly, and move toward a balance of autonomy and relatedness. These behavioural relationship capacities are underpinned by social-cognitive relationship capacities. As they come to understand others and relationships, children develop a theory of mind – recognising that others have thoughts and feelings that underlie their behaviours. With this capacity, children can perspective-take and become empathic, which are precursors to compassion. At the same time, children develop a positive understanding of themselves: a sense of self-worth, competence, and positive identity, recognising that they both matter to and belong with others. They learn to engage morally with others and set boundaries to protect themselves. Children internalise social-cultural norms: if norms favour prosocial behaviour over aggression, they learn that is how they should behave and that is how others should treat them. Children who grow up in dysregulated, hostile, neglectful, or stressful contexts seldom have support to develop these critical relationship capacities. Instead, they develop aggressive behavioural styles, which in the moment may be adaptive, but over time mitigate success at school, in peer relationships, and as productive adults. Growing up in hostile or unpredictable relationships also leads children to view others with hostile attributions. Rather than becoming connected and bonded, these children are at risk of becoming alienated from critical positive relationships. They drift toward relationships in which they are recognised and appreciated – within deviant peer groups, gangs, and other marginalised groups. Prior to focusing on relationship processes, it is important to consider the individual factors that place children at risk for the development of aggression.

Individual characteristics that place children at risk for aggression Epigenetic research has shattered beliefs that inherited biological attributes, such as genes or temperament, are fixed, by revealing the dynamic, complex, and multi-level processes that transform biological processes, such as gene expression (cf. Buschdorf & Meaney, 2015). Genes set parameters for development, but their effects are shaped by the nature of children’s experiences. For example, Naumova and colleagues (2016) examined whether epigenetic mechanisms were 4

The development of aggression

involved in sustaining the effects of negative parenting. Mother–child dyads were followed over 15 years from middle childhood to adolescence and early adulthood. They found significant associations between changes in offsprings’ perception of rejecting parenting from middle childhood to adulthood and DNA methylation in the offsprings’ adult genomes. The findings suggest that changes in methylation, which turns genes on or off, may be a mechanism linking negative parenting and offsprings’ adaptation. Research on gene–environment interactions highlights how children’s genetic vulnerability can be exacerbated by challenging relationships. Liu, Li and Guo (2014) conducted a metaanalysis of gene environment interactions in the development of delinquency and violence. They found that genetic contributions to delinquency and violence could be explained by an environmental triggering or suppressing process: when youth grow up in adverse social conditions, there is a larger genetic contribution to the development of delinquency and violence. Conversely, when youth grow up in favourable conditions with stronger attachments and social controls, there is a smaller contribution by the genes linked to delinquency and violence. Temperament has long been considered key in the development of aggression (Loeber & Hay, 1997). Problems emerging in the first weeks and months of life can set up patterns of interaction that persist through relationships and across contexts. For example, infants with difficult temperaments are difficult to soothe and tend to be highly reactive. These children present challenges for parents’ attempts to regulate and manage their behaviours. Vitaro and colleagues found that a difficult temperament in infancy was positively related to reactive aggression in kindergarten (Vitaro, Barker, Boivin, Brendgen & Trembley, 2006). In addition, harsh parenting was related to the development of both reactive and proactive aggression. Emerging research is clarifying how children’s experiences in relationships shape genetic expression, which is integrally and dynamically linked to brain development (Meloni, 2014). When children live in a chaotic or non-nurturing environment it can disrupt brain development, neuronal functioning, and connectivity, which in turn may underlie the propensity to be aggressive (Lösel & Farrington, 2012). Given the plasticity of development, these neural disruptions can be ameliorated. In a study of aggressive children referred to the SNAP® program (Stop Now and Plan program), Lewis and colleagues (2008) found that their brain activation differed from that of non-aggressive children in the ventral and dorsal regions indicating poorer executive functioning. Following treatment, children with behavioural improvements also showed brain activity that was similar to the non-aggressive children, suggesting increased functioning and connectivity had developed through the program. Both aggressive children and their parents participate in the program and learn regulation and problem-solving skills; therefore, changes may emerge simultaneously in the children, parents, and family context.

Relationships in the development of aggression With increased understanding of what is happening under the skin when children are exposed to adverse relationships, we next focus on what is happening in repeated interactions within those relationships that shapes not only genetic expression and brain development, but also social and emotional development. Focusing on the relationship experiences of children begins to elucidate the dynamic mechanisms that shape the development of aggression within the proximal contexts of the family, peer group, and school. We can consider what children are learning in the moment that supports the development of skills and the capacity for relationships or, conversely, undermines healthy development. Baumrind (1991) identified two dimensions of parenting that promote optimal development: providing responsive love and guiding, and setting expectations and limits for children’s 5

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behaviours. Research suggests that children require these forms of adult support across all contexts (e.g., day-care, schools, community organisations, sports). In a review of protective processes, Lösel and Farrington concluded that: “an emotionally warm, attentive, accepting, norm-oriented supervising and structure-giving upbringing encourages the positive development of children” (2012, p. S14). They note that these positive practices, which align with Baumrind’s model, also mitigate the development of violence in the face of risk. Drawing from research on children’s relationships across family, peer, and school contexts, we can begin to piece together a picture of how relationship experiences accumulate to undermine healthy development and divert children onto aggressive developmental pathways. As Dodge and colleagues (2009) noted, the combination of child vulnerabilities and adverse social contexts sets up a developmental cascade of failure and risk for antisocial and illegal behaviours. In the following section, the mechanisms through which this developmental cascade occurs are considered.

What critical relationship capacities do not develop and what problematic behaviours do develop through relationships? Without the benefit of nurturing relationships, children may fail to develop capacities that are essential for engaging in and sustaining positive relationships including: (1) a positive orientation in relationships, (2) emotional and behavioural regulation, (3) prosocial behaviour and problem solving, and (4) understanding of and concern for others. Next research is considered that points to the failure of relationships to support the development of these capacities, which involves not only children’s lack of skill development, but also how others support or fail to support children’s healthy development, respond, and create processes that support the development of aggression. Positive orientation in relationships

To become effective social beings, children need to develop a positive orientation to others and a sense of enjoyment in the company of others. Given reciprocity in relationships, others need to think positively about and like being with these children (Pepler, 2006). The dynamic mechanisms shown to undermine aggressive children’s positive experiences of relationships within the family, peer group, and school are important. Family processes. Children’s social lives begin with attachment processes to primary caregivers. When children are well nurtured, they come to understand that they can trust others, give and receive from others, and sustain relationships through disruptions. Parents’ behaviours shape children’s perceptions of relationships, which in turn shape their cognitive, emotional, and behavioural functioning in relationships (Moretti & Obsuth, 2013). Children who develop aggression in the preschool years are likely to have insecure attachments with their parents (Speltz, Deklyen & Greenberg, 1999). Buist and colleagues found similar links for adolescents between negative experiences in relationships with their parents and aggressive and delinquent behaviours (Buist, Dekovic´, Meeus & van Aken, 2004). The links between negativity in the mother–child relationship and children’s aggression can be bi-directional. Zadeh and colleagues found that mothers’ negativity influenced children’s aggressive (externalising) behaviour over time; however, the impact of children’s aggressive behaviours on mothers’ negativity was stronger than the reciprocal effect. In addition, children’s influences on their mothers became stronger as the children grew older (Zadeh, Jenkins & Pepler, 2010). When parents and children do not have positive perceptions and relationships with each other, their interactions become increasingly strained. Smith, Dishion, Shaw and Wilson (2015) 6

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studied parents’ relational schemas regarding how they understand and react to their children’s behaviours. With a negative schema, parents interpret children as purposefully provoking or resisting them. Parents’ negative schemas were linked to coercive parent–child dynamics and to children’s oppositional and aggressive behaviours five and six years later in middle childhood. These findings suggest that when parents lack positive orientations in relationships with their children, children become non-compliant and develop aggressive behaviour problems, perhaps as a function of their own negative relational schemas. Trentacosta and Shaw (2008) found that the effects of early parent–child relationship problems are long lasting: rejecting parenting in early childhood predicted antisocial behaviour in early adolescence. Peer processes. Children are positively motivated to interact with peers even when they have weak family attachments. In observations on the school playground, we found that aggressive children initiated more interactions with their peers than non-aggressive children (Pepler, Craig & Roberts, 1998). Contrary to expectations, aggressive children spent as much time as nonaggressive children interacting with peers. Conversely, peers were equally interactive with aggressive and non-aggressive children; however, aggressive children were more likely to respond antisocially to peer initiations. In adolescence, aggressive youth tend to have friends with similar antisocial attitudes and behaviours, leading to increases in antisocial behaviour through deviancy training (Dishion, Spracklen, Andrews & Patterson, 1996). A similar process occurs as aggressive youth seek romantic partners: both boys and girls who bully start dating earlier and are more advanced in dating than non-bullying adolescents (Connolly, Pepler, Craig & Taradash, 2000). Youth who bullied, however, view their friends and romantic partners less positively and equitably than non-bullying youth (Connolly et al., 2000). In the case of peer relationships, therefore, a positive orientation to peers may promote and maintain the development of aggression, rather than mitigate it. Although aggressive children may be eager to belong in a peer group, they are frequently rejected by peers – their disruptive behaviours make it difficult for peers to like and play with them. Aggressive children are frequently rejected by unfamiliar peers (Dodge, 1983). Their physically and verbally aggressive behaviour, exclusion of peers, and inappropriate play may elicit peer disliking. As with reciprocal effects in parent–child interactions – children’s aggression exacerbates peer relationship problems and peer relationship problems exacerbate aggressive children’s dysregulation and negative relationship schemas. When rejected, aggressive children tend to drift to the margins of the social group, where they are accepted by other aggressive and rejected children. Within this peer context, they tend to develop increasingly troublesome behaviours through deviancy training (Dodge, Dishion & Lansford, 2006). School processes. Aggressive children are generally unprepared for the academic, behavioural, and social demands of school, leading to a range of problems. Aggressive children begin to develop strained relationships with teachers starting at school entry and increasing over the school year (Doumen et al., 2008). If students are not engaged with school and attached to teachers, they tend to struggle academically, as well as socially, morally, and behaviourally (Kuperminc, Leadbeater & Blatt, 2001). Aggressive behaviour problems may be both the cause and consequence of weak bonds to school (Hoffman, Erickson & Spence, 2013). When students are disengaged, their negative orientation may foster strained relationships with school staff and peers alike. When teachers have a low preference for students, it leads not only to declining grades, but also to increased loneliness at school (Mercer & DeRosier, 2008). The experiences of being rejected by both staff and students may underlie youths’ disengagement. There is mounting evidence that the process of disengagement starts at school entry and comprises the primary developmental process that underlies antisocial behaviour, school failure, and dropout rates (Hirschfeld & Gasper, 2011). 7

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Emotional and behavioural control

The ability to control emotions and behaviour develops through childhood and adolescence and is essential for most activities, especially in times of stress. Aggressive children tend to have limited capacity to regulate, which is elicited and impeded by complex relational processes within the family, peer group, and school. Family processes. Families that struggle to provide the essential elements of love and guidance (Baumrind, 1991) tend to fail in scaffolding for children’s social-emotional development. Through observational research, Patterson (1982) identified coercive processes as a key mechanism in the development of aggression. In coercive processes, either the parents, children or both use dysregulated and aversive behaviours to gain short-term control over the other’s behaviour. In this dynamic, children act so disruptively that parents give up asking for compliance or parents act so disruptively that children finally comply, at least momentarily. Patterson postulated that as these coercive moment-to-moment interactions accumulate, children learn that sustaining disruptive behaviours can be successful in getting parents to withdraw demands. With limited guidance to develop emotional and behavioural regulation, children learn that aggression can be effective. Parents learn that their children are increasingly difficult and better left alone or rejected, at least in the moment. Granic and Lougheed (2016) revisited Patterson’s theory and proposed that parents’ unpredictable switches between permissive and hostile responses elicit anxiety in children, which in turn triggers aggressive behaviour. They note that as children move into peer relationships and school, their difficulties in the family further exacerbate anxiety, which may elicit aggressive outbursts that function to regulate distressing emotions. Dysregulated parent–child dynamics have been identified in many studies of children’s aggression. Becht and colleagues (2016) examined links between parents’ over-reactivity and girls’ and boys’ trajectories of aggression and rule breaking from childhood to adolescence. They defined over-reactive parenting as tendencies to respond with anger, frustration, and meanness to children’s problem behaviour. They found three developmental trajectories for aggression: low decreasing, high decreasing, and high increasing. Youth in the high increasing and high decreasing aggression trajectory groups had parents with higher over-reactivity than those in the low trajectory group. Becht and colleagues note that parents’ over-reactivity may create an unpredictable and inconsistent environment for children. Consistent with coercion theory, they noted that over-reactive parents may negatively reinforce children’s aggressive tendencies by taking away demands when children respond to them with hostility, which predisposes children to develop high levels of aggression over time. Family interactions also contribute to children’s lack of self-regulation. Meldrum and colleagues (2016) studied boys’ self-control and aggression in relation to parents’ self-control and ineffectiveness (harsh punishment and ability to structure for the child). They found that over time mothers’ ineffective parenting was linked to their sons’ aggression through the boys’ low levels of self-control. Furthermore, mothers’ self-control was not directly related to children’s self-control, rather it was mediated through parenting ineffectiveness. Similar to mothers, fathers’ self-control was negatively related to effective parenting, but did not significantly relate to boys’ self-control and aggression. From a developmental perspective, this study suggests that boys fail to develop self-control because their mothers have low self-control, which makes them ineffective parents. In addition, mothers’ harsh punishment and lack of positive structuring was linked to boys’ aggression. Peer processes. Within peer groups, interactional processes can contribute to aggressive children’s struggle to achieve emotional and behavioural regulation. Our observations revealed that aggressive children have less predictable interaction styles than non-aggressive children 8

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(Pepler et al., 1998). They exhibit more mixed behaviours in which they initiate an aggressive (or prosocial) behaviour, fail to wait for a response, and immediately switch to a prosocial (or aggressive) behaviour directed at a peer. With unpredictable switches between prosocial and aggressive behaviours, classmates likely perceive aggressive children as difficult. Given aggressive children’s dysregulated interactional style, other children may actively avoid playing with them, eliciting subsequent feelings of rejection and shame that further compromise the development of emotional and behavioural regulation. As children move into peer relationships and school, their difficulties in these contexts can further exacerbate anxiety in social interactions. Granic and Lougheed (2016) contend that when children experience contempt from peers and subsequent shame, they often react with anger and aggression. These reactive behaviours can serve to override distressing emotions of anxiety and shame, thereby mitigating the development of emotional and behavioural regulation. School processes. School readiness comprises three domains: emotional self-regulation, social competence, and family/school involvement (Webster-Stratton, Jamila Reid & Stoolmiller, 2008). When children enter school, there are new, explicit expectations for emotional and behavioural regulation. Children who exhibit aggressive behaviour upon school entry often lack regulatory capacities for sustained attention and behavioural control, which are essential for academic success. Aggressive children tend to be disruptive and engage in bullying behaviours in the classroom (Atlas & Pepler, 1998). These troublesome behaviours may elicit increased negative attention from both teachers and their classmates. For aggressive children at school, as in the home, negative attention may be more reinforcing than no attention at all. When children are genetically vulnerable to be aggressive, they are at increased risk for relationship problems at school. Brendgen and colleagues (2011) found that children who were genetically vulnerable to be aggressive were at risk of being victimised by their peers. Their relationships with teachers moderated peer relationships. When aggressive children had positive relationships with teachers, they were less likely to be victimised by peers; when they had high conflict and low closeness with teachers, they were more likely to be victimised by peers. Brendgen and colleagues raised concern for the transactional nature of these relationship dynamics. Children’s genetic vulnerability to be aggressive can elicit victimisation from peers, which may lead to more aggression, creating vicious cycles of increasing mutual aggression between vulnerable children and their peers. There is growing evidence that experiences of victimisation can lead to bullying. Without adequate emotional and behavioural regulation, children may be highly reactive when bullied, which can lead to further victimisation and reactivity. We found a sequential relationship between aggression and victimisation: when youth started to be victimised, they started to become aggressive and bully others (Goldbaum, Craig, Pepler & Connolly, 2003). Children who are chronically victimised may model aggressive strategies from those whom they view as more powerful. Furthermore, they may begin to bully as a way of coping with the anxiety and hostility elicited by being victimised.

Prosocial behaviour and problem solving In her poem, Children Learn What They Live, Dorothy Law Nolte (1972), highlighted the central role that relationship experiences play in children’s development: “If children live with criticism, they learn to condemn. If children live with hostility, they learn to fight. . . . If children live with sharing, they learn generosity . . . If children live with fairness, they learn justice.” In the following section, we consider the challenges and dynamic mechanisms within the family, peer group, and school that impede the development of prosocial behaviours and effective problem solving. 9

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Family processes. Children growing up in dysfunctional families, with few models of prosocial behaviour and positive problem solving, will learn what they live. Living with inter-parental violence and child maltreatment are two cogent and stressful experiences that impact children. Gustafsson and colleagues (2014) examined the relative influence of inter-parental violence and physical maltreatment on children’s behaviour problems at school entry. They found that both types of family violence had a unique negative influence on children’s functioning. It is likely that both the modeling and the stress that children experience through family violence undermine the development of prosocial behaviour and positive problem solving. Ineffective problem solving often arises from inflexibility and negative dynamics. Granic and colleagues assessed the problem-solving of mothers and aggressive children before and following the SNAP® program (Granic, O’Hara, Pepler & Lewis, 2007). They compared dyads in which children improved through treatment with those who did not improve. After treatment, dyads in the non-improved group failed to show increases in flexible problem-solving, but increased in time spent “stuck” in one emotional state. Although dyads in the improved group still expressed negative emotions, they acquired skills to repair conflicts and to shift from negative interactions to mutually positive patterns. In a complementary study assessing changes in aggressive children through the SNAP® program, Lewis and colleagues (2008) found that children who had improved through treatment showed a reduction in ventral prefrontal activation at the time when inhibitory control was required. They speculated that for aggressive children with comorbid anxiety, the anxiety-related mechanisms may be primary, with aggressive behaviour modulating anxiety. With strained relationships, children may be unmotivated to interact prosocially and positively. Many have noted that children’s motivation to meet adults’ expectations depends on the quality of their relationships. Kochanska and colleagues found that mothers’ responsiveness to their children was linked to their children’s willingness to comply with requests (Kochanska, Kim, Boldt & Yoon, 2013). When adults are attuned, children may have a sense of being relevant and valued; therefore, respond appropriately to sustain adults’ positive regard. McKinnon (2008) has written about this dynamic in his clinical work with substance-addicted youth. He noted that until youth know that you “recognise”, value, and understand them, they are resistant to clinical guidance. Peer processes. Peer interactions can contribute to the lag in acquiring prosocial behaviours and problem solving. Our observations of bullying provide evidence for peer dynamics that promote aggressive behaviours, rather than prosocial ones. We found that peers were present in 85 per cent of bullying episodes and they spent 75 per cent of the time paying attention to the child who was bullying (Craig & Pepler, 1997). Peers played an active role in exacerbating aggression: when a peer joins in bullying, the child who initiated the bullying becomes increasingly aggressive and aroused (O’Connell, Pepler & Craig, 1999). Furthermore, negative peer influences are bi-directional: bystanders are more likely to join bullying when incited by the child who initially bullied (O’Connell, Pepler & Craig, 1999). In these ways, peers fail to contribute to prosocial behaviours and are highly reinforcing of aggressive behaviours. Peers tend to respond negatively toward aggressive children. Because aggressive children initiate aggression more frequently than non-aggressive children, they are on the receiving end of retaliation more often than peers (Pepler et al., 1998). Hence, aggressive children’s peer interactions not only elicit and maintain antisocial behaviours, but also fail to promote prosocial behaviours. At the margins of the peer group, aggressive children have restricted opportunities to be with prosocial peers. Instead, they interact with other marginalised peers, who also tend to be aggressive and disruptive. Having aggressive friends creates problems: youth who maintained high levels of bullying over elementary and high school were significantly more likely than nonbullying students to have friends who also bullied (Pepler, Jiang, Craig & Connolly, 2008). 10

