The Attraction of Religion: A New Evolutionary Psychology of Religion 9781472534620, 9781472594617, 9781472531728

Religion is an evolutionary puzzle. It involves beliefs in counterfactual worlds and engagement in costly rituals. Yet r

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Table of contents :
Cover
Half-title
Title
Copyright
Dedication
Contents
List of Contributors
List of Figures
Introduction: Connecting Religion, Sex, and Evolution
1. Why Don’t Abstinence Education Programs Work? (And Other Puzzles): Exploring Causal Variables in Sexual Selectionist Theories of Religion
CSR and the Swiss army knife mind
Religion as a variable
Mating strategies
Religion and mating behavior
Religiosity and group-level effects
Conclusion
2. Religion and Parental Cooperation: An Empirical Test of Slone’s Sexual Signaling Model
Fidelity and social reputation
Theoretical predictions
Results
Prayer and fertility
Discussion
Methodological contribution
Theoretical contribution
Limitations and future research
Appendix
3. How Is’t With Thy Religion, Pray? Selection of Religiosity Among Individuals and Groups
Cooperative breeding in human evolution
Successful religious communities are strongly supported by women
Social cognitions and signals
Were early religious networks founded by women?
Conclusion
4. Losing My Religion: An Analysis of the Decline in Religious Attendance from Childhood to Adulthood
Reproductive religiosity
Expanding the model
The NLSY97 sample and variables
The lifestyle context of young-adult religious transitions
Conclusion
5. Costly Signaling Theory, Sexual Selection, and the Influence of Ancestors on Religious Behavior
Costly religious behaviors that never pay off during the lifetime of the altruist
The influence of ancestors and a solution to the puzzle of the Golden Rule
Conclusion
6. When Religion Makes It Worse: Religiously Motivated Violence as a Sexual Selection Weapon
Evolutionary psychological perspectives on violence
Sexual selection, parental investment, and religiously motivated violence
Future directions
Conclusion
7. The Dividends of Discounting Pain: Self-Inflicted Pain as a Reputational Commodity
The conundrum of extensive cooperation
Costly signals
Methods
Findings
Specific findings and exemplary study cases
Discussion
Conclusion
8. False Advertising: The Attractiveness of Religion