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Similarly, Adams and colleagues found that highly aggressive children who had an aggressive friend remained aggressive during the following year. Conversely, those who were initially aggressive and had non-aggressive friends were less likely to be aggressive in the following year (Adams, Bukowski & Bagwell, 2005). These findings are consistent with deviancy training among aggressive children, but also suggest that non-aggressive friends can help promote the development of prosocial behaviour and positive problem solving. In their seminal review of negative peer influences, Dishion, McCord and Poulin (1999) concluded that high-risk youth are susceptible to deviancy training with peers and that friendships among deviant peers predict increases in delinquency, substance use, violence, and maladjustment in adulthood. They highlighted two deviancy training mechanisms: problem behaviours increase when youth are reinforced for deviant behaviour by peers; high-risk youth come to value deviance and become increasingly motivated to engage in problem behaviour. School processes. For children who have not developed prosocial behaviours and positive problem solving, society depends on schools to be the socialising institutions and pick up where parents left off. Children who lag in social-emotional development are at risk, not only because of their deficits in a wide range of communication, social, and cognitive capacities, but also because of the ways that others interact with them, further constraining them to a troubled pathway. Aggressive, disruptive and non-compliant children are difficult to teach and manage. When teachers are not highly attuned to the needs of challenging children and mindful of their own responses to these children, it may be especially difficult to support prosocial development. As Boyce and colleagues (2012) have shown, teachers’ child-centred practices buffer the psychosocial difficulties of children who are vulnerable. When teachers create supportive classroom climates for vulnerable children, the deleterious effects of being marginalised within the peer group are mitigated. These findings led Boyce and colleagues to call for “more supportive, egalitarian, and generous social environments” (2012, p. 17171). In contrast, when teachers actively model low liking of aggressive students, other classmates increase in their dislike and rejection of aggressive students (Mercer & DeRosier, 2008). When actively rejected, aggressive children have few opportunities and reinforcements to respond prosocially and effectively when confronted with social problems. If aggressive children are further marginalised by being removed from mainstream classrooms and aggregated in special “behavioural” classes, deviancy training tends to flourish and students’ problem behaviours are exacerbated (Dodge et al., 2006). As leaders in the classroom, teachers shape the social climate and students’ relationships. If the classroom climate is negative, aggressive children may struggle to develop positive peer relationships and the requisite social skills. In a longitudinal study, Sprott (2004) found that youth who developed violent behaviours during early adolescence had often been in elementary school classrooms with limited emotional support from teachers and classmates. School relationships, however, can be protective and supportive for students with troubled family relationships if these students can become engaged and develop a positive attitude and attachment to school (Sprott, Jenkins & Doob, 2005). Understanding of and concern for others

Children’s social understanding and concern for others develop through relational experiences that help them gradually understand themselves and differentiate themselves from others (Hoffman, 2001). Children with aggressive behaviour problems often fail to develop positive expectations of others (Dodge, 2006) and the moral understanding that underlies positive behaviours (Bandura, 1999). This section focuses on the dynamic mechanisms within the family, peer group, 11

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and school that may undermine aggressive children’s development of understanding and concern for others. Family processes. Dysfunctional family processes contribute to the development of a hostile social-cognitive style (Dodge, 2006). In the early years, if attachment processes are disruptive, children fail to develop trust and mutually positive interactions. With harsh punishment and maltreatment, children learn that others cannot be relied on to interact positively, so they come to expect hostile interactions. In these dynamics, parents not only model aggression, but may also express hostile attributions about their children’s behaviours. Through ongoing hostile interactions within the family, children come to interpret parents’ behaviours as arising from hostile intent and then transfer these attributions to the behaviours of others. Longitudinal research reveals that hostile attributional biases, developed in the early years at home, are linked to aggressive behaviour problems many years later in school (Dodge, Pettit, Bates & Valente, 1995). It follows that if children learn that others are likely to be hostile, they tend to react with hostility and aggression. Moral understanding and concern for the impact of one’s behaviours on others develop through childhood and adolescence. In the early years, children’s behaviours are regulated by the expectations of adults. If they are raised with consistent modelling and expectations of what is right and wrong, they come to understand these standards and behave accordingly (Bandura, 1999). In dysfunctional families with harsh parenting, inconsistent reinforcement patterns, and limited scaffolding for social understanding, children lack critical building blocks for moral reasoning and behaviour. As Bandura has described, moral disengagement develops when children learn to: (1) justify their hurtful behaviour, (2) ignore or minimise the consequences of their hurtful behaviour, and (3) attribute blame to the person whom they have hurt. As discussed in the peer section next, the lack of understanding and concern for others can lead to bullying and problems in peer relationships. Children who live with inter-parental violence may learn that interpersonal aggression is both justifiable and acceptable. In a study of children living in a shelter following exposure to intimate partner violence, Jouriles and colleagues (2014) found that children’s beliefs about the justifiability of aggression were positively associated over time with aggressive behaviour problems. Children’s fears and worries about their mothers’ conflict with intimate partners also related to their aggressive behaviour problems. Whereas some mothers are able to maintain positive parenting, others struggle under the burden of abuse. If abused mothers report frequently using insults with their children, their children are three times more likely to have serious clinical problems than children whose mothers never used insults (Moore & Pepler, 2006). When children are chronically exposed to the stress of inter-parental hostility, they may be particularly vulnerable to their mothers’ disparaging comments, leading to insecurity, self-blame, and acting out behaviours. Peer processes. In his early research on aggressive children’s social cognitive processes, Dodge (1980) created scenarios in which a peer’s intent could be interpreted as hostile, benign, or ambivalent. Compared to non-aggressive children, aggressive children interpreted ambivalent behaviour as more hostile. Observations of aggressive children’s peer interactions suggest that their tendency to infer hostile intent may reflect their lived experiences, which are relatively more hostile than those of their non-aggressive peers. Although peers did not respond differentially to the antisocial behaviours of aggressive and non-aggressive children, aggressive children initiated more antisocial behaviours and, therefore, received more antisocial responses (Pepler et al., 1998). Negative peer interaction dynamics on the school playground may contribute to an understanding that aggression is one of the hazards of everyday life and useful as a means for interpreting and solving social problems. 12

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When children lack understanding of others, they may be less able to synchronise their behaviours within the peer group, adding to their peer relationship difficulties. In a longitudinal study of the development of aggressive behaviour problems between grades 4 and 8, Ettekal and Ladd (2015) found that children who were consistently high on both relational and physical aggression had the most strained peer relationships, with few reciprocated friends and a high likelihood of being rejected by peers. They noted that these children may have had socialcognitive and emotional deficits. Without being able to interpret how peers perceived them and adjust accordingly, they continued to behave aggressively to an extent that was not accepted by peers. Ettekal and Ladd (2015) inferred that these children were not using aggression strategically and beneficially. Furthermore, aggressive children’s peer relationships worsened over time, with decreasing friendships and increasing levels of peer rejection, suggesting the bi-directional relationship processes that cumulatively constrain aggressive children on a troubled pathway. For aggressive children, the experience of being increasingly marginalised and isolated in the peer group may contribute to their lack of social attunement and synchrony. Building on Dodge’s research on hostile attributions, Downey and colleagues examined whether negative attributions are motivated by children’s expectations of rejection by peers. They identified “rejection sensitivity” as the defensive tendency to expect, readily interpret, and overreact to social rejection (Downey, Lebolt, Rincón & Freitas, 1998). Over time, children who were sensitive to rejection increased in disruptive, oppositional, and conflict behaviour. These children had difficulties with both peers and teachers with increasing absences, suspensions, and disengagement from school, as well as poorer grades. Aggressive children appear to develop a hypervigilant and hostile perspective of those in their proximal environments, which arises from their experiences within relationships. Aggressive children may also develop strategies to disengage morally from their own hurtful behaviours. Both Menesini and colleagues (2003) and Hymel and colleagues (2005) have shown that children who bully reason with some of the moral disengagement strategies identified by Bandura (1999). They are more likely to justify their hurtful behaviour by minimising personal advantages (Menesini et al., 2003) and attribute blame to the person whom they have hurt (Hymel, Rocke-Henderson & Bonanno, 2005). Bandura (1999) noted that the process of moral disengagement is gradual; however, a consideration of the bi-directional peer processes that marginalise and alienate aggressive children sheds light on the potential social and cognitive mechanisms that underlie the entrenchment of aggressive behaviour problems. School processes. As indicated previously, children who develop aggressive problems over the early years may lag in their understanding and concern for others. At school entry, there is an expectation that children will be ready not only academically, but also socially and emotionally. Although schools provide systematic scaffolding for the development of literacy and numeracy skills, the inclusion of specific supports for social-emotional learning is just beginning (Collaborative for Academic, Social, and Emotional Learning: CASEL, 2015). Without essential regulation, attentional, and social skills, children with aggressive behaviours are likely to experience repeated failure in both academic and social spheres. In contrast to their peers who move through school relatively smoothly, children who lack the capacities for school performance fall increasingly behind. With experiences of failure in these important life tasks, aggressive children are less likely to become engaged not only in their studies, but also in protective relationships with teachers and peers. The process of disengaging from school cognitively, emotionally, and behaviourally unfolds gradually over the school years. In a study examining engagement, delinquency, and school dropout, Wang and Fredricks (2014) found that dropping out of school is predicted by lower behavioural and emotional engagement and higher problem behaviours. As a result, the most 13

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vulnerable youth in society become truant and eventually drop out of school. The process of disengagement leading to truancy and dropout is dynamic, bi-directional, and embedded in the relationships at school. In a study of school leavers, Ferguson and colleagues (2005) found that relationships figured prominently in students’ perceptions of why they dropped out of school. Many youths who had dropped out reported receiving both direct and indirect messages from principals, vice-principals, teachers, and guidance counsellors indicating that they were not wanted in the school. Relationships with other students were also strained and perceived as contributing to the process of disengagement. According to Ferguson and colleagues (2005), “young people described troubled school cultures due to severe and ongoing bullying and violence. When these issues were not clearly and swiftly addressed, students began the process of skipping school, detentions, suspensions and early leaving” (p. 27). Given that children with aggressive behaviour problems drift to the margins of the peer network, where they associate with other marginalised children, it is not surprising that they develop hostile attributions about their school experiences.

Conclusion This chapter has aimed to build an understanding of the complex and dynamic processes that contribute to the development of aggressive behaviour problems. Biological and social processes interact inseparably to shape the development of aggression. With an increasingly comprehensive understanding of the individual and relationship processes that contribute to the development of aggressive behaviour problems, a critical question is what can be done to prevent and address these problems. Interventions have come a long way in the last 30 years. In the 1980s, aggressive children were perceived as “deficient in many of the social and social-cognitive skills required for successful peer interactions” (Pepler, King & Byrd, 1991, p. 361); therefore, interventions focused only on children to ‘fill them up’ with skills they were lacking. Current evidence-based interventions for children with aggressive behaviour problems, such as the Stop Now and Plan program (SNAP®; Augimeri et al., 2007) are developmental, systemic, and relational. There is a widespread understanding that to sustain any improvement through treatment, changes in developmental contexts and processes are essential. Kazdin (1997) identified parent training as the most effective means of intervening with aggressive children. The question then arises: Whose responsibility is it to support families in effective child rearing and how is this best done? Many parents of aggressive children grew up in strained and stressful families and lacked models of positive nurturing. If society failed them by not providing safe and supportive contexts for their development, does the responsibility now rest with society to support those who are struggling to raise healthy children? With a growing understanding of how aggressive behaviour problems develop, there has been an increased focus on the role of healthy relationships in promoting healthy development. In their article on the critical role of nurturing environments for promoting human well-being, Biglan and colleagues (2012) identified five communication and marketing strategies for broad social-cultural change. These include: 1. Mobilizing relevant national organizations to influence local action, 2. Forging a widely shared view of the societal change needed, 3. Using media to influence individual behaviour and organizational and policy change, 4. Diffusing practices at the local level to support change efficiently, and 5. Creating a surveillance system that focuses attention on the targeted change and indicates what works and what does not. p. 264 14

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In Canada, the author and colleagues have worked collectively within a multi-sector national network (Promoting Relationships to Eliminate Violence Network, PREVNet www.prevnet. ca) to mobilise efforts that align with these five strategies for social change (Pepler et al., in press). We have indications that our nationwide collaborative efforts over the past 10 years are beginning to prevent and address aggressive behaviour problems: the proportion of students who report bullying others has decreased by 62 per cent and the proportion of students who report both bullying others and being victimised has dropped by 44 per cent. The proportion of students who report being victimised, however, has increased by 16 per cent over this time (Craig, Lambe & McIver, 2016). A focus on relationships highlights the potential moment-to-moment experiences in the lives of children with aggressive behaviour problems that either engage and support their positive development or accumulate to alienate them and enable them to drift away from potentially protective relationships. Over the past few decades there have been great strides in research and practice related to the development of aggression and the rates of youth violence have decreased. Nevertheless, there are children and youth in society who are vulnerable and often very challenging. These are the children who need to be identified early and supported across all contexts in their lives, with both nurturance and guidance to promote their social-emotional development and their capacity to engage in healthy relationships for healthy development through the lifespan.

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Catalano, R. F. and Dawkins, J. D. (1996). ‘The social development model: A theory of antisocial behavior’. In J. D. Dawkins (Ed.), Delinquency and Crime: Current Theories. Cambridge: Cambridge University Press, pp. 149–197. Collaborative for Academic, Social, and Emotional Learning (CASEL). ‘Policy recommendations to sustain SEL’. Retrieved on February 17, 2015 from www.casel.org/policy/recommendations Connolly, J., Pepler, D., Craig, W., and Taradash, A. (2000). ‘Dating experiences of bullies in early adolescence’. Child Maltreatment, 5: 299–310. Craig, W. and Pepler, D. (1997). ‘Observations of bullying and victimization in the schoolyard’. Canadian Journal of School Psychology, 2: 41–60. Craig, W., Lambe, L., and McIvor, T. (2016). ‘Bullying and fighting’. In J. G. Freeman, M. King, and W. Pickett (Eds), Health Behaviour in School-Aged Children (HBSC) in Canada: Focus on Relationships. Public Health Agency Canada. Retrieved from http://healthycanadians.gc.ca/publications/scienceresearch-sciences-recherches/health-behaviour-children-canada-2015-comportements-sante-jeunes/ index-eng.php Dishion, T. J., McCord, J., and Poulin, F. (1999). ‘When interventions harm: Peer groups and problem behavior’. American Psychologist, 54: 755. Dishion, T. J., Spracklen, K. M., Andrews, D. W., and Patterson, G. R. (1996). ‘Deviancy training in male adolescent friendships’. Behaviour Therapy, 27: 373–390. Dodge, K. A. (1980). ‘Social cognition and children’s aggressive behavior’. Child Development, 51: 162–170. Dodge, K. A. (1983). ‘Behavioral antecedents of peer social status’. Child Development, 54: 1386–1399. Dodge, K. A. (2006). ‘Translational science in action: Hostile attributional style and the development of aggressive behaviour problems’. Development and Psychopathology, 18: 791–814. Dodge, K. A., Dishion, T. J., and Lansford, J. E. (2006). ‘Deviant peer influences in intervention and public policy for youth’. Social Policy Report, 20. Dodge, K. A., Malone, P. S., Lansford, J. E., Miller, S., Pettit, G. S., and Bates, J. E. (2009). ‘A dynamic cascade model of the development of substance use onset’. Monograph of the Society for Research in Child Development, 74: vii–119. Dodge, K. A., Pettit, G. S., Bates, J. E., and Valente, E. (1995). ‘Social information-processing patterns partially mediate the effect of early physical abuse on later conduct problems’. Journal of Abnormal Psychology, 104: 632–643. Doumen, S., Verschueren, K., Buyse, E., Germeijs, V., Luyckx, K., and Soenens, B. (2008). ‘Reciprocal relations between teacher–child conflict and aggressive behavior in kindergarten: A three-wave longitudinal study’. Journal of Clinical Child & Adolescent Psychology, 37: 588–599. Downey, G., Lebolt, A., Rincón, C., and Freitas, A. L. (1998). ‘Rejection sensitivity and children’s interpersonal difficulties’. Child Development, 69: 1074–1091. Eisenberg, N., Valiente, C., and Eggum, N. D. (2010). ‘Self-regulation and school readiness’. Early Education and Development, 21: 681–698. Ettekal, I. and Ladd, G. W. (2015). ‘Costs and benefits of children’s physical and relational aggression trajectories on peer rejection, acceptance, and friendships: Variations by aggression subtypes, gender, and age’. Developmental Psychology, 51: 1756–1770. Ferguson, B., Tilleczek, K., Boydell, K., Rummens, J. A., Edney, D. R., and Michaud, J. (2005). Early School Leavers: Understanding the Lived Reality of Student Disengagement from Secondary School. Report submitted to the Ontario Ministry of Education and Training, Special Education Branch. Goldbaum, S., Craig, W. M., Pepler, D., and Connolly, J. (2003). ‘Developmental trajectories of victimization: Identifying risk and protective factors’. Journal of Applied School Psychology, 19: 139–156. Granic, I. and Lougheed, J. P. (2016). ‘The role of anxiety in coercive family processes with aggressive children’. In The Oxford Handbook of Coercive Relationship Dynamics. Oxford, UK: Oxford University Press, p. 231. Granic, I., O’Hara, A., Pepler, D., and Lewis, M. D. (2007). ‘A dynamic systems analysis of parent–child changes associated with successful “real-world” interventions for aggressive children’. Journal of Abnormal Child Psychology, 35: 845–857. Gustafsson, H. C., Barnett, M. A., Towe-Goodman, N. R., Mills-Koonce, W. R., Cox, M. J., and Family Life Project Key Investigators. (2014). ‘Family violence and children’s behaviour problems: Independent contributions of intimate partner and child-directed physical aggression’. Journal of Family Violence, 29: 773–781. Hawley, P. H. and Vaughn, B. E. (2003). ‘Aggression and adaptive functioning: The bright side to bad behaviour’. Merrill-Palmer Quarterly, 49: 239–242. 16

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Hirschfield, P. J. and Gasper, J. (2011). ‘The relationship between school engagement and delinquency in late childhood and early adolescence’. Journal of Youth and Adolescence, 40: 3–22. Hoffman, M. L. (2001). ‘Toward a comprehensive empathy-based theory of prosocial moral development’. In A. C. Bohart and D. J. Stipek (Eds), Constructive and Destructive Behaviour: Implications for Family, School, and Society. Washington, DC: American Psychological Association, pp. 61–86. Hoffmann, J. P., Erickson, L. D., and Spence, K. R. (2013). ‘Modeling the association between academic achievement and delinquency: An application of interactional theory’. Criminology, 51: 629–660. Hymel, S., Rocke-Henderson, N., and Bonanno, R. A. (2005). ‘Moral disengagement: A framework for understanding bullying among adolescents’. Journal of Social Sciences, 8: 1–11. Jouriles, E. N., Vu, N. L., McDonald, R., and Rosenfield, D. (2014). ‘Children’s appraisals of conflict, beliefs about aggression, and externalizing problems in families characterized by severe intimate partner violence’. Journal of Family Psychology, 28: 915–924. Kazdin, A. E. (1997). ‘Parent management training: Evidence, outcomes, and issues’. Journal of the American Academy of Child & Adolescent Psychiatry, 36: 1349–1356. Kochanska, G., Kim, S., Boldt, L. J., and Yoon, J. E. (2013). ‘Children’s callous-unemotional traits moderate links between their positive relationships with parents at preschool age and externalizing behaviour problems at early school age’. Journal of Child Psychology and Psychiatry, 54: 1251–1260. Kuperminc, G. P., Leadbeater, B. J., and Blatt, S. J. (2001). ‘School social climate and individual differences in vulnerability to psychopathology among middle school students’. Journal of School Psychology, 39: 141–159. Lewis, M. D., Granic, I., Lamm, C., Zelazo, P. D., Stieben, J., Todd, R., Moadab, I., and Pepler, D. (2008). ‘Changes in the neural bases of emotion regulation associated with clinical improvement in children with behaviour problems’. Development and Psychopathology, 20: 913–939. Liu, H., Li, Y., and Guo, G. (2014). ‘Gene by social-environment interaction for youth delinquency and violence: Thirty-nine aggression-related genes’. Social Forces: A Scientific Medium of Social Study and Interpretation, 93: 881. Loeber, R. and Hay, D. (1997). ‘Key issues in the development of aggression and violence from childhood to early adulthood’. Annual Review of Psychology, 48: 371–410. Lösel, F. and Farrington, D. P. (2012). ‘Direct protective and buffering protective factors in the development of youth violence’. American Journal of Preventive Medicine, 43: S8–S23. McKinnon, J. A. (2008). An Unchanged Mind: The Problem of Immaturity in Adolescence. Herndon, VA: Lantern Books. Meldrum, R. C., Connolly, G. M., Flexon, J., and Guerette, R. T. (2016). ‘Parental low self-control, family environments, and juvenile delinquency’. International Journal of Offender Therapy and Comparative Criminology, 60: 1623–1644. Meloni, M. (2014). ‘The social brain meets the reactive genome: Neuroscience, epigenetics and the new social biology’. Frontiers in Human Neuroscience, 8: 309. Menesini, E., Sanchez, V., Fonzi, A., Ortega, R., Costabile, A., and Lo Feudo, G. (2003). ‘Moral emotions and bullying: A cross-national comparison of differences between bullies, victims and outsiders’. Aggressive Behavior, 29: 515–530. Mercer, S. H. and DeRosier, M. E. (2008). ‘Teacher preference, peer rejection, and student aggression: A prospective study of transactional influence and independent contributions to emotional adjustment and grades’. Journal of School Psychology, 46: 661–685. Moore, T. E., and Pepler, D. J. (2006). ‘Wounding words: Maternal verbal aggression and children’s adjustment’. Journal of Family Violence, 21: 89–93. Moretti, M. M. and Obsuth, I. (2009). ‘Effectiveness of an attachment-focused manualized intervention for parents of teens at risk for aggressive behaviour: The Connect Program’. Journal of Adolescence, 32: 1347–1357. Moretti, M. M. and Obsuth, I. (2013). ‘A brief attachment focused treatment program for parents and caregivers’. In D. Pepler and B. Ferguson (Eds), A Focus on Relationships: Understanding and Addressing Girls’ Aggressive Behaviour Problems. Kitchener, ON: Wilfred Laurier Press, pp. 159–180. National Scientific Council on the Developing Child. (2004). ‘Young people develop in an environment of relationships: Working paper no. 1’. Retrieved on January 1, 2012 from www.developingchild.net Naumova, O. Y., Hein, S., Suderman, M., Barbot, B., Lee, M., Raefski, M. L., Raefski, A., Dobrynin, P., Brown, P., Szyf, M., Luthar, S., and Grigorenko, E. L. (2016). ‘Epigenetic patterns modulate the connection between developmental dynamics of parenting and offspring psychosocial adjustment’. Child Development, 87: 98–110. 17

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Nolte, D. L. (1972). ‘Children learn what they live’. Retrieved on April 20, 2017 from www.empowerment resources.com/info2/childrenlearn-long_version.html O’Connell, P., Pepler, D., and Craig, W. (1999). ‘Peer involvement in bullying: Issues and challenges for intervention’. Journal of Adolescence, 22: 437–452. Patterson, G. R. (1982). Coercive Family Process (Vol. 3). Castalia Publishing Company. Pepler, D. (2006). ‘Bullying interventions: A binocular perspective’. Journal of the Canadian Academy of Child and Adolescent Psychiatry, 15: 16–20. Pepler, D. and Slaby, R. (1994). ‘A developmental perspective on violence and youth’. In L. Eron (Ed.), Reason to Hope: A Psychosocial Perspective on Violence and Youth. Washington, DC: APA Publications, pp. 27–58. Pepler, D., Craig, W., Cummings, J., Petrunka, K., and Garwood, S. (in press). ‘Mobilizing Canada to promote healthy relationships and prevent bullying among children and youth’. In P. Sturmey (Ed.), The Wiley Handbook of Violence and Aggression (Vol. 3): Societal Interventions. Pepler, D. J., Craig, W. M., and Roberts, W. L. (1998). ‘Observations of aggressive and nonaggressive children on the school playground’. Merrill-Palmer Quarterly, 44: 55–76. Pepler, D., Jiang, D., Craig, W., and Connolly, J. (2008). ‘Developmental trajectories of bullying and associated factors’. Child Development, 79: 325–338. Pepler, D., King, G., and Byrd, W. (1991). ‘A social-cognitively based social skills training program for aggressive children’. In D. Pepler and K. Rubin (Eds), The Development and Treatment of Childhood Aggression. Hillsdale, NJ: Erlbaum, pp. 361–379. Smith, J. D., Dishion, T. J., Shaw, D. S., and Wilson, M. N. (2015). ‘Negative relational schemas predict the trajectory of coercive dynamics during early childhood’. Journal of Abnormal Child Psychology, 43: 693–703. Speltz, M. L., DeKlyen, M., and Greenberg, M. T. (1999). ‘Attachment in boys with early onset conduct problems’. Development and Psychopathology, 11: 269–285. Sprott, J. B. (2004). ‘The development of early delinquency: Can classroom and school climates make a difference?’ Canadian Journal of Criminology and Criminal Justice, 46: 553–572. Sprott, J. B., Jenkins, J. M., and Doob, A. N. (2005). ‘The importance of school protecting at-risk youth from early offending’. Youth Violence and Juvenile Justice, 3: 59–77. Trentacosta, C. J. and Shaw, D. S. (2008). ‘Maternal predictors of rejecting parenting and early adolescent antisocial behaviour’. Journal of Abnormal Child Psychology, 36: 247. Vitaro, F., Barker, E. D., Boivin, M., Brendgen, M., and Tremblay, R. E. (2006). ‘Do early difficult temperament and harsh parenting differentially predict reactive and proactive aggression?’ Journal of Abnormal Child Psychology, 34: 681–691. Volk, A. A., Camilleri, J. A., Dane, A. V., and Marini, Z. A. (2012). ‘Is adolescent bullying an evolutionary adaptation?’ Aggressive Behavior, 38: 222–238. Wang, M. T. and Fredricks, J. A. (2014). ‘The reciprocal links between school engagement, youth problem behaviors, and school dropout during adolescence’. Child Development, 85: 722–737. Webster-Stratton, C., Jamila Reid, M., and Stoolmiller, M. (2008). ‘Preventing conduct problems and improving school readiness: Evaluation of the Incredible Years teacher and child training programs in high-risk schools’. Journal of Child Psychology and Psychiatry, 49: 471–488. Zadeh, Z. Y., Jenkins, J., and Pepler, D. (2010). ‘A transactional analysis of maternal negativity and child externalizing behaviour’. International Journal of Behavioural Development, 34: 218–228.

18

2 Sex differences in aggression Kaj Björkqvist and Karin Österman

Traditionally, men and boys have been regarded to be more aggressive than women and girls. This is supported by the fact that in most animal species, males are more aggressive than females. There are, however, exceptions to this rule: for example, female lemurs (Kappeler, 1990) and spotted hyenas (Goymann, East, & Hofer, 2001) are more aggressive than their male counterparts. Some decades ago, the view also among researchers in the field was that aggression basically was a male phenomenon. Buss (1961) claimed that women are so seldom aggressive that female aggression was unworthy of academic attention. Olweus (1978), in his pioneering research on school bullying, was of the opinion that bullying appears so rarely among female adolescents that he excluded girls altogether as subjects from his study. Later he changed his opinion, and started to investigate bullying behaviour among girls, too (Olweus, 1986). Frodi, Macaulay, and Thome (1977) reviewed 314 studies on human aggression, and found that 54 per cent of these concerned men only, while only 8 per cent focused on women. Maccoby and Jacklin (1974), in another review, considered it self-evident that males are more aggressive than females. Reviews from the 1980s (Eagly & Steffen, 1986; Hyde, 1984) were more cautious, and while they agreed that males were physically more aggressive than females, they saw sex differences in aggression to be a question of quality rather than quantity. Hyde (1984) suggested that only 5 per cent of variation sources in aggression scores may be explained by sex, while 95 per cent is to be explained as within-sex variation or coincidence. Reviews from the 1990s finally challenged the notion about the non-aggressive human female (Björkqvist, 1994; Björkqvist & Niemelä, 1992). They pointed out the fact that laboratory studies clearly showed that, when not in danger of being recognised, hence being retaliated against, females behaved as aggressively as males (Grusec, 1972; Mallick & McCandless, 1966). They also suggested that research to date had an overemphasis on physical aggression, while other forms, most notably indirect aggression, which might be a more typical form of female aggression, had been overlooked.

Indirect aggression In 1988, Lagerspetz, Björkqvist and Peltonen published a study with the title “Is indirect aggression typical of females?” It was followed in 1992 by another one “Do girls manipulate and 19

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boys fight?” (Björkqvist, Lagerspetz, & Kaukiainen, 1992a). Lagerspetz, Björkqvist and colleagues felt the notion about the non-aggressive female to be incorrect. They interviewed adolescent girls about their behaviour when in conflict with other girls, in which dramatic narratives about conflicts, deception, malicious gossip, back-biting, and bitching were reported. On the basis of these interviews, they constructed a new instrument for the measurement of adolescent aggressive behaviour, with the intent to catch female forms of aggression better – a less gender biased instrument than previous ones. This was to become the Direct & Indirect Aggression Scales (DIAS) (Björkqvist, Lagerspetz, & Österman, 1992b). DIAS was based on peer estimations of aggressive behaviour. Since aggression is a kind of behaviour usually not accepted by social norms, self-reports are less reliable than peer-reports. There are basically two types of peer reports: peer nominations and peer estimations. The rationale of a peer nomination technique is that all pupils in a class are asked to write down the names of those class mates who behave aggressively when in conflict with others. In that way, respondents provide dichotomous responses (aggressive: yes/no) for all pupils in the class, and the yes-responses are added together to a summed aggression score. This method was used by, for instance, Olweus (1978, 1986) and Huesmann and Eron (1986). A peer estimation technique is based on a Likert scale, providing more nuanced data. In the final version of DIAS (Björkqvist et al., 1992b), every pupil in the class estimates the behaviour of every other pupil on a five-point scale (0−4) on a total of 24 items for the measurement of perpetration of aggression, and on another 24 items for victimisation from aggression. In this way, peer estimations of behaviour are obtained as well as separate boys’ estimations and girls’ estimations, which makes sense, since aggressive behaviour in a school class occurs predominantly between individuals from the same sex (Lagerspetz & Björkqvist, 1994). Same-sex estimations are therefore the most reliable source of information on aggressive behaviour in a school class. In addition, DIAS provides self-estimated data, making it possible to compare peer- with self-estimations. After factor-analysing their data, Lagerspetz et al. (1988) found three factors representing three different styles of aggressive behaviour: physical aggression, direct verbal aggression, and indirect aggression. Almost all items with strong loadings in the factor of indirect aggression described some kind of social manipulation: using others as a means for attack instead of attacking oneself, or otherwise manipulating the social network of the school class in order to lower the victim’s standing in the social hierarchy or perhaps even excluding her altogether from a friendship group. Indirect aggression was thus seen as social manipulation with the intention to harm another individual psychologically and/or socially, often attacking the target person circuitously, for example through malicious gossip. Indirect aggression exposes the perpetrator to less risk of retaliation, since, in the best-case scenario, she might be able to stay completely unidentified. Furthermore, indirect aggression makes it easy to deny any aggressive intent; sometimes the perpetrator might not admit even to herself that she is aggressive. For example, slander may be rationalised as “telling the truth” about the individual victim in question. Lagerspetz et al. (1988) found that 15-year-old Finnish girls used indirect aggression significantly more than Finnish boys of the same age. Björkqvist et al. (1992a) extended the age range of their respondents to three age groups: 8-, 11-, and 15-year-old children. They found no sex difference in regard to indirect aggression at the age of 8, but clear differences at ages 11 and 15. Österman, Björkqvist and their colleagues set out to investigate whether the sex difference regarding indirect aggression they had found was a specifically Finnish phenomenon, or if it could be found in other cultures as well. They conducted a cross-cultural study with adolescents from the same three age groups (8, 11, and 15 years old) and four countries: besides Finland, Israel, Italy, and Poland were included. The results are summarised in Figure 2.1, in which verbal aggression was used roughly equally by both sexes. While boys used more physical aggression 20

Girls 8 years

Boys 8years

Verbal 32%

Physical 34%

Verbal 38%

Indirect 34%

Indirect 26%

Girls 11 years

Physical 27%

Boys 1 1 years

Verbal 39%

Indirect 34%

Indirect 27%

Girls 15 years

Verbal 41% Physical 11%

Boys 15 years

Physical 32% Verbal 43%

Indirect 48%

Indirect 25%

Figure 2.1 Proportions of victimisation from physical, verbal, and indirect aggression. Peer-estimated data of girls (n = 1,025) and boys (n = 1,069), of three age groups from Finland, Israel, Italy, and Poland, obtained with the Direct & Indirect Aggression Scales (DIAS). Modified from Österman et al., 1998

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than girls did, girls used more indirect aggression than boys did. At the age of 15, there was a clear increase in indirect aggression and a decrease in physical aggression for girls (Österman, Björkqvist, Lagerspetz, Kaukiainen, Landau, Fraczek, & Caprara, 1998). In summary, a female preference for indirect aggression was cross-culturally corroborated, at least for these countries.

Indirect aggression and related concepts Indirect aggression was introduced as a concept by Buss (1961). However, judging from the items of the subscale of indirect aggression in the Hostility-Guilt Inventory by Buss and Durkee (1957), his understanding of the concept was very different from the one by Lagerspetz, Björkqvist, and colleagues, who saw it as a form of social manipulation. The Buss and Durkee subscale of indirect aggression included items like “slamming doors”, “banging on tables”, “throwing things”, “breaking things”, and “having temper tantrums”. These types of behaviour could be better described as emotional outbreaks and signs of lost self-control rather than as indirect aggression as conceptualised by Lagerspetz et al. (1988) and Björkqvist et al. (1992a). Feshbach (1969) was the first to report a sex difference in indirect aggression with an operationalisation reminiscent of the one by Lagerspetz, Björkqvist, and colleagues. She found that young school girls excluded newcomers from a group to a greater extent than boys did, during the first four minutes of interaction. Her study was well ahead of time; further research on the topic was not conducted until almost 20 years later, when Lagerspetz et al. (1988) published their first study. However, soon competing concepts emerged: Cairns, Cairns, Neckerman, Ferguson, and Gariepy (1989) introduced the concept of social aggression as a description for more or less the same phenomenon as indirect aggression, and some researchers (Galen & Underwood, 1997) started using their concept. To further complicate the situation, Crick and Grotpeter (1995) introduced a third concept, relational aggression. There can hardly be any doubt that all three terms refer to the same phenomenon, creating a confusing situation within the literature. Underwood, Galen, and Paquette (2001) wrote an article with the subtitle, “Why can’t we all just get along?” expressing the need to clarify the concept of indirect/social/relational aggression. In a response to their article, Björkqvist (2001) wrote that there can be no question about the fact that indirect aggression was the first term published; it was a well-established concept prior to the introduction of relational aggression and social aggression. There had been many publications on indirect aggression before Crick and Grotpeter (1995) published their first study on relational aggression, and it is simply impossible that they could have been unaware of them. Björkqvist (2001, p. 272) wrote: “It can hardly be doubted that her (Crick’s) work was strongly inspired by ours, although she does not cite us as a source.” Björkqvist (2001) further pointed out that all types of aggression are by necessity social. Also, physical aggression is a social phenomenon. The same criticism may be directed against the concept of relational aggression. Aggression implies a conflict between at least two people or parties, and, thus, it always concerns social relations. There was no need to invent new labels, since there already existed an established one. In the present chapter, we have accordingly chosen to stick to the term “indirect aggression”. However, we acknowledge the fact that other terms are being used, and most likely will continue to be used as well, in the future research literature.

Developmental trends and the Effect/Danger Ratio Björkqvist, Österman, and Kaukiainen (1992) suggested that physical, verbal, and indirect aggression could be conceived of not only as three different strategies of aggression, but also as 22

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three different stages in human development, partly following, partly overlapping each other. The first stage is physical aggression. Small children who do not yet have a language simply are not able to be verbally aggressive. In that sense, they are like members of subhuman species who have to resort to physical aggression. The first type of aggressive behaviour to appear is most likely biting; the second most likely scratching. Biting requires that the first tooth has appeared, and scratching requires nails. The third one is likely to be pinching, which requires the ability to have two fingers interacting with each other. At nine months old a child should be able to use these three types of aggressive behaviour. Hitting and pushing are more advanced, and they require that the young child be able to stand and walk, that is, the child should be at least around one year of age. Pushing is likely to appear slightly prior to hitting. Kicking is still more advanced, since the child has to be able to keep the balance standing on one leg only; that is, it should be around two years of age. Boys, who are more active than girls, and also often physically stronger, are likely to develop physical means of aggression to a greater degree, through positive conditioning. The second stage is verbal aggression. When verbal skills develop, they facilitate a rich number of possibilities for the expression of aggression without having to resort to physical force. Verbally aggressive strategies are effective, and they put the individual into less danger, since there is no physical contact. Verbal aggression is also more socially accepted than physical, since there is less risk for injury. Accordingly, verbal aggression tends to replace physical more and more, the older the child gets. The third stage, indirect aggression, requires that a certain amount of social intelligence has developed. The child has to be able to analyse social situations in order to manipulate them. Österman et al. (1998) found that 8-year-old children were well able to be indirectly aggressive (cf. Figure 2.1), but girls at the age of 15 used indirect strategies to a much higher degree than younger girls. Vaillancourt, Brendgen, Boivin, and Tremblay (2003) found that children at the age of four were already able to be indirectly aggressive. However, this finding was based on reports by their mothers; still, it should not be surprising that children at a quite early age may already be manipulative. Whether indirect aggression appears also among subhuman species is unclear. There is evidence that chimpanzees are able to deceive in order to attain goals (Hare, Call, & Tomasello, 2006), and that they have some kind of theory-of-mind (Call & Tomasello, 2008; Premack & Woodruff, 1978). Whether they are able to deceive in order to hurt others, i.e. be aggressive, remains to be shown. Björkqvist (1994) suggested that sex differences and developmental trends in regard to aggressive behaviour may both be explained by what he referred to as the Effect/Danger Ratio, a variation of the cost/benefit ratio. This ratio is an expression of the subjective estimation of the likely consequences of an aggressive act. The aggressor assesses the relation between (a) the effect of the intended strategy, and (b) the danger involved, physical, psychological, or social. The objective is to find a technique that will be effective and at the same time incur as little danger as possible. The aggressor tries to maximise the effect and minimise the risks involved. Physical aggression may be effective, but also risky. If unsuccessful, the perpetrator is likely to get hurt. Verbal aggression may have a more favourable ratio, and indirect aggression a still better one. The more the aggressor is able to stay out of reach of the opponent, the better the ratio. Indirect aggression may be highly effective and, in some cases, the aggressor might succeed in staying altogether unidentified. The Effect/Danger Ratio explains how physical strategies are substituted with less risky ones. However, it also explains how male and female aggression have different trajectories. Since males are physically stronger, physical aggression pays better for them in achieving their goals. Females, 23

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who are physically weaker, have to find other means to get even. These strategies are then individually conditioned and culturally strengthened. Other possible contributing reasons for females’ preferential use of indirect aggression are that they are socially more intelligent than males and that they mature faster socially (Cohn, 1991). They also are better able than males to decode and encode nonverbal signals (Hall, 1978, 1990; Hyde, 1990).

Indirect aggression and social intelligence The theory about the development of aggressive strategies suggests a correlation between indirect aggression and social intelligence. We set out to test this hypothesis. The concept of social intelligence was investigated already by Thorndike (1936). However, he was not able to verify the existence of such a domain. It was not until the 1980s that evidence for its existence was found (Cantor & Kihlstrom, 1989; Ford & Tisak, 1983). A problem with tests of social intelligence is that they tend to confound social intelligence with empathy, and see empathy as one part of it (Ford & Tisak, 1983). Furthermore, empathy is known to inhibit or at least mitigate aggressive behaviour (Feshbach, 1989; Miller & Eisenberg, 1988). Accordingly, to test the hypothesis, new measures had to be constructed in which social intelligence and empathy were separated from each other. Since DIAS was based on peer estimation, our research group decided to base the new measures on peer estimations, too. It was hypothesised that indirect aggression should correlate with social intelligence, but that this correlation would increase if empathy was controlled for. This hypothesis was corroborated (Björkqvist, Österman, & Kaukiainen, 2000; Kaukiainen, Björkqvist, Lagerspetz, Österman, Salmivalli, Rothberg, & Ahlbom, 1999). Table 2.1 presents both regular bivariate correlations and partial correlations (with empathy controlled for) between social intelligence and physical, verbal, and indirect aggression, plus peaceful conflict resolution and withdrawal. As the table shows, social intelligence correlated highest with peaceful conflict resolution, as could be expected. However, among the aggressive strategies, it had its highest correlation with indirect aggression, the second highest with verbal aggression, and the weakest with physical aggression. It is noteworthy that all of these were significantly positive; accordingly, some social intelligence seems to be required for all forms of aggression. Turning to the partial correlations controlling for empathy: when empathy scores were partialled out, correlations with all types of aggressive behaviour increased; the correlation with Table 2.1 Bivariate and partial correlations (controlling for empathy) between peer-estimated social intelligence and different types of peer-estimated conflict behaviour (n = 203) Social intelligence

Indirect aggression Verbal aggression Physical aggression Peaceful conflict resolution Withdrawal Source: Modified from Björkqvist et al. (2000). ** p < .01, *** p < .001

24

Bivariate correlations

Partial correlations (empathy controlled)

.55 *** .39 *** .22 ** .80 *** .48 ***

.65 *** .54 *** .38 *** .51 *** .23 ***

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indirect aggression, which already had been high (.55) increased to .65. In the same vein, the correlation between social intelligence and peaceful conflict resolution decreased from .80 to .51. The hypothesis was thus corroborated, and there really seems to be a strong link between indirect aggression and social intelligence. As far as sex differences are concerned, it is worth noting that females in general seem to be better at both social intelligence (Cohn, 1991) and empathy (Eisenberg & Lennon, 1983).

Genetic and evolutionary aspects of indirect aggression One may ask whether there is a genetic component to indirect aggression, or whether it is a behaviour primarily shaped by learning. As far as direct forms of aggression are concerned, about 50 per cent is explained by genetic factors and 50 per cent by environmental factors, in both males and females (Tuvblad & Baker, 2011). According to Tackett, Waldman, and Lahey (2009), a clear genetic component may also be found in indirect aggression, although its strength varies according to whether this form of aggression is measured by self-reports or parental reports. (Tacket et al. did not include studies based on peer reports, which should have been most reliable.) In self-reported data, the genetic component explained 49 per cent of the variance; in parental reports (which are likely to be less reliable), it explained 42 per cent in the case of boys and 21 per cent in the case of girls. If there is a genetic component to indirect aggression, which seems to be the case, it follows that this form of aggression must have an evolutionary advantage. Vaillancourt, Miller, and Sharma (2010) link it directly to female within-sex competition over quality males. Similar analyses have been made by Archer (2010), Baumeister and Twenge (2002), and Geary (1998). Vaillancourt et al. (2010) refer in their analysis to Trivers’ (1972) Differential Parental Investment Theory. According to Trivers, females across species, including humans, invest more resources in their offspring than do males. Due to this investment imbalance, they are choosier about their sexual partners than males. They want to select a partner from as high up in the social hierarchy as possible; females are more selective, while males are more contending. Vaillancourt et al. (2010) argue that the competition between reproductive females is fierce, and that they use indirect aggression at an alarming rate in this competition. Among 1,100 university students, they found that only 5.8 per cent reported not having talked behind another person’s back during the last 12 months; only 10.6 per cent had never used sarcasm to insult others; only 12.9 per cent had never been “bitchy” towards others, and only 16.7 per cent had never intentionally ignored another. Accordingly, the vast majority admitted the use of indirectly aggressive strategies.

Sex differences in intimate partner aggression So far, we have examined mainly same-sex aggression in adolescent peer groups and in sexual competition between adult women. Aggressive behaviour in intimate partnerships is qualitatively different from aggressive behaviour in same-sex groups. The aggression taking place in intimate partner relationships is most commonly between individuals of the opposite sex, and it is all about social dominance in a dyad, it is not related to social hierarchy in a larger group. Although intimate partner aggression (IPA) is considered in detail in other sections of this volume, a few words need to be said about the phenomenon in the present chapter as well since it concerns sex differences in aggression. As Archer (2000) points out, there are two quite conflicting viewpoints about IPA. One sees it mainly as a male problem; males are the aggressors, and their female partners are more or less innocent victims. This viewpoint is represented especially, but not exclusively, by feminist 25

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writers like Dobash and Dobash (1980), Pagelow (1984), and Walker (1989). Typically, they view IPA primarily as wife battering, and they use specific terminology like the word “patriarchy”. However, some evolutionary psychologists advocate for this view as well (for example, Smuts, 1992, 1995), arguing that the patriarchy arose from male attempts to control the reproductive choices of females. According to the other viewpoint, IPA consists most typically of mutual combat between partners, where male and female spouses fight each other more or less equally successfully with a number of different physical and nonphysical strategies. The best-known representative for this viewpoint is Straus (e.g. Straus, 1979, 1999; Straus & Gelles, 1992). Straus (1997), based on national survey data from the US, found that females actually used physical violence more often than their male partners. Similar findings have been made by others (see the review by Archer (2000) and his Chapter 13 in this volume). However, Dobash, Dobash, Wilson, and Daly (1992), who advocate the feminist viewpoint, argued that the methods used by family interaction researchers, like Straus’ (1979) Conflict Tactics Scale, yield biased results. If the consequences of physical violence are considered – homicide and injuries – then most victims are clearly women. It has been pointed out that proponents of the two viewpoints tend to collect their data by different sampling procedures (Johnson, 1995). Feminist researchers typically study samples selected for high levels of IPA to begin with, such as women from refuges, or violent men on treatment programmes. Family interaction researchers, on the other hand, base their findings on more representative community data of married, cohabiting, or dating couples. According to Johnson (1995), these two types of samples represent non-overlapping populations. There is something to both of these viewpoints. If we examine “normal”, average couples, there does not appear to be any sex difference in regard to IPA; if anything, women spouses behave aggressively more frequently than men. Alternatively, if we look at outcomes in terms of severity of injuries, including homicide, then men are more aggressive (Daly & Wilson, 1988). A point worth noting is that there is considerable cultural variation in sex differences in spousal homicide. In the US, women kill their husbands more frequently than in other countries: the proportion of male to female homicide victims is 44:56 (Wilson & Daly, 1992). This is clearly higher than in other cultures. Wilson and Daly argue that this must be due to some factors specific to the US; we suggest that the most likely reason is the easy access to guns.

The testosterone–aggression link A link between testosterone and aggression is well established among subhuman species (Benton, 1992). However, the closer the animal is to man, the smaller the influence of testosterone on aggression (Björkqvist, 1994). Archer (1991) conducted three meta-analyses and found a weak, positive relationship between testosterone and human aggression. Book, Starzyk, and Quinsey (2001) made a meta-analysis based on 45 independent studies, and found correlations ranging from r = –.28 to r = .71; that is, a very large variation. The mean weighted correlation was .14, which according to Book et al. corroborates Archer’s finding of a weak, but positive relationship. Book et al. (2001) point out several problems in studies of the testosterone–aggression link. First, testosterone levels fluctuate daily and seasonally. Individual levels are highest and most variable in the morning, while they are lower and more stable in the afternoon. Since they are highest in the morning, researchers usually collect saliva or blood samples in the morning. This practice is problematic, precisely since the morning levels are more variable than during other times of the day. Age is another issue: the level of testosterone varies during the lifespan (Mazur & Booth, 1998). It increases rapidly in males during puberty, and it is high among young adults, but 26

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decreases around middle age (Julian & McKenry, 1989). This pattern correlates with physically aggressive behaviour in males. Daly and Wilson (1994) refers to this as the “Young Male Syndrome”, and points out that males between the ages of 12 and 25 are the principal perpetrators (and victims) of physical violence. This finding suggests that testosterone is involved in withinsex competition among males. Testosterone levels are also affected by winning and losing, they increase when you win, and decrease when you lose. This fact has been observed in sports like wrestling and tennis (Elias, 1981), but also in chess (Mazur, Booth, & Dabbs Jr., 1992). Testosterone levels also rise prior to competition, as if in anticipation of the coming conflict (Mazur & Booth, 1998). Thus, the central evolutionary function of testosterone appears to be that it is related to male competition about reproductive females, and that females are attracted to winners. Otherwise, a selection for this relationship would not have taken place. If mating success is the primary adaptive value of the positive relationship between testosterone and aggression, mated status would be expected to moderate this relationship (Book et al., 2001). Support for this hypothesis was established by Booth and Dabbs Jr. (1993), who found that testosterone levels fall and remain lower when a man gets married, but rises if he divorces. This rise is likely to occur because he again is mentally prepared to compete for females.

Conclusion In this chapter, sex differences in aggressive behaviour have been described. Overall, it can be concluded that aggressive behaviour in groups is qualitatively different from aggressive behaviour in intimate partnerships. In groups, aggression is for the most part a within-sex phenomenon: males are aggressive towards other males, and females towards other females, although exceptions to this rule naturally occur (Lagerspetz & Björkqvist, 1994). If we consider the choice of aggressive strategies, males and females use verbal aggression equally often in proportion of the total aggressive behaviour they display. However, males use physical aggression to a greater proportion than females, while females use indirect aggression to a greater proportion than males (Österman et al., 1998). Turning to opposite-sex dyads and more specifically to intimate partner aggression, studies based on representative community data indicate that males and females in relationships tend to be aggressive roughly to the same extent (Straus, 1997). However, due to the difference in physical strength, injuries, both fatal and nonfatal, are more common among female victims (Daly & Wilson, 1988). The question of which is the “more aggressive sex” is meaningless without a clarification about what is meant by “more” and “less”. When not in danger of being recognised, hence being retaliated against, females behave exactly as aggressively as males (Grusec, 1972; Mallick & McCandless, 1966). If we look at frequency of aggressive encounters, regardless of type and outcome, there does not appear to be any sex difference. However, if we consider the severity of physical injuries and the number of homicides, then males clearly are more aggressive.

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Baumeister, R. F. and Twenge, J. M. (2002). ‘Cultural suppression of female sexuality.’ Review of General Psychology, 8: 111−121. Benton, D. (1992). ‘Hormones and human aggression.’ In: K. Björkqvist and P. Niemelä, eds. Of Mice and Women: Aspects of Female Aggression. San Diego, CA: Academic Press, pp. 37−48. Björkqvist, K. (1994). ‘Sex differences in physical, verbal, and indirect aggression: A review of recent research.’ Sex Roles, 30: 177−188. Björkqvist, K. (2001). ‘Different names, same issue.’ Social Development, 10: 272–274. Björkqvist, K. and Niemelä, P. (1992). ‘New trends in the study of female aggression.’ In: K. Björkqvist and P. Niemelä, eds. Of Mice and Women: Aspects of Female Aggression. San Diego, CA: Academic Press, pp. 3−16. Björkqvist, K., Lagerspetz, K. M. J., and Kaukiainen, A. (1992a). ‘Do girls manipulate and boys fight? Developmental trends in regard to direct and indirect aggression.’ Aggressive Behaviour, 18: 117–127. Björkqvist, K., Lagerspetz, K. M. J., and Österman, K. (1992b). The Direct & Indirect Aggression Scales. Vasa, Finland: Åbo Akademi University. Björkqvist, K., Österman, K., and Kaukiainen, A. (1992). ‘The development of direct and indirect aggressive strategies in males and females.’ In: K. Björkqvist and P. Niemelä, eds. Of Mice and Women: Aspects of Female Aggression. San Diego, CA: Academic Press, pp. 51–64. Björkqvist, K., Österman, K., and Kaukiainen, A. (2000). ‘Social intelligence – empathy = aggression?’ Aggression and Violent Behaviour, 5: 191–200. Björkqvist, K., Österman, K., and Lagerspetz, K. M. J. (1994). ‘Sex differences in covert aggression among adults.’ Aggressive Behaviour, 20: 27–33. Book, A. S., Starzyk, K. B., and Quinsey, V. L. (2001). ‘The relationship between testosterone and aggression: A meta-analysis.’ Aggression and Violent Behaviour, 6: 579−599. Booth, A. and Dabbs Jr., J. M. (1993). ‘Testosterone and men’s marriages.’ Social Forces, 72: 463−477. Buss, A. H. (1961). The Psychology of Aggression. New York: Wiley. Buss, A. H. and Durkee, A. (1957). ‘An inventory for assessing different types of hostility.’ Journal of Consulting Psychology, 21: 343−349. Cairns, R. B., Cairns, B. D., Neckerman, H. J., Ferguson, L. L., and Gariepy, J. (1989). ‘Growth and aggression: 1. Childhood to early adolescence.’ Developmental Psychology, 25: 320−330. Call, J. and Tomasello, M. (2008). ‘Does the chimpanzee have a theory of mind? 30 years later.’ Trends in Cognitive Sciences, 12: 187−192. Cantor, N. and Kihlstrom, J. F. (1989). ‘Social intelligence and cognitive assessments of personality.’ In: R. S. Wyer, Jr. and T. K. Srull, eds. Social Intelligence and Cognitive Assessment of Personality: Advances in Social Cognition (Vol. 2). Hillsdale, NJ: Lawrence Erlbaum, pp. 1−59. Cohn, L. D. (1991). ‘Sex differences in the course of personality development: A meta-analysis.’ Psychological Bulletin, 109: 252−266. Crick, N. R. and Grotpeter, J. K. (1995). ‘Relational aggression, gender, and socio-psychological adjustment.’ Child Development, 66: 710−722. Daly, M. and Wilson, M. (1988). Homicide. New York: Aldine de Gruyter. Daly, M. and Wilson, M. (1994). ‘Evolutionary psychology of male violence.’ In: J. Archer, ed. Male Violence. New York: Routledge, pp. 253−288. Dobash, R. E. and Dobash, R. P. (1980). Violence Against Wives: A Case Against the Patriarchy. London: Open Books. Dobash, R. P., Dobash, R. E., Wilson, M., and Daly, M. (1992). ‘The myth of sexual symmetry in marital violence.’ Social Problems, 39: 71−91. Eagly, A. H. and Steffen, V. J. (1986). ‘Gender and aggressive behaviour: A meta-analytic review of the social psychological literature.’ Psychological Bulletin, 100: 309−330. Eisenberg, N. and Lennon, R. (1983). ‘Sex differences in empathy and related capacities.’ Psychological Bulletin, 94: 100−131. Elias, M. (1981). ‘Serum cortisol, testosterone, and testosterone binding globulin responses to competitive fighting in human males.’ Aggressive Behaviour, 7: 215−224. Feshbach, N. D. (1969). ‘Sex differences in children’s modes of aggressive responses toward outsiders.’ Merrill Palmer Quarterly, 15: 249−258. Feshbach, N. D. (1989). ‘Empathy training and prosocial behaviour.’ In: J. Groebel and R. A. Hinde, eds. Aggression and War: Their Biological and Social Bases. Cambridge, UK: Cambridge University Press, pp. 101−111. 28

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Ford, M. E. and Tisak, M. S. (1983). ‘A further search for social intelligence.’ Journal of Educational Psychology, 75: 196−206. Frodi, A., Macaulay, J., and Thome, P. R. (1977). ‘Are women always less aggressive than men?’ Psychological Bulletin, 84: 634−660. Galen, B. R. and Underwood, M. K. (1997). ‘A developmental investigation of social aggression among children.’ Developmental Psychology, 33: 589−600. Geary, D. C. (1998). Male, Female: The Evolution of Human Sex Differences. Washington, DC: American Psychological Association. Goymann, W., East, M. L., and Hofer, H. (2001). ‘Androgens and the role of female hyperaggressiveness in spotted hyenas (Crocuta crocuta).’ Hormones and Behaviour, 39: 83−92. Grusec, J. E. (1972). ‘Demand characteristics of the modeling experiment: Altruism as a function of sex and aggression.’ Journal of Personality and Social Psychology, 22: 139−148. Hall, J. A. (1978). ‘Gender effects in decoding nonverbal cues.’ Psychological Bulletin, 85: 845−857. Hall, J. A. (1990). Nonverbal Sex Differences: Accuracy of Communication and Expressive Style. Baltimore, MD: Johns Hopkins University Press. Hare, B., Call, J., and Tomasello, M. (2006). ‘Chimpanzees deceive a human competitor by hiding.’ Cognition, 101: 495−514. Huesmann, L. E. and Eron, L. D. (1986). Television and the Aggressive Child: A Cross-national Comparison. Hillsdale, NJ: Lawrence Erlbaum. Hyde, J. S. (1984). ‘How large are gender differences in aggression? A developmental meta-analysis.’ Developmental Psychology, 20: 722−736. Hyde, J. S. (1990). ‘Meta-analysis and the psychology of sex differences.’ Signs, 16: 55−73. Johnson, M. P. (1995). ‘Patriarchal terrorism and common couple violence: Two forms of violence against women.’ Journal of Marriage and the Family, 57: 283−294. Julian, T. and McKenry, P. (1989). ‘Relationship of testosterone to men’s family functioning at mid-life: A research note.’ Aggressive Behaviour, 15: 281−289. Kappeler, P. M. (1990). ‘Female dominance in Lemur catta: More than just feeding priority?’ Folia Primatology, 55: 92−103. Kaukiainen, A., Björkqvist, K., Lagerspetz, K. M. J., Österman, K., Salmivalli, E. C., Rothberg, S., and Ahlbom, A. (1999). ‘The relationships between social intelligence, empathy, and three types of aggression.’ Aggressive Behaviour, 25: 81–89. Lagerspetz, K. M. J. and Björkqvist, K. (1994). ‘Indirect aggression in girls and boys.’ In: L. R. Huesmann, ed. Aggressive Behaviour: Current Perspectives. New York: Plenum, pp. 131–150. Lagerspetz, K. M. J., Björkqvist, K., and Peltonen, T. (1988). ‘Is indirect aggression typical of females? Gender differences in aggressiveness in 11- to 12-year-old children.’ Aggressive Behaviour, 14: 403–414. Maccoby, E. E. and Jacklin, C. N. (1974). The Psychology of Sex Differences. Palo Alto, CA: Stanford University Press. Mallick, S. K. and McCandless, B. R. (1966). ‘A study of catharsis of aggression.’ Journal of Personality and Social Psychology, 4: 591−596. Mazur, A. and Booth, A. (1998). ‘Testosterone and dominance in men.’ Behavioural and Brain Sciences, 21: 353−397. Mazur, A., Booth, A., and Dabbs Jr., J. M. (1992). ‘Testosterone and chess competition.’ Social Psychology Quarterly, 55: 70−77. Miller, P. A. and Eisenberg, N. (1988). The relationship of empathy to aggressive and externalizing/ antisocial behaviour. Psychological Bulletin, 103: 324−344. Olweus, D. (1978). Aggression in the Schools: Bullies and Whipping Boys. New York: Wiley. Olweus, D. (1986). Mobbning. Stockholm, Sweden: Liber. Österman, K., Björkqvist, K., Lagerspetz, K. M. J., Kaukiainen, A., Landau, S. F., Fraczek, A., and Caprara, G.-V. (1998). ‘Cross-cultural evidence of female indirect aggression.’ Aggressive Behaviour, 24: 1–8. Pagelow, M. D. (1984). Family Violence. New York: Praeger. Premack, D. and Woodruff, G. (1978). ‘Does the chimpanzee have a theory of mind?’ Behavioural and Brain Sciences, 1: 515−526. Smuts, B. (1992). ‘Male aggression against women: An evolutionary perspective.’ Human Nature, 3: 1−44. Smuts, B. (1995). ‘The evolutionary origins of patriarchy.’ Human Nature, 6: 1−32. Straus, M. A. (1979). ‘Measuring intrafamily conflict and violence: The Conflict Tactics (CT) Scales.’ Journal of Marriage and the Family, 41: 75−88. 29

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Straus, M. A. (1997). ‘Physical assaults by women partners: A major social problem.’ In: M. R. Walsh, ed. Women, Men and Gender: Ongoing Debates. New Haven, CT: Yale University Press, pp. 210−221. Straus, M. A. (1999). ‘The controversy over domestic violence by women: A methodological, theoretical, and sociology of science analysis.’ In: X. B. Arriaga and S. Oskamp, eds. Violence in Intimate Relationships. Thousand Oaks, CA: SAGE, pp. 17−44. Straus, M. A. and Gelles, R. J., eds. (1992). Physical Violence in American Societies: Risk Factors and Adaptations to Violence in 8,145 Families. New Brunswick, NJ: Transaction Publications. Tackett, J. L., Waldman, I. D., and Lahey, B. B. (2009). ‘Etiology and measurement of relational aggression: A multi-informant behaviour genetic investigation.’ Journal of Abnormal Psychology, 118: 722−733. Thorndike, E. L. (1936). ‘Factor analysis of social and abstract intelligence.’ Journal of Educational Psychology, 27: 231−233. Trivers, R. L. (1972). ‘Parental investment and sexual selection.’ In: B. Campbell, ed. Sexual Selection and the Descent of Man. Chicago, IL: Aldine, pp. 136−179. Tuvblad, C. and Baker, L. A. (2011). ‘Human aggression across the lifespan: Genetic propensities and environmental moderators.’ Advances in Genetics, 75: 171−214. Underwood, M. K., Galen, B. R., and Paquette, J. A. (2001). ‘Top ten challenges for understanding gender and aggression in children: Why can’t we all just get along?’ Social Development, 10: 248−266. Vaillancourt, T., Brendgen, M., Boivin, M., and Tremblay, R. (2003). ‘Longitudinal confirmatory factor analysis of indirect and physical aggression: Evidence of two factors over time?’ Child Development, 74: 1628−1638. Vaillancourt, T., Miller, J. M., and Sharma, A. (2010). ‘“Tripping the prom queen”: Female intrasexual competition and indirect aggression.’ In: K. Österman, ed. Indirect and Direct Aggression. Frankfurt am Main, Germany: Peter Lang, pp. 17−31. Walker, L. E. A. (1989). ‘Psychology and violence against women.’ American Psychologist, 44: 659−702. Wilson, M. and Daly, M. (1992). ‘Who kills whom in spouse killing? On the exceptional sex ratio of spousal homicides in the United States.’ Criminology, 30: 189−215.

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3 Hegemonic masculinity and aggression Ruschelle M. Leone and Dominic J. Parrott1

When you durst do it, then you were a man/And, to be more than what you were, you would/Be so much more than a man William Shakespeare, Macbeth (1.7.49–51)

These are the words of Lady Macbeth, who viewed her husband as masculine when he dared to murder the king and assume the throne, yet emasculates him when he expresses his unwillingness to commit the murder. Masculinity and violence have long been connected in both literary and scientific writing. Extant scientific literature suggests that men are more aggressive than women (Bettencourt & Miller, 1996; Eagly & Steffen, 1986; Knight, Guthrie, Page & Fabes, 2002). However, it is important to note that these differences are complex. For example, when considering aggression that is used without the intention of physical harm such as indirect or relational aggression, women’s rates of aggressive behaviour have been shown to exceed men’s (for a review, see Archer & Coyne, 2005). In particular, while a considerable amount of research has examined the effects of biological sex on aggression (for a review, see Archer, 2004), scholars have more recently begun to consider how gender and social roles contribute to aggression. Contemporary scholars have consistently argued that hegemonic masculinity, which refers to a pattern of social practices perpetuating men’s dominance over women (Connell & Messerschmidt, 2005), may be more predictive of aggression than one’s biological sex (Richardson & Hammock, 2007). For instance, a meta-analysis of 39 studies found robust support for the relation between masculine ideology and men’s perpetration of sexual aggression toward women (Murnen, Wright & Kaluzny, 2002). As such, a growing emphasis has been placed on how masculine cultural and socialisation pressures are related to aggressive behaviour. The aim of this chapter is to critically review theoretical and empirical evidence that seeks to explain how hegemonic masculinity contributes to, and is a result of, men’s perpetration of aggression. Conclusions from this review will be used to suggest directions for future research and strategies for intervention.

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Definitions and theoretical overview Defining masculinity Masculinity refers to the social and cultural roles, personality traits, and behaviours that are deemed socially acceptable for men (Mosher & Tomkins, 1988). Masculinity has numerous conceptualisations that encompass a variety of qualities, including attitudes, values, cognitions, emotions, and behaviours (e.g., Thompson & Pleck, 1995; Thompson & Bennett, 2015). Various terms are utilised in the literature to refer to masculinity including, but not limited to: manhood, masculine ideology, hypermasculinity, hegemonic masculinity, traditional masculinity, gender roles, gender role identity, gender role strain, gender role stress, gender role orientation, and sex role. While many of these terms are used interchangeably, scholars have called for the use of definitions with greater conceptual clarity to promote conceptual distinctions between constructs (e.g., Thompson & Bennett, 2015; Cuthbert, 2015). Despite myriad conceptualisations and definitions of masculinity, research has consistently demonstrated that measures of masculinity based on sexist masculine role norms are robustly associated with aggression. As such, the present chapter will focus on hegemonic masculinity, which refers to: the configuration of gender practice which embodies the currently accepted answer to the problem of the legitimacy of patriarchy, which guarantees (or is taken to guarantee) the dominant position of men and the subordination of women. Connell, 2005, p. 77 Hegemonic masculinity essentialises male-female differences as well as the division among men by marginalising men of colour, lower social class, and a non-heterosexual identity (Carrigan, Connell & Lee, 1985; Connell, 2005). Further, hegemonic masculinity is not a fixed, transhistorical model, but rather masculinities are configurations of practice that are fluid and may unfold and change across time (Connell & Messerschmidt, 2005). Men can adopt hegemonic masculinity when it is desirable or necessary in certain contexts and distance themselves strategically in other contexts. Importantly, hegemonic masculinity is not monolithic, but rather multiple “masculinities” and facets of those masculinities exist (for a review, see Connell, 2005).

Theoretical conceptualisations of masculinity Prior to reviewing research that links hegemonic masculinity and aggression, it is first important to discuss pertinent masculinity theory. Scholars have utilised multiple approaches to examine hegemonic masculinity; however, three approaches have been the most widely used: (1) gender orientation, (2) gender normative, and (3) masculine gender stress.

Gender orientation perspective The gender orientation approach is one of the earliest conceptualisations of masculinity and posits that masculinity is comprised of socially desirable, ingrained personality traits or attributes that differentiate males and females (Connell & Messerschmidt, 2005; Thompson & Pleck, 1995). In other words, masculinity exists as a “configuration of fixed individual attributes” (Luyt, 2005, p. 6) that exemplifies the idealised man. Although this approach has historically dominated the field, there has been a paradigm shift in the last 20 years toward a conceptualisation that emphasises societally based hegemonic norms (Thompson & Bennett, 2015). Given this shift, 32

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the present chapter will not review literature that links trait masculinity and aggression. We note, however, that the evidence supporting this link is equivocal (for a review, see Moore & Stuart, 2005). Instead, we review two contemporary approaches that examine (1) the gender normative perspective and (2) the masculine gender stress perspective.

Gender normative perspective The gender normative perspective purports that masculinity is “a culturally based ideology scripting gender relations, attitudes, and beliefs” (Thompson & Pleck, 1995, p. 30). From this approach, masculinity is considered a set of external cultural or social standards that is a function of a particular time or place. In contrast to the gender orientation approach, which examines the extent to which hegemonic masculinity is incorporated into one’s self-description (e.g., I am dominant), the gender normative conceptualisation examines men’s beliefs about how they should behave, feel, or act in gender-salient situations (e.g., Men should be dominant). In other words, the gender orientation approach examines men’s internalisation of hegemonic masculinity whereas the gender normative approach examines men’s endorsement of hegemonic masculinity. The most influential conceptualisation of masculinity utilising this approach was put forward by Brannon (1976), who explored the American cultural “blueprint” of what a man should be, desire, and accomplish. He theorised that there were four core themes, or standards, of the masculine gender role: No Sissy Stuff (i.e., avoiding femininity, concealing emotions), the Big Wheel (i.e., being the breadwinner, being admired and respected), the Sturdy Oak (i.e., being tough, confident, and self-reliant); and Give ’em Hell (i.e., willingness to engage in violence and adventure). Thompson and Pleck (1986) advanced this conceptualisation by analysing the empirical structure of male role norms via a factor analysis of Brannon’s scale of masculine ideology. They found that men varied in their adherence to three distinct male role norms: (a) status (i.e., the Big Wheel), which reflects the belief that men must gain the respect of others, (b) toughness (i.e., the Sturdy Oak and Give ’em Hell), which reflects the expectation that men are physically tough and willing to be aggressive, and (c) antifemininity (i.e., No Sissy Stuff ), which reflects the belief that men should not engage in stereotypical feminine activities. More recently, Mahalik and colleagues (2003) argued that this three-factor conceptualisation of masculinity is too narrow and posited the inclusion of affective (e.g., feeling proud or happy when conforming to masculine role norms), behavioural (i.e., acting in ways to meet societal expectations for men), and cognitive dimensions (i.e., holding beliefs expected of men) of the male gender role. A factor analysis evidenced 11 theoretically driven masculine norms assessing affective, behavioural, and cognitive domains to which men can conform: emotional control, risk-taking, violence, dominance, playboy, winning, primacy of work, power over women, self-reliance, disdain for homosexuals, and pursuit of status (Mahalik et al., 2003).

Masculine gender stress perspective The gender normative approach predominately focuses on men’s endorsement of hegemonic masculinity; however, research has also focused on men who are unable to conform or live up to standards of hegemonic masculinity. Given the rigid standards of hegemonic masculinity, the proportion of men who violate gender norms is undoubtedly high due to the inconsistent and frequent changes in what is considered “masculine” behaviour (Pleck, 1995). As such, men may experience psychological and physiological stress (i.e., masculine gender stress) when failing to live up to the hegemonic manhood ideal (Eisler & Skidmore, 1987; Eisler, Skidmore & Ward, 1988). Although gender stress is related to beliefs about masculinity, masculine gender stress is a 33

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unique construct that focuses on men’s gendered or masculine experience and the degree to which men cognitively appraise gender-relevant situations (e.g., being subordinate to a woman, failing at work or sex) as stressful or threatening (Walker, Tokar & Fischer, 2000).

Theoretical explanations of the link between hegemonic masculinity and aggression Hegemonic masculinity as a cause Aggressive behaviour may result from gender role socialisation that teaches hegemonic norms promoting aggression. In line with the gender normative perspective, how men should behave, feel, or act in gender-salient situations influences their behaviour in those situations. In accordance with social learning theory (Bandura, 1973), from an early age boys observe socially acceptable behaviour from parents, teachers, peers, and the media about “masculine” behaviour. These behaviours are learned through reinforcement (e.g., praise for winning) and punishment (e.g., criticism for showing emotion) by others (Pleck, 1981, 1995). Moreover, males are socialised to conform to a narrow definition of masculinity often summarised by dimensions such as breadwinning, stoicism, independence, dominance, avoiding intimacy, and approval of violence (Levant et al., 2007; Mahalik et al., 2003; Smiler, 2004). Men may vary within and across these aforementioned dimensions of masculinity; however, men are defined, and learn to define themselves, by what they are (e.g., dominant, heterosexual), as well as what they are not (e.g., submissive, homosexual; Brannon, 1976; Pleck, 1981). Masculine socialisation and endorsement of cultural masculine standards may produce a restriction of vulnerable emotions (e.g., Levant, 1996; Levant et al., 2007). To this end, anger is one of the few emotions viewed as acceptable for men to express, especially during periods of distress (Lisak, Hopper & Song, 1996; Moore & Stuart, 2004). It is well established that hostile affect contributes to the expression of aggression (Anderson & Bushman, 2002), and thus the social acceptance and expectation of men’s anger likely contributes to aggressive behaviour. Further, theorists postulate a major characterisation of masculinity as a willingness to engage in aggressive behaviour if necessary (e.g., Brannon, 1976; Levant et al., 2007). Male aggression is viewed as normative in many cultures (Mahalik et al., 2003), and male-perpetrated aggression is often a by-product of socialisation and cultural pressures to adhere to a hegemonic masculinity (O’Neil et al., 1986; Pleck, 1995).

Hegemonic masculinity as a consequence Aggression may also be a tactic used to demonstrate hegemonic masculinity (Messerschmidt, 1997). Indeed, aggression may serve various functions, including harming a victim and reestablishing one’s self-image (see Anderson & Bushman, 2002). In line with this view, aggression is a way for men to achieve and bolster masculinity, particularly when experiencing masculine gender stress. Traditional gender roles uphold power differences between men and women by conceptualising men as dominant, aggressive, and at the top of the social hierarchy, and women as submissive, nurturing, and at the bottom of the social hierarchy (Levant, 1996). As such, men may perpetrate aggression to maintain or re-establish this dominant position and achieve hegemonic masculine status. Consistent with this view, impression management theory (Felson, 1978) postulates that aggression is most likely expressed when the perpetrator’s concerns about his identity are salient and onlookers are supportive of aggressive behaviour. Men who feel their masculinity is in question may behave aggressively around others who will provide 34

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reinforcement with social and “manly” approval. More broadly, men may engage in aggressive behaviour in private settings (e.g., against a partner) and later be reinforced when bragging to their friends.

Empirical evidence linking hegemonic masculinity and aggression Gender normative perspective Research has consistently demonstrated that endorsement of hegemonic norms is positively associated with self-reported intimate partner psychological aggression (Good, Heppner, Hillenbrand-Gunn & Wang, 1995), severity of men’s symbolic aggression (e.g., insults, smashing things), and frequency and severity of psychological aggression in intimate relationships (Jenkins & Aubé, 2002). A similar pattern of effects exists using a related conceptualisation of hegemonic masculinity that assesses affective, behavioural, and cognitive dimensions of masculine norms (Mahalik et al., 2003). Specifically, research has demonstrated that hegemonic norms are strongly and positively correlated with self-reported general aggression (Mahalik et al., 2003), intimate partner aggression (Tager, Good & Brammer, 2010), and laboratorybased physical aggression (Berke, Sloan, Parrott & Zeichner, 2012; Reidy, Sloan & Zeichner, 2009) among college men. The majority of research examining hegemonic norms and aggression has used a multidimensional approach to consider how facets of masculinity may uniquely predict different forms of aggression. For instance, studies indicate that only adherence to the toughness norm, but not status or antifemininity norms, predicts self-reported intimate partner physical aggression (Lisco, Leone, Gallagher & Parrott, 2015) and self-reported aggression towards a gay male (Vincent, Parrott & Peterson, 2011). Additionally, using both self-report and laboratory-based measures of aggression, research indicates that adherence to the status and antifemininity norms indirectly facilitates aggression toward gay, but not heterosexual, men via sexual prejudice (Parrott, 2009; Parrott, Peterson & Bakeman, 2011; Vincent et al., 2011) and right-wing authoritarianism (Goodnight, Cook, Parrott & Peterson, 2014). Further, hegemonic norms about power over women, playboy, dominance, and disdain for gay men are strong predictors of college men’s self-reported sexual aggression, whereas norms reflecting risk-taking and violence were only modest predictors (Locke & Mahalik, 2005). The aforementioned research is consistent with the view that men’s demonstration of different hegemonic masculine norms is context dependent (Connell, 2005). In other words, it may be that men’s beliefs regarding “masculine” behaviour are especially salient in some contexts (e.g., around gay men) and dormant in others (e.g., around children). Although research directly examining context-dependent masculinity is limited, sociological research suggests that expectations of masculine behaviour vary across contexts. Indeed, men are expected to adhere to non-hegemonic “nice guy” masculinities in romantic and family situations, but should adhere to more traditional norms in work and social environments (Talbot & Quayle, 2010). Moreover, there is evidence that certain contextual factors such as men’s acute alcohol intoxication (Leone & Parrott, 2015) and perception of women’s female gender norm conformity (Berke et al., 2012) alter the hegemonic norm-aggression link.

Masculine gender stress perspective Empirical evidence has consistently demonstrated an association between masculine gender stress and self-reported and laboratory-based aggression against women in college and community 35

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samples (for review, see Moore & Stuart, 2005). For example, masculine gender stress independently predicts sexual aggression (e.g., Malamuth et al., 1995; Zurbriggen, 2010) and intimate partner aggression (e.g., Eisler et al., 2000; Franchina, Eisler & Moore, 2001) and interacts with men’s adherence to masculine ideologies (Jakupcak, Lisak & Roemer, 2002; Jakupcak, 2003) and adult attachment style (Mahalik et al., 2005; McDermott & Lopez, 2013) to predict intimate partner aggression. More recent research has built upon these findings by disentangling specific factors of masculine gender stress that uniquely predict aggression. Moore and colleagues (2010) demonstrated that specific forms of stress impact couple’s conflict in unique ways in a clinical sample of violent men. For example, stress related to failure to perform at work (e.g., being unemployed) or to perform sexually may place a strain on the relationship and cause tension that leads to an increase in psychological and verbal aggression. More recently research indicates that male social drinkers who appraise situations where they are subordinate to their female partners as stressful may be compelled to maintain dominance via sexual aggression (Smith, Parrott, Swartout & Tharp, 2015). Research has also considered how men’s predisposition to appraise gender-relevant situations as stressful may interact with environmental cues to elicit stress. While all men may experience some stress when attempting to meet gender-relevant standards, men high in masculine gender stress may be especially prone to stress following threats to their masculinity, which in turn may facilitate aggression. Research has demonstrated that gender threatening feedback from a female intimate partner was related to significantly more negative attributions, negative affect, and endorsement of verbal aggression in men high, relative to those low, in masculine gender stress (Franchina, Eisler & Moore, 2001). Similarly, experimental research has revealed that men experience anxiety following gender-relevant threats (Vandello et al., 2008), which in turn leads them to take measures to re-establish or demonstrate their masculinity via aggression (Bosson et al., 2009; Cohn, Seibert & Zeichner, 2009). Perhaps this is because manhood is a precarious social status that is difficult to earn and easy to lose (Vandello & Bosson, 2012). Thus, aggression may serve as a way for men to restore their masculinity when threatened.

Limitations of the review and how it can inform research The preceding review suggests that the gender normative and masculine gender stress approaches demonstrate consistent, albeit nuanced, relationships with aggressive behaviour. First, the reviewed research suggests that men may engage in aggression as a way to conform to hegemonic masculine standards. Importantly, this research suggests that specific facets of hegemonic masculinity may directly or indirectly predict forms of aggression depending on the situational context or environmental cues. In other words, what is considered masculine behaviour may vary across contexts (e.g., with peers versus with a partner). Although various theorists argue aggression is a central component of masculinity (e.g., Brannon, 1976; Levant et al., 2007), the empirical literature reviewed in this chapter suggests that other facets of masculinity (e.g., antifemininity) can be stronger predictors of aggression (Parrott, 2009; Parrott, Peterson & Bakeman, 2011; Vincent et al., 2011). The reviewed research also demonstrates how aggression may serve as a psychological salve to the stress some men experience in attempting to conform to hegemonic masculinity. For example, aggression may be used to restore one’s masculinity following anxiety related to being outperformed by a woman. In this regard, aggression serves a function: to bolster one’s masculinity. Moreover, there is some evidence to suggest that specific domains of masculine gender stress perpetuate aggression to the extent that they activate a man’s need to demonstrate 36

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his manhood in a way most likely to restore his masculine status (Bosson et al., 2009; Cohn, Seibert & Zeichner, 2009). Although some research has examined how situational masculinerelevant threats predict physical aggression, more experimental or event-based research is needed to consider how failure to live up to idealised masculine standards may cause stress and facilitate aggression. Further, it is important to understand whether men experience acute gender stress or concerns about their masculine identity when perpetrating aggression. Elucidating the contexts in which men are most likely to demonstrate or restore their masculinity through aggression will help to identify triggers for these men and more accurately inform prevention efforts. Despite the need for additional research on the masculine gender stress approach to explicitly test state-based and contextual facilitators of aggression, this approach has been highly generative in advancing theory and presenting testable hypotheses regarding the impact of social expectations of masculinity on aggression via internalised gender stress. Literature that links hegemonic masculinity to aggression against women is well developed (e.g., Moore & Stuart, 2005); in contrast, the role of masculinity in men’s aggression toward other targets is less well understood and would benefit from greater empirical scrutiny. For example, there have been recent calls for research to examine school- and community-based firearm violence (Davies et al., 2014). Despite the fact that 154 out of 160 active shooters from 2000 to 2013 were male (FBI, 2013), there remains no evidence on the link between hegemonic masculinity and firearm violence. Similarly, the prevalence of child sexual and physical abuse, bullying, male-to-male intimate relationships, workplace or sports aggression, and male-to-male physical aggression has been well documented (e.g., Barling, Dupré & Kelloway, 2009; Finkelhor et al., 2014; Salmivalli et al., 1996; Sønderlund et al., 2014; Stanley et al., 2006); yet, there is a dearth of empirical evidence examining how hegemonic masculinity may contribute to, or result from, such aggression. Another limitation of the extant literature is the need for more research that examines masculinity as a multidimensional, rather than unitary, construct. This is important for several reasons. First, there are a host of cultural beliefs about the male gender role that are both positive and negative in nature (e.g., Brannon, 1976; Thompson & Pleck, 1995); however, research has overwhelmingly focused on how negative masculinity (e.g., men should be tough and aggressive) predicts behaviour. Although it is well documented that men are more likely to perpetrate aggression than women, it is also true that most men are not aggressive (Kilmartin, 2010). It may be that positive masculinity (e.g., men should be respectful of others) may serve as a protective factor for maladaptive behaviours, including aggression. Second, a multidimensional approach allows for a more nuanced understanding of the relation between hegemonic masculinity and aggression that can more accurately inform intervention and prevention efforts by allowing programs to target the most relevant dimensions of masculinity. The literature is also limited because most studies recruit samples that lack racial, ethnic, age, and gender diversity. Despite the advancement of measures that take into account masculinities specific to a particular racial or ethnic group (Thompson & Bennett, 2015), there exists little empirical evidence that examines how diverse masculinities are associated with aggression. Additionally, most measures of masculinity were empirically validated in college-aged samples (e.g., Mahalik et al., 2003) and the extant literature predominately focuses on college men. This is certainly an important population given the high rates of aggression (Archer, 2004); however, future research should strive to understand how these findings may generalise or deviate in other age groups. Finally, it is unclear how women’s endorsement of hegemonic masculine norms may predict aggression perpetration. Scholars have recently validated measures of masculinity among women (Parent & Smiler, 2013), and future research should consider the masculinity–aggression link in women who endorse hegemonic norms. 37

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Intervention and prevention implications Limitations notwithstanding, this body of work has important implications for violence prevention. Despite the strong link between hegemonic masculinity and aggression, there are few empirically validated prevention or intervention efforts which directly target masculinity. At the individual level, clinicians working with aggressive men may benefit from targeting their belief systems regarding masculinity. Exploring and reconstructing the messages men receive about their gender may help mitigate socialisation pressures to adhere to hegemonic masculinity. Similarly, clinicians can collaborate with men to identify other non-aggressive behaviours to bolster or express their masculinity in gender-relevant situations. Among previously violent men, ‘batterer’ intervention programs would benefit from incorporating masculinity into their curriculum to reduce intimate partner violence. For example, the intervention program Men Stopping Violence trains facilitators to openly challenge messages men receive about dominance over women (Douglas, Bathrick & Perry, 2008), though we note this program has yet to be subjected to empirical scrutiny. Given the pervasiveness of expectations about masculine behaviour at the societal level, the most promising interventions are likely those directed at the community or group level. Social norms theory postulates that individuals are negatively influenced by their inaccurate perceptions of how other members of their social group think or act (Berkowitz, 2003; Perkins & Berkowitz, 1986). These misperceptions increase the likelihood that individuals will engage in behaviours that they may otherwise resist if their perceptions were accurate. Research indicates men tend to overestimate the aggressiveness of their male peers and the attractiveness of aggression to women (Vandello, Cohen & Ransom, 2008; Vandello et al., 2009). Thus, social norm interventions that seek to reconstruct the way men view hegemonic masculinity and target misperceptions of peer attitudes about aggression may lead to a decrease in aggression (e.g., Katz, 1995). For example, the web-based sexual violence bystander intervention program, Real Consent (Salazar, Vivolo-Kantor, Hardin & Berkowitz, 2014), targets a range of predictors of sexual violence (e.g., knowledge of informed consent) including adherence to extreme gender-role beliefs. Real Consent participants reported less adherence to extreme gender-role beliefs, less sexual violence perpetration, and more bystander intervention behaviour, compared to controls. However, it remains unclear if these reductions in extreme gender-role beliefs accounted for changes in violence perpetration. While targeting social norms may be effective at the individual level, group formats in which men can collectively discuss the implications of rigid standards of masculinity may be more transformative. These are especially promising because they engage all men, rather than just perpetrators, in violence prevention. Indeed, bystander intervention programs to prevent gender-based violence utilise techniques including social marketing campaigns and structured psychoeducational programs to reconstruct masculine norms that promote violence (e.g., Katz, 1995; Salazar, et al., 2014). For example, the school-based teen dating violence prevention program, Safe Dates (Foshee et al., 2004), includes a component that aims to challenge and decrease adherence to traditional gender norms. Research indicates that this intervention resulted in reduced rates of adolescent dating violence perpetration, and the effect was mediated by changes in gender role norms (Foshee et al., 2005). This study provides important preliminary evidence that interventions targeting hegemonic masculinity can decrease men’s adherence to and endorsement of hegemonic masculine norms and ultimately help reduce aggressive behaviour.

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Conclusion Masculinity and violence have been connected long before Lady Macbeth questioned her husband’s masculinity; however, scholars have only begun to empirically examine how masculine cultural and socialisation pressures are related to aggressive behaviour within the past two decades. The present chapter reviewed theoretical and empirical evidence linking hegemonic masculinity and aggression, utilising the gender normative and the masculine gender stress perspectives to examining masculinity. In sum, theoretical and empirical evidence consistently indicates that hegemonic masculinity contributes to, and is a consequence of, aggressive behaviour. However, the link between hegemonic masculinity and aggression is complex and many fundamental questions remain unanswered. In many ways, this chapter raises more questions than answers and highlights the critical need for more research to examine this link. For example, does the masculinity–aggression link vary across situational contexts? How are different domains of masculinity associated with various forms of aggression? Do extant findings generalise to diverse populations? As the answers to these, and other, questions become more clear, researchers and practitioners will be better able to reduce male-perpetrated aggression.

Note 1 We thank Dr Danielle Berke for her helpful comments on a previous version of this chapter.

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4 The biology of human aggression Tracy A. Bedrosian and Randy J. Nelson

Aggression is a social behaviour expressed during conflict as a means to obtain or defend resources. Virtually all species display some form of aggression, from fruit flies and rodents to humans. When it is expressed in context, aggression is a functional and adaptive behaviour. Protecting and defending oneself, offspring, and resources is crucial to survival and maintenance of any individual’s fitness. In contrast, aggression that is exaggerated or persists out of context may be considered pathological. This latter form of aggression represents a tremendous burden to human society. In 2014, over a million violent crimes were reported in each the United States and England (United States Department of Justice, 2015; United Kingdom Office for National Statistics, 2016), costing billions in government spending (McCollister, French & Fang, 2010). There is an urgent need to understand why some individuals display inappropriate aggression and how to prevent it. In general, human aggression can be divided into two subtypes: controlled-instrumental and reactive-impulsive (Nelson & Trainor, 2007; Vitiello & Stoff, 1997). Controlled-instrumental aggression is deliberate, preconceived behaviour executed as a means to achieve a specific goal. An example would be someone who threatens or attacks another individual to manipulate them into behaving a certain way. In contrast, reactive-impulsive aggression is hostile behaviour occurring in response to anger or frustration. An example would be someone who lashes out in anger in response to provocation. Research using nonhuman animal models has focused heavily on the reactive-impulsive subtype of aggression because it is more easily modelled in laboratory animals. Many species, including flies and rodents, will display impulsive aggression depending on the context. Much of the underlying neural circuitry implicated in these interactions is present in humans, making model organisms1 a valuable tool for understanding human aggression. Current research efforts have provided evidence for genetic, neuroanatomical, biochemical, and hormonal correlates of aggression and violence. Some of this evidence comes from genetic testing and brain imaging of violent individuals or individuals with personality traits linked to aggression, such as impulsivity. Other evidence comes from direct laboratory testing of model organisms. Integrating findings from humans and nonhuman animals has provided an overall picture of the biological basis of aggression. This chapter provides a broad overview of the biology of aggression and discusses how those findings can contribute to a solution for violence in society. 43

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Biological basis of aggression Genetic Humans display extensive individual variations in the propensity toward aggressive behaviour. This variation can result from heritable genetic components, environmental influences, or a combination of both. One way to tease apart the contributions of genes and the environment is by comparing individuals with shared genes or shared environments. A useful experimental paradigm is to compare behavioural traits among monozygotic (identical) vs. dizygotic (fraternal) twins or siblings raised in the same family environment. Another common paradigm is to compare behavioural traits of adoptive siblings, who share a family environment, but no genetic material. From comparisons such as these, it is evident that a relatively large proportion of individual variation in aggression is explained by heritable genetic factors. Meta-analysis of twin and adoption studies estimate 40–50 per cent of the variance in both aggressive and antisocial behaviours is heritable (Miles & Carey, 1997; Rhee & Waldman, 2002). At younger ages, environmental influences still hold weight in predicting aggression, but during adulthood the effect of the family environment decreases and heritability becomes an even more prominent influence (Miles & Carey, 1997). Some of the heritability of aggression can be attributed to specific gene variants. Candidate Gene Association Studies (CGAS) and Genome-Wide Association Studies (GWAS) are methods of analysing whether gene variants, either from an a priori determined set of genes (CGAS) or across the entire genome (GWAS), are associated with a given phenotypic trait. These studies have identified a number of genes putatively associated with trait aggression in humans. CGAS implicates serotonergic, dopaminergic, and hormone-related genes in aggressive behaviour and GWAS identifies neurodevelopmental and plasticity-related genes (reviewed in Veroude et al., 2016). So far sample sizes are small and fairly heterogeneous so the results must be interpreted with caution. However, they point toward roles for both neural transmission and neural plasticity in shaping aggressive tendencies. Gene knockout experiments in rodent models have further narrowed the pool of genes associated with aggression. By experimentally eliminating a gene’s function and then determining the behavioural consequence, researchers have established causal roles for specific genes in aggression. Gene knockout can be either ubiquitous or controlled at temporal and spatial levels using inducible and cell-type specific knockout approaches. Gene knockout experiments using rodents have provided some of the best support to date for the role of specific genes in aggression and have guided studies in humans. Only a few of many genes implicated in aggression and studied using knockout techniques are discussed in detail here. Serotonin (5-hydroxytryptamine or 5-HT) is believed to play a role in many complex behaviours, including aggression and impulsivity, but its effects are mediated through many different receptors, making it difficult to determine which specific pathways are important for aggression. Through targeted knockout experiments, it was discovered that mice lacking the gene for 5HT1B receptor display impulsive aggression in a resident-intruder test (Bouwknecht et al., 2001). In this test, an unfamiliar mouse (the intruder) is placed into the home cage of the experimental mouse (the resident). The interactions of the two mice are videotaped for several minutes and the resident’s behaviour is analysed for signs of threat (e.g., tail rattling) or attack (e.g., biting or boxing). 5HT1B knockout mice engage in more threatening and fighting behaviours than their wild-type counterparts, suggesting serotonin’s role in aggressive behaviour is mediated, at least in part, through the 5HT1B receptor. Subsequent studies in humans revealed 44

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a similar finding. In humans, variants at the A-161T locus of the 5HT1B gene promoter are associated with impulsive-aggressive behaviours, including suicide (Zouk et al., 2007). At least in mice, the impulsivity and aggression appear to be separate phenotypes that are regulated through distinct spatial and temporal expression patterns of 5HT1B receptors (Nautiyal et al., 2015). Tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme for the synthesis of serotonin in the brain. Deletion of the Tph2 gene leads to depletion of brain serotonin. Mice lacking the Tph2 gene exhibit compulsive and impulsive behaviours, as well as intense aggression. Tph2 knockout mice shred three times as much nest material as wild-type mice in a given time and bury more than twice as many marbles in a marble-burying task. They display motor impulsivity, more readily emerging from a safe and dark environment to a brightly lit arena. In the residentintruder task, Tph2 knockout mice attack four times as often as wild-type mice, but administering the serotonin precursor 5-HTP eliminates the aggressive behaviour (Angoa-Perez, 2012). These data suggest that disruption of the Tph2 gene influences aggression by decreasing serotonin levels and inducing impulsivity; studies in humans support this notion. Individuals with the G-703T polymorphism in the Tph2 gene have poor anger control and reduced grey matter concentration in the orbitofrontal cortex (Yoon et al., 2012). Monoamine oxidase A (MAOA) is an enzyme responsible for degrading amine neurotransmitters in the brain, including dopamine, norepinephrine, and serotonin. Mice with a spontaneous point mutation in the Maoa gene exhibit complete MAOA deficiency and impulsive aggression (Scott, Bortolato, Chen & Shih, 2008). The mutation is similar to that found in Brunner syndrome, where the afflicted individual displays highly impulsive and violent behaviour (Brunner et al., 1993). Reduced MAOA activity may affect aggression by creating an imbalance in neurotransmitter levels, despite leading to increased brain serotonin concentrations (Cases et al., 1995). Other gene variants compromising MAOA function result in similar phenotypes. The Variable number tandem repeat (VNTR) 2 repeat in the Maoa gene, which confers low activity compared to other variants, is associated with violent and delinquent behaviour among adolescent and young adult males (Guo et al., 2008). Low activity Maoa variants were also associated with extremely violent, homicidal behaviour among Finnish prisoners (Tiihonen et al., 2015). Genes related to nontraditional neurotransmitters can also play a role in aggression. Nitric oxide is a small diffusible molecule that acts as a cell-to-cell signaller. Male mice lacking the gene encoding neuronal nitric oxide synthase (nNOS or Nos1) exhibit highly aggressive behaviour in a resident-intruder test, as do mice treated with a pharmacological nNOS inhibitor (Nelson et al., 1995; Demas et al., 1997). nNOS catalyses the production of nitric oxide in the brain. In humans, short repeat variants of Nos1 are less transcriptionally active and associated with hyperactive, impulsive, and aggressive behaviours (Retz et al., 2010; Reif et al., 2009). Single nucleotide polymorphisms (SNPs) within the Nos1 gene are associated with self-inflicted violence (i.e., suicidal behaviour), but the functional effect of each SNP on gene activity has not yet been determined (Rujescu et al., 2008).

Neuroanatomical Structural and functional variation of the brain can be an important determinant of aggressive behaviour. Understanding functional relationships between anatomy and behaviour is made more difficult, however, because brain regions that regulate aggression overlap with regions involved in social behaviours. This has made it challenging to delineate a specific aggression 45

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circuit. In rodents, olfactory stimuli are relayed from the olfactory bulbs to a number of brain regions involved in emotional response, including the medial amygdala (MeA), bed nucleus of the stria terminalis (BNST), medial preoptic area (MPOA), lateral septum (LAS), anterior hypothalamus (AHA), ventral medial hypothalamus (VMH), and periaqueductal grey (PAG) (DaVanzo, Sydow & Garris, 1983; Delville, DeFries & Ferris, 2000). In model organisms, brain activation following an aggressive encounter can be examined indirectly using the expression of an immediate early gene, such as c-fos, as a proxy for neuronal activity. Following mating or an aggressive encounter, male hamsters exhibit similar activation of several brain regions, including the MeA and LAS. But hamsters exposed to an aggressive episode have selective activation of the anterolateral BNST, AHA, and dorsal PAG, implicating those regions specifically in aggression versus general social behaviours (Kollack-Walker & Newman, 1995). Ablation and activation studies using animal models have also identified some of the brain regions required for normal aggression. For example, lesions of the LAS, BNST, MeA, and AHA reduce aggressive interactions among male rodents (Kruk, 1991). Alternatively, optogenetic stimulation of the VMH elicits indiscriminate aggression among male mice toward other males, females, and even inanimate objects (Lin et al., 2011). Interestingly, the ventrolateral part of the VMH specifically becomes active in mice seeking an aggressive interaction, suggesting this structure has a role in the motivational aspect of aggression as well as the physical action (Falkner et al., 2016). At a higher level, lesions of the orbitofrontal cortex result in increased aggression among male rats, suggesting there is inhibitory pressure from higher cortical regions that suppresses aggression circuitry (de Bruin, Van Oyen & Van De Poll, 1983). In humans, higher order cortical structures similarly serve to inhibit aggressive impulses. Violent psychiatric patients that underwent positron emission tomography (PET) had low brain glucose metabolism in the prefrontal and medial temporal cortices compared to normal control subjects (Volkow et al., 1995). Also, similar to the findings of rodent studies, amygdala function seems to be important for human aggression. Men with lower amygdalar volume display more aggressive and psychopathic behaviours from childhood through adulthood (Pardini, Raine, Erickson & Loeber, 2014). This may reflect a dysfunction in amygdala response. Individuals diagnosed with intermittent explosive disorder, characterised by reactive aggression, exhibit greater amygdala activation and reduced orbitofrontal cortex activation while viewing images of angry faces (Coccaro, Mccloskey, Fitzgerald & Fann, 2007). Interestingly, some of the functional deficits in brain activation interact with genetic variants previously identified. For example, impulsive aggressive individuals with low-activity Maoa gene variants also have reduced limbic volume, hyperactivation of the amygdala during emotional arousal, and low orbitofrontal cortex activation (Meyer-Lindenberg et al., 2006).

Neurochemical The distinct brain regions that make up the neural circuits of aggression communicate with one another through a variety of neurotransmitters and neuropeptides. Manipulating the levels of these chemical messengers in animal models has revealed their important roles in regulating aggressive behaviour. For one, serotonin has been extensively studied in relation to aggression. Generally, low levels of serotonin are associated with aggressive and impulsive behaviour. Treatments that increase serotonin concentrations generally decrease aggression across a number of species (Simon & Lu, 2005). In rodents, aggression is reduced by treatment with 5-HT precursors, selective serotonin reuptake inhibitors (SSRIs), and 5HT1A and 5HT1B receptor agonists (Manuck, Kaplan & Lotrich, 2006). Humans who score higher on a scale of lifetime 46

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aggression have lower 5HT1A binding in the orbitofrontal cortex, measured by PET scans after treatment with a radiolabeled receptor antagonist (Parsey et al., 2002). These results support the conclusion that serotonergic activity is negatively correlated with aggression. Mesocorticolimbic dopamine neurons contribute to various motivated behaviours, including aggression, mating, and food and drug intake. Mice treated with dopamine receptor antagonists consistently display heightened aggression (de Almeida, Ferrari, Parmigiani & Miczek, 2005). Interestingly, dopamine seems to mediate a rewarding component of confrontation in aggressive male rats. Aggressive rats that were exposed to an opponent daily for ten days showed signs of anticipation. Real time in vivo brain microdialysis was used to analyse dopamine and serotonin concentrations in the nucleus accumbens. In the hour before the scheduled encounter, the rats experienced increased heart rate, 60–70 per cent increases in dopamine levels, and 30–35 per cent decreases in serotonin (Ferrari, Van Erp, Tornatzky & Miczek, 2003). Similar changes in monoamine levels could be observed up to an hour following an aggressive encounter (Van Erp & Miczek, 2000). Furthermore, aggressive Swiss-Webster mice will repeatedly poke a sensor to gain access to a confrontation, but not after infusing dopamine antagonists into the nucleus accumbens (Couppis & Kennedy, 2008). In humans, antipsychotic drugs that block dopamine receptors are known to reduce aggressive and psychotic behaviour in some patients, underscoring the importance of dopamine transmission in regulating aggression. Gamma-Aminobutyric acid (GABA) is the brain’s primary inhibitory neurotransmitter and it has been shown to play a role in forebrain-mediated inhibition of aggression. In rodents, aggressive behaviour tends to be inhibited by pharmacological treatments that increase GABA concentrations (Miczek, Fish & De Bold, 2003). In humans, benzodiazepines and barbiturates, which are allosteric modulators of the GABAA receptor, can increase or decrease aggression depending on the dose (Miczek, Fish, De Bold & De Almeida, 2002). One prominent example is alcohol, which escalates aggression in some individuals at moderate doses, but is sedative at higher doses. It appears that GABAA receptor subunit composition determines its sensitivity to modulators and its effect on behaviour (Rudolph et al., 1999).

Hormonal Steroid hormones have both organisational and activational effects on adult behaviours. During early development, they permanently organise the nervous system in a sex-specific fashion. In adulthood, they activate or inhibit male or female typical behaviours. In some species, male aggressive behaviour increases around the time of puberty, when testosterone concentrations rise. Androgens are thought to promote aggressive behaviour, but findings from humans are mixed. In many rodent species, testosterone concentrations rise in the summer and aggressive behaviour increases at the same time that males must compete for mates. In humans, testosterone concentrations tend to increase in response to competition (Mazur & Lamb, 1980; Booth et al., 1989). Even watching a sporting match can induce a significant increase in salivary testosterone concentrations if the fan’s favourite team is winning (Bernhardt, Dabbs, Fielden & Lutter, 1998). But the effects of testosterone on human aggression are less clear. Numerous studies have investigated this relationship but there is tremendous individual variability in baseline testosterone levels that make results difficult to interpret. Also, there seem to be many modulating factors for the effect of testosterone on aggression. For example, among male offenders, high testosterone concentrations are associated with more violent crimes, but only among individuals with low cortisol concentrations (Dabbs, Jurkovic & Frady, 1991). Similarly, exogenous testosterone can 47

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rapidly induce aggression in some men, but only those with dominant or impulsive personalities (Carre et al., 2016). Furthermore, steroid hormones are capable of interacting with other systems involved in the regulation of aggressive behaviour. The human Maoa promoter contains glucocorticoid/androgen response elements, through which glucocorticoid and androgen receptors can interact to upregulate Maoa gene expression (Ou, Chen & Shih, 2006).

Environmental interactions Though biological factors may predispose an individual to aggression, environmental factors exert an important influence in modulating the behaviour. For one, biology contributes to an individual’s behaviour in response to a particular environmental context. Conversely, persistent environmental factors can affect an individual’s biology and behaviour. For instance, different strains of inbred laboratory mice with different genetic backgrounds have varying levels of aggression (Scott, 1942). Their specific genetic background determines how they behave in a residentintruder test of aggression. But mice belonging to the least aggressive strain will become more aggressive if they repeatedly win fights, and highly aggressive strains of mice will become less aggressive if subjected to chronic social defeat (Ginsburg & Allee, 1942). Environmental context modulates the intrinsic behavioural tendency. As another example, male Siberian hamsters undergo seasonal changes in physiology and behaviour. In short day lengths, the hamsters exhibit a marked reduction in the number of nNOS-immunoreactive cells in the amygdala and paraventricular nucleus of the hypothalamus, which is accompanied by a pronounced increase in aggressive behaviour (Wen, Hotchkiss, Demas & Nelson, 2004). Levels of nNOS are implicated in the short-day aggression because blocking it in long days enhances aggressive behaviour (Bedrosian, Fonken, Demas & Nelson, 2012). Several complex interactions between biology and behaviour have been observed in humans as well.

Maltreatment Childhood maltreatment is a risk factor for criminality and antisocial behaviour, including hostility and violence. Variants of the Maoa gene appear to mediate susceptibility versus resilience in this context. Male victims of childhood maltreatment who carry a low-activity allele are more susceptible to developing antisocial tendencies, including violent offending (Caspi et al., 2002). The particular Maoa variant does not affect the risk of antisocial behaviour in children without maltreatment. Many studies have examined this gene–environment interaction and confirmed on average the interaction between low MAOA activity and antisocial behaviour following exposure to maltreatment (Byrd & Manuck, 2014; Kim-Cohen et al., 2006). Genetic variation of Tph1 and the serotonin transporter are also associated with more antisocial tendencies in response to childhood maltreatment (Cicchetti, Rogosch & Thibodeau, 2012). In these examples, the behavioural outcome of early-life adversity is strongly influenced by the underlying biology of the individual.

Stress Situational stress can influence the probability that an individual will become aggressive, but often individuals with certain personality traits or underlying biology are the most likely to be affected. In a model where the subject controls the shocks given to another individual, subjects exposed to aversive air blasts delivered shocks faster. Those individuals rated as having 48

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trait-negative emotionality delivered the most intense shocks, suggesting intrinsic personality characteristics interacted with environmental stress to affect the level of aggression (Verona, Patrick & Lang, 2002). But to fully understand how biology and environment interact to drive aggressive behaviour, it will be necessary to pinpoint specific genes and systems involved. Using a similar model, men, but not women, with a homozygous short allele genotype (s/s) for the serotonin transporter gene showed more aggression under stress by delivering more shocks, whereas men and women carrying the long allele were unaffected by stress (Verona, Joiner, Johnson & Bender, 2006).

Conclusions and ethical implications One objective of biological research on aggression is to determine why humans commit violent crime and how to prevent or treat aggression in society. But identifying biological correlates of aggression has ethical and judicial implications. To what extent is an individual responsible for biologically predisposed behaviours? In one striking case report, a 40-year-old man without prior criminal history developed a sudden interest in child pornography and made advances at his young stepdaughter. He was committed to an inpatient treatment facility and obtained a neurologic consultation after complaining of headaches and balance problems. The doctors discovered a large brain mass displacing the orbitofrontal lobe. After resection of the tumor, the man remarkably regained his normal personality and returned home. Months later, he began collecting child pornography once again and was re-examined by doctors. The tumor had regrown. After re-resecting the mass, his behaviour returned to normal again (Burns & Swerdlow, 2003). In this case, there was a clear biological correlate of the pedophilic behaviour, leading to the question of whether or not he should be held responsible for his behaviour. Interestingly, doctors reported that the man knew his behaviour was unacceptable because he went to lengths to cover it up, suggesting he did in fact have some sense of accountability. In certain criminal cases, biological evidence has been presented as proof that the offender was predisposed to commit violent acts or otherwise lacked appropriate impulse control and moral decision-making capabilities. This raises interesting questions about how courts should treat such evidence, how strong the underlying research findings must be, and how to weigh responsibility and punishment (Glenn & Raine, 2014). Further, if biological factors can predict violent offending or offer treatment, then is it ethical to screen individuals or mandate treatments? In 1963, Spanish researcher José Delgado drew attention to these issues with his famous bullfighting experiment. Delgado had devoted his career to studying how electrical stimulation of the brain controls animal behaviour and emotional responses. In his most famous experiment, Delgado stepped into a ring with a highly aggressive bull that began to charge him. Moments before it could strike him, Delgado pushed a button on an electrical transmitter and the bull stopped in its tracks and quietly trotted away. The bull had an electrical stimulator implanted into the caudate nucleus of its brain and the signal instantly diffused its aggressive reaction. The experiment elicited outrage from the public and the scientific community because it raised fears that human behaviour could be controlled using electrodes. Nevertheless, in subsequent decades the field of neuromodulation advanced rapidly and deep brain stimulation is now an FDA-approved treatment for Parkinson’s disease and depression (Zheng, 2011). The efficacy of neuromodulation in treating these diseases reignites early ethical debates sparked by Delgado’s work. Is neuromodulation an ethical treatment for violent offenders? Current alternatives, which amount to life in prison or a death sentence, do not seem ideal. And if biomarkers that predict violent tendencies could be identified, should individuals 49

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be implanted preemptively with biofeedback sensors to prevent any expression of the undesirable behaviour? Biological research on aggression will need to be carefully considered before integrating any findings into the current justice system. But in the meantime, aggression research holds promise in devising treatments for uncontrolled aggression in the clinic and for unraveling the environmental components that affect the development of aggression. Understanding these environmental and biological correlates of aggression may ultimately reduce violence in society.

Note 1 A model organism is a non-human species that possesses some biological similarities to humans, making it useful for studying biological phenomena relevant to human health and disease. Particularly in cases where studying humans directly has been unfeasible or unethical, experiments using model organisms have led to important biological insights that were later translated into important breakthroughs for both human and animal health.

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5 Aggression motivation and inhibition Theoretical underpinnings and a new model Ioan Ohlsson

Human aggression remains subject to extensive exploration and theoretical reflection. Historical explanations for aggression have shifted from single factors (i.e. poor affect regulation; Berkowitz, 1993), to more current integrated theoretical models covering multiple factors (Megargee, 2011). Despite this, conceptual debates and differences remain due to varying interpretations as to the nature of aggression, how it is displayed and its function(s) (Krahe, 2013). Intent is emphasised as a fundamental consideration in differentiating aggression from nonaggression (Baron & Richardson, 1994; Geen, 2001; Ireland, 2011). The concept of underlying motivation is therefore embedded within current definitional considerations of aggression. It remains important in understanding the decision to aggress by representing the core objectives and intentions of the aggressor. Ireland (2011) argues that the continued difficulties in establishing a universally accepted definition must influence a shift to considering both the form and motivations of aggressive behaviour. The study of motivation is concerned with addressing why a particular movement or action is initiated, persists over time, or is inhibited, and the choices made as part of such processes (Mook, 1987; Weiner, 1992). A number of alternative terms, such as underlying intentions, desires, or functions (Matson, Tureck, & Rieske, 2012), are used in the literature and yet all have comparable meanings. In terms of aggression inhibition, Averill (1983) was one of the first scholars to acknowledge that most individuals experience inclinations towards aggressive behaviour, yet they do not act on these owing to some inhibitory force. Berkowitz (1990) later added that tendencies towards aggression are inhibited due to the operation of a self-regulatory mechanism. Bettencourt et al. (2006) observed that theoretical development and testing of inhibitors for aggression had largely been neglected. Since then an increased interest in the empirical evaluation of aggression inhibition has unfolded. An example of a recent theory that emphasises an equal role for both motivation and inhibition in aggression is Finkel’s (2007) I3 Theory. Pronounced ‘I-cubed theory’ this framework sought to impose greater theoretical coherence on the factors capable of promoting as well as preventing aggression (Denson, DeWall & Finkel, 2012; Finkel & Slotter, 2009). I3 theory identifies three processes as pivotal to determining whether aggressive urges culminate in aggression or instead are overridden in favour of non-aggression. These three factors are the Instigators, Impellors, and Inhibitors with the initial letter of each representing the three I’s 54

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in I3 theory. Preceding models fail to attend to the possibility that urges to aggression are not always acted upon and thus place little or no emphasis on inhibition. There is a return to this notion later in this chapter.

Typologies and known functions of aggression Due to evidence of its relative stability across contexts (see Kempes et al., 2005), some researchers believe that distinct subtypes of aggression are identifiable (Loeber & Hay, 1997). A number of dichotomous distinctions exist in the aggression literature including those that attend to its form and those that consider its function or motivation (Little et al., 2003). The direct versus indirect distinction encapsulated the forms of aggressive behaviour most clearly (Archer, 2001; Ireland & Murray, 2005). Direct aggression involves physical contact with an object or another person and is inclusive of behaviours such as hitting, kicking and pushing. Verbal forms of direct aggression include yelling, making hurtful remarks and threats towards another (Little et al., 2003). Indirect aggression differs as it is based on the actions of the instigator and can include manipulation of a social environment to hurt the target, damaging its self-esteem or social status, using humour hurtfully or damaging interpersonal relationships through exclusion or malice (Ireland, 2011). Alternative terms, such as relational (Little et al., 2003), covert (Bjorkqvist, Osterman & Lagerspetz, 1994), emotional (Bjorkovist, 1992), relational-appearing and social manipulation (Crick & Grotpeter, 1995) are also utilised, yet essentially, they all describe indirect forms of aggression. Separate distinctions exist that consider aggression motivation. Proactive aggression is characterised by planned behaviours generally executed without emotion. Arguably, it is closely related to social-learning models, which maintain that maladaptive behaviours such as aggression are learnt and reinforced over time by perceived or actual rewards (Cima & Raine, 2009). Reactive aggression, however, is characterised as an uncontrolled form of aggression, a largely impulsive response driven by emotion and likely to occur in response to a blocked goal (Berkowitz, 1989; Raine et al., 2006). In recent years the mixed-motive aggressor has been acknowledged, based on the notion that motivation is a fluid concept and that individuals can present with both forms (i.e. reactive and/or proactive) at different times (Gendreau & Archer, 2005). Dodge et al. (1997) among others (i.e. Polman et al., 2007) found that proactive and reactive types were highly correlated. Despite evidence that these motives can coexist (Gendreu & Archer, 2005), several studies neglect the mixed category, focusing on proactive and reactive as two distinct types (Raine et al., 2006). Support for the distinction between proactive and reactive aggressive motivations is provided by several studies in clinical and non-clinical samples of children and adults (Polman et al., 2007; Raine et al., 2006). These subtypes have also been related to distinct developmental experiences and individual profiles (Card & Little, 2006). Advocates of the proactive/reactive dichotomy argue its value lies in operationalising the concept of aggression, permitting more focused empirical and theoretical exploration (Raine et al., 2006). However, Bushman and Anderson (2001) criticised the distinction on the grounds that it confounds different categories of information processing and facilitates confusion over motives for aggression. They recommend that the distinction be abandoned in favour of a structural model for motivation that considers its likely wider and varying dimensions. They argue that reactive and proactive themes are likely to form only a part of any such framework of understanding. Beyond the reactive/proactive distinction, to the authors’ best knowledge few published studies have directly examined or identified the specific motivations for aggression. The available studies (see Table 5.1) are equally limited in respect of their low sample size and generalisability, methodological concerns from experimental research designs, bias as often motivations were 55

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Table 5.1 Summary of studies exploring underlying motivations for aggression Author/s

Year published

Sample size and nature

Motivations identified

Coid

2002

81 prisoners

Blow to self-esteem Violence only solution Pride in fighting skills Minimal stress tolerance Protest Persistent subversion Intolerance of rules Subdue a rival Homicidal urges Provocation

Olson & Lloyd

2005

25 intimate partners

Restoration of face, Threat removal Self-defense Communication style Family learned pattern Rule violation Gain attention/compliance Personality factors Pain of unresolved issues Control Promote comfort/security Alcohol/drug use state

Graham et al.

2013

1,507 non-clinical adults

Compliance and grievance Social identity concerns Excitement

Urheim et al.

2014

28 clinical inpatients

Irritability Instrumental Defense

Source: Ohlsson (2016)

inferred by researchers from behaviours rather than elicited by self-report, and that the aggression motivation was not the primary focus of some studies.

Aggression motivation, inhibition and reasoned action Prior to describing the Applied Integrated Model of Aggression Motivation (AIM-AM), it is perhaps important to briefly consider theories of human motivation and decision-making more generally. As these theories form the basis upon which this literature is applied to aggression by the AIM-AM. An understanding of this is also helpful to further understand why consideration of motivation in aggression is important. In the motivation literature, two overarching metaphors resulted in alternative types of theories and the subsequent growth in the study of human motivations (Weiner, 1994). Cartesian dualism (Descartes [1596–1650], as cited in Weiner, 1994) described the coexistence of the mind and body. This resulted in considerations of humans as godlike, and their motivations an outcome of logic, knowledge and rational choice. The second, machine metaphor considers human 56

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motivation to be automatic and driven by unconscious forces or habit. Motivation theories have accepted and incorporated these principal metaphors to varying degrees (Weiner, 1994). For instance, psychoanalytic, ethological, socio-biological, drive and Gestalt theories of motivation were guided by the machine comparison. Expectancy-value theories are associated with the godlike metaphor. It is beyond the scope of this chapter to review all theories of human motivation. The core focus of this chapter concerns the AIM-AM and how concepts such as predisposing developmental factors, socio-cognitive processes and affective states are integrated and linked to aggression motivation. This has parallels to expectancy-value theories of behavioural motivation that are primarily discussed. Expectancy-value theories, such as that of Julian Rotter (1954), contend that our actions in any given context are motivated by the perceived likelihood of achieving a desired outcome, the subjective value of this for the individual, any associative costs, and the influence of prior outcomes through reinforcement. Rotter (1954) argued: [T]he potential occurrence of a behaviour that leads to the satisfaction of some need is a function of the expectancies that these behaviours will lead to these reinforcements and the strength or value of these reinforcements. p.110 Rotter’s seminal theory of motivation (1954) noted four key notions including: behavioural potential, expectancy, reinforcement and the psychological situation. Behaviour is therefore determined by our knowledge and selection of the best course of action (Rotter, Chance & Phares, 1972). Expectancy is determined by individuals’ past history and outcomes from comparable situations (Rotter, 1954). It is this expectancy that results in motivating the individual towards a desired action (Rotter, Chance & Phares, 1972; Weiner, 1994). In any discussion of motivation, rational choice and aggression, it is worth considering the Theory of Coercive Action (Tedeschi & Felson, 1994). Aggression, referred to as coercive actions by the authors, is considered to result from a decision process made by the perpetrator to achieve relevant social goals. They define coercive actions as any act undertaken with intent to harm another person and to gain their compliance (Felson & Tedeschi, 1994). This social interactionist perspective argues that aggression always serves a purpose. That is, even reactive, expressive or emotionally driven aggression has an instrumental goal, such as the release of emotional arousal or the satisfaction of having a grievance recognised (Eisner, 2009). Felson and Tedeschi’s (1994) preference of the term coercive action rather than aggression centred on their desire to bridge voids and segregation of knowledge and understanding across disciplines. According to this theory there are three types of coercive actions: threats, punishments and bodily force. These are not to be confused with the three main goals of coercive actions (i.e. to gain compliance, to restore justice and to assert or defend identities), which will be described shortly. Threats were dichotomised into contingent and non-contingent and could be subtle or explicit. They defined punishment as an action performed with intent to harm another. This is consistent with the working definition of aggression discussed in the preceding section of this chapter. Bodily force encompassed the use of physical contact to compel or constrain others’ behaviours. Three major social goals were differentiated as the motivational underpinnings of coercive action. They include: controlling others, restoring justice for perceived wrongs, and asserting or protecting social/self-identity. The decision to aggress is mediated by the expectancy that the goal will be reached, the value of the respective goal and the estimated costs of the behaviour. Thus, rational decision-making is clearly a fundamental principle of the theory of coercive action 57

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(Tedeschi & Felson, 1994). Graham et al. (2013) argue that this theoretical framework provides the most useful taxonomy for understanding aggression motivation in naturally occurring settings. However, very limited systematic research has focused on testing the validity of these motivations for aggression (Graham et al., 2013).

Principles and theoretical basis of the AIM-AM The AIM-AM was developed from three research studies with adult males in the UK (Ohlsson & Ireland, 2011; Ohlsson, 2016). Prior to a detailed discussion of this new model, a summary of the research studies that assisted its formulation is briefly recapitulated.

Study 1: Aggression motivation and emotion (Ohlsson & Ireland, 2011) Two hundred and six adult males participated in this study, which aimed to explore the components of aggression motivation, and their relationship with anger and social desirability. Four self-report questionnaires were utilised towards this aim. Following exploratory factor analysis aggression motivations were separated into four factors (positive outcomes, pleasure, protection, and social recognition and emotional management), as opposed to two (reactive and proactive) or three factors (reactive, proactive and mixed), which is an important finding. Exploratory factor analysis is a statistical method for exploring the structure of data by explaining the relationships between variables, and it summarises large collections of data into smaller related factors. The notion that any distinction based on only two elements (such as reactive vs. proactive with their focus on the presence or absence of emotion, and actions occurring as a result of blocked or intended goals), was found to be too narrow to account for the complexity of human aggression motivation. These results suggested that a more comprehensive framework is required for understanding aggression motivation, and one that moves towards consideration accepting aggression as dynamic and the outcome of multiple underlying motives and causal factors. This study was also one of the first to examine directly the role of emotion, such as anger, specifically with motivation rather than simply with forms of aggression (see Roberton et al., 2012). Anger was demonstrated by this study to be linked to all aggressive motivations. The traditional view that emotion is only associated with certain motivations, such as reactive (Raine et al., 2006), was unsupported. This brought into question the validity of the reactive versus proactive distinction as applied to aggression motivation. This has implications for both researchers and practitioners whose adoption of this distinction for empirical study or clinical decision-making may consequently be flawed. This finding also emphasised that emotion has a prominent and central role in aggression motivation, and is most likely to be a contributory factor along with cognition, given they (cognition and emotion) are both inextricably linked in the literature (Huesmann, 1998; Omadahl, 2014; Schacter & Singer, 1962). In contrast, social desirability was found to be associated with only the positive outcomes and social recognition and emotional management aggression motivations. This suggested that participants were less likely to respond in a socially desirable manner when their recent acts of aggression were motivated by pleasure, whereas aggression used in the pursuit of positive outcomes and social recognition and emotional management resulted more readily in socially desirable behaviour. This finding was consistent with the assertions of the Applied Model of Information Processing (AMIP: Ireland & Murray, 2005), which argued that compared with other socio-cognitive information processing models (i.e. Crick & Dodge, 1994), aggression can serve an adaptive function in certain contexts and conditions, such as in the presence of threats, provocation and 58

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conflict. It is also argued that certain settings provide frequent triggers and reinforcement to aggressive or non-aggressive actions.

Study 2: Aggression motivation, developmental factors and cognition (Ohlsson, 2016) This study continued with the exploration of aggressive motivations, and examined how these related to individuals’ cognitions and developmental experiences. To examine this, 233 adult males completed three previously published and two newly developed self-report measures. Some measures were developed specifically for this research due to its novel focus and the consequent lack of suitable and validated equivalents. In terms of methodology, consideration of participants’ developmental experiences was also retrospective, which could be a limitation, but reliability coefficients for each measure were excellent. There were several important findings from this research. First, a four-factor model of aggression motivation, based on those identified in Study 1 (as described above), was not supported by confirmatory factor analysis. Confirmatory factor analysis is a statistical technique used to verify the structure of a set of variables, in this case aggression, by testing different hypotheses that differing relationships exist. Therefore, a further exploratory factor analysis was undertaken that supported a three-factor structure that concerned motivations related to pleasure and emotional management, protection, and positive social outcomes. This finding added to the expanding evidence that a dichotomous distinction for aggression motivation (i.e. reactive vs. proactive) was not satisfactory. Protection and positive outcomes were themes repeated between Studies 1 and 2; however, a component structure for aggression motivation remained unclear. Second, it was found that aggressors could not be distinguished in terms of their negative developmental experiences. This was contrary to core assumptions made by existing pathway models for aggression, namely the Sequential (Vitaro & Bredgen, 2005) and Parallel Models (Dodge, 1991). Briefly, the parallel model contends that proactive and reactive aggressions originate from different backgrounds and develop independently from one another. Specifically, that reactive aggression arises in response to punitive and harsh parenting, and proactive aggression as a consequence of more permissive parenting approaches that foster the use of such aggression. The sequential model focuses on the role of temperament or neurophysiological factors that predispose early displays of reactive aggression. If reinforced, learning takes place that results in later proactive forms of aggression. Existing developmental models experienced difficulty in accounting for the findings from Study 2, and therefore the need for an alternative developmental perspective was apparent. The idea of a simultaneous development pathway model for aggression is proposed. This simultaneous model draws upon the principles of previous models, such as the notion that one form of aggression can become habitual and develop independently of the other (as described by the parallel model; Dodge, 1991), but also incorporates the principles of individual and environmental reinforcement of aggression (as indicated by the sequential model; Vitaro & Bredgen, 2005). A key difference would be that action reinforcement for motivations occurs simultaneously, and thus strengthens aggressive response tendencies and decisions towards the individual’s capacity to act. Speculatively, this model could explain the resulting development of mixed motive aggression over time through the reinforcement of mixed motives and indeed the presence of multiple motives within the same incident. The new simultaneous pathway proposed by this research has potential to address the limitations of its predecessors, which includes their overfocus on the reactive vs. proactive distinction, difficulties in accounting for multiple motivations, and research findings that the development of aggression do not always adhere to the sequential 59

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or parallel formats (Ireland, 2009). There is need for further validation and testing of this notion and theoretical developmental model, which is discussed in the concluding comments of this chapter. Third, this study found that the core developmental factors related to pleasure-motivated aggressors were problematic childhood behaviours, parenting styles that included elements such as praise and a preoccupied adult attachment. Problematic childhood behaviour was the most influential factor in this motivation. This finding is consistent with literature that indicated poor or misguided parenting is linked to a variety of internalised and externalised difficulties, including aggression (Gershoff, 2008; Stormshak et al., 2000). Yet, the finding that these three factors together reflected a developmental profile representative of pleasure-motivated aggression is novel. Therefore, the mechanisms and processes through which they culminate in this motivation for aggression remain unclear. As advocated by many existing integrated theories of aggression, developmental factors alone are not solely responsible for aggression, with factors in other domains such as cognition, affect and personality being of importance (Ferguson et al., 2008; Huesmann & Taylor, 2006). Only negative childhood experiences characterised by maltreatment featured in the developmental profile for protection-motivated aggressors. This suggested that the developmental factors underlying this motivation are quite distinct, a finding consistent with previous research that suggested negative childhood experiences and early maladjustment have long-lasting psychological and behavioural impacts throughout life (Finkelhor et al., 2011). Such experiences were seen to have a contagion effect influencing individuals’ cognitions, social informationprocessing that favoured hostile attributions and responses, and emotional functioning (MurrayClose et al., 2009). Whilst other studies have linked negative childhood experiences to general aggression (i.e. Sarchiapone et al., 2009; Kolla et al., 2013), this study was the first to examine their influence on underlying aggression motivation. Therefore, the finding of a single predictive characteristic should not be viewed as a limitation, especially given the wider domains potentially influenced by developmental factors, such as cognition, personality and emotion regulation. Problematic childhood behaviours, negative childhood experiences and dismissive avoidant adult attachments featured as developmental factors most relevant to the positive social outcomes aggression motivation. This developmental profile is interesting given that it shares factors (i.e. negative childhood experiences and problematic behaviours) with other motives (i.e. pleasure and protection). Previous research has identified links between these factors individually and general aggression (Corvo, 2006). The most prominent factor in this profile is the adult dismissiveavoidant attachment style, given that it was not indicated in any other profiles. Insecure adult attachments are formed in childhood, as negative experiences influence internal working models and cognitive behavioural systems throughout life (Bowlby, 1988). The finding that no attachment styles were sole factors in a developmental profile of aggression motivation is consistent with arguments in the literature that the relationship between attachment and aggression could never be causal (Calkins & Leerkes, 2011). This study, therefore, added to the limited knowledge of the role of attachment in aggression motivation (Savage, 2014). It also indicated how single and multiple item developmental profiles exist for each aggression motivation. Cognition was examined in Study 2, as it has long been indicated that aggression originates from biased cognitions and deficiencies in social information processing (Anderson & Bushman, 2002; Crick & Dodge, 1994). Emotional arousal increases any misinterpretation with cognition and emotion both linked to aggression (Huesmann, 1998). Study 2 addressed gaps left by previous research through examining the specific associations between cognition (i.e. beliefs and schemata) and aggression motivations. 60

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Study 2 examined whether normative beliefs were important in the new aggression motivations identified (i.e. pleasure and emotional management, protection and positive social outcomes). It was found that only participants motivated to aggress by positive social outcomes had elevated numbers of normative aggression beliefs. Essentially this evidence indicated that certain normative beliefs could be more important in some aggression motivations than others. This was further supported by findings that two particular beliefs (i.e. ‘if someone is aggressive towards you it’s okay to be aggressive back’ and ‘aggression is needed to stop others walking over you’) were predictors of aggression motivated by protection. This evidence indicated that the underlying beliefs influencing aggression motivations, such as positive social outcomes and protection, are distinct. It also suggested that normative beliefs may not be important in other motivations, such as pleasure, which could be underpinned by other factor/s such as personality and/or affect. This is consistent with views that the influence of social-cognition in all forms of aggression is overstated (Ferguson et al., 2008). The importance of cognitive schemata in aggression was also highlighted in this study. Young et al. (2003) described an evolutionary basis for schemata with further life-course events reinforcing maladaptive and adaptive cognitions. Few prior studies had explored the influence of schemata on aggression, and none had examined adaptive and maladaptive schemata and their association with aggression motivation. This study was novel as it examined cognition and aggression motivation, and therefore is highly relevant to our understanding of the underlying cognitive characteristics of aggression. Young et al. (2003) stated that negative influences from others and/or trauma have a role in the development of maladaptive schemata. In relation to schemata intolerant of others, for example, this would suggest there has been developmental learning that others are irritating, uncaring and interpersonal relationships not worthy of attention. This is relevant to the finding that some cognitive schemata were predictors of certain aggression motivations (such as protection) and highlights the potential aetiological and cognitive factors important in the formation of this aggression motivation. The view, however, that aggression is solely underpinned by maladaptive schema was challenged by the results of this study. Elevated rates of the positive schemata in general and individual schemata (i.e. calm and controlled), were associated with participants’ aggression motivated by positive social outcomes. The mere presence of positive schemata may be insufficient to thwart aggression as some had previously considered (Milner & Webster, 2005). This study indicated that even positive schemata, such as being hardworking or easy going, could associate with aggression in certain circumstances (Ireland & Murray, 2005). The need for a broader and multifaceted approach to treatment and research considering cognitive schemata and aggression is, therefore, illustrated.

Study 3: Aggression motivation and inhibition, personality and regulation (Ohlsson, 2016) Building on the previous two studies, this research further examined the components of aggression motivation and inhibition, and their association with interfering personality disorder traits and emotion regulation strategies. Two hundred and thirty-four adult males participated in this study. Each completed three published self-report measures (exploring aggression motivation, personality and emotion regulation) and one measure (Aggression Inhibition Questionnaire) that was created specifically for this study as one was not available in the literature. Two of the most prominent emotion regulation strategies, cognitive reappraisal and expressive suppression (Gross, 2014) were considered. Traits of the ten recognised personality disorder traits by current classification systems were considered. 61

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The most important findings from this study were as follows. First, the three-factor solution for aggression motivation identified in Study 2 was supported as a good fit with these data by confirmatory factor analysis. This model essentially consisted of positive social outcomes, pleasure and emotional management and protection motivations. This indicated that the existing specified distinction for aggression motivation, as either reactive or proactive (Raine et al., 2006), was not supported, confirming concerns in the literature relating to the oversimplified and generalised use of this distinction (Bushman & Anderson, 2001; Ireland, 2011). The finding that some motivations, such as protection and pleasure, demonstrated stability between studies supported contentions described by motivational theorists, that even diverse behaviours could be driven by few underlying motives (Reiss, 2004). These motivational components were also found in other studies (i.e. Urheim et al., 2014) adding to their validity and importance in conceptualising aggression motivation. Second, somewhat consistent with previous research (Finkel, 2007), a four-factor model of aggression inhibition was found using exploratory factor analysis. This included the components; empathy and consequence evaluation, lack of success and need to protect self, traits and beliefs unsupportive of aggression and emotional control. However, not all these components were entirely aligned with existing frameworks. For instance, some parallels may be drawn between Finkel’s (2007) personal and situational inhibitors and this study’s components of traits and beliefs unsupportive of aggression and lack of success and need to protect inhibitors, respectively. Yet clear differences emerge with regard to the empathy and consequence evaluation and emotional control inhibitors, which also cannot be easily accounted for by other frameworks. It is unclear whether these differences emanate from sample variations, or differences in terms of the nature of the frameworks themselves (i.e. theoretical versus applied). For instance, it would be challenging to assess comprehensively the influence of evolutionary inhibitors practically, whilst it would not be possible to refute the evolutionary basis of aggression theoretically (Tremblay, Hartup & Archer, 2005). Third, certain maladaptive personality traits were found to be predictors of individual aggression motivations. In particular, the personality characteristics of antisocial, narcissistic or schizoid traits predicted aggression motivated by positive social outcomes. A profile inclusive of antisocial and dependent traits was related to aggression motivated by protection. Borderline and antisocial traits were further predictors of the pleasure aggression motivation. These findings are important given that only one personality trait predicted more than one aggression motivation. Antisocial personality traits were ubiquitous to all aggression motivations, suggesting they could reflect a more generic personality marker for aggression. Its core traits, including disregard for rules and willingness to violate the rights of others toward one’s personal interests, could explain its broader association to these varying aggression motivations. The fact that the majority of maladaptive personality traits were more specific in terms of their association to each motivation is important. It indicates the possibility that personality profiles for each motivational distinction can be identified, which contrasts with the view that all traits are relevant to all forms of aggression. It is not being suggested here that each individual has only one distinct personality-to-aggression motivation profile. It is perhaps likely that the same individual could have different profiles at different times and these contribute to their habitual use of aggression. Identification of distinct personality profiles for each aggression motivation could have wide-ranging implications, particularly if considered in terms of their core characteristics, and how these combine and interact with other factors (such as cognition and/ or affect) to influence decision-making to engage in aggression is important. Furthermore, this study identified that certain personality traits inhibited aggression. Obsessive–compulsive personality traits, for example, predicted the lack of success and need to protect self inhibitor. In contrast, avoidant and schizoid traits predicted the inhibitor traits and beliefs 62

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unsupportive of aggression. It could be that underlying characteristic features of these traits (i.e. sensitivity to negative evaluation and avoidance of social situations and interactions as found with maladaptive avoidant personality) function to promote non-aggression in certain circumstances. For example, avoidant individuals may relinquish their position in a conflict situation with another and not engage in aggression due to concerns over being evaluated negatively by others. The mechanisms and processes underlying the relationship between personality and nonaggression, however, remain unclear and could not be ascertained from this research due to its exploratory nature and relatively narrow consideration of aggression inhibition. The fact that some aggression inhibitors were found to be unrelated to personality is important and suggestive of the involvement of other factors. This would fit with the view of other researchers (i.e. Nestor, 2014) that in combination with other factors, personality can influence the magnitude and direction of behavioural actions. It is conceivable that these underlying factors could include a variation of the emotional, cognitive and developmental factors that influence aggression motivation. Further research would be needed to prove or disprove this premise. Nonetheless, there is a need for integrated models of aggression to recognise the more specific role of personality in aggression motivation and inhibition, as this appears inadequately considered and addressed in existing integrated theories (Ferguson et al., 2008). Study 1 found emotion, notably anger, was related to all aggression motivations. Therefore, emotion regulation was an important avenue of investigation, and its significance with regards to aggression and non-aggression was demonstrated. Expressive suppression, for instance, predicted use of the protection aggressive motive and the lack of success and need to protect the self inhibitor. The finding that emotional suppression was linked with aggression is consistent with the literature (Roberton et al., 2012). Cognitive reappraisal and expressive suppression were, however, not related to all aggression motivations and inhibitors. No significant associations were found with pleasure or positive social outcomes motivations, or with the empathy and consequence evaluation inhibitor. This could be due to the fact that only two regulatory strategies were studied from a number of other possibilities (Gross & Thompson, 2007). It could also be that emotion regulation does not have a salient underlying role in the culmination of these motivations or inhibitors. This is plausible given that evidence from the current and previous studies implicated developmental, personality and cognitive factors as being more influential to these motivations and inhibitors. The literature indicates that cognition and emotion are related concepts. This was further evident when the emotion regulation data were examined, as the regulation strategy of expressive suppression predicted the inhibitory component traits and beliefs unsupportive of aggression. Cognitive re-appraisal was also the strongest predictor of the emotional control inhibitor. In the aggression literature, cognition and emotion are considered united in their creation of an internal state that induces aggression (Anderson & Bushman, 2002). The current research indicated cognition and emotion could equally induce an internal state that inhibits as well as motivates aggression. This adds further weight of evidence to the contention of this research and current chapter that similar underlying factors (i.e. cognition, affect, developmental and personality) could underlie aggression and non-aggression, with differences in their content and characteristics resulting in alternative outcomes. How these factors relate and manifest in these outcomes is formulated by the AIM-AM, which is considered next.

Applied Integrated Model of Aggression Motivation (AIM-AM) The Applied Integrated Model of Aggression Motivation (AIM-AM) is presented diagrammatically in Figure 5.1. It is represented as a Knowledge Integration Map (KIM) of insight gained into 63

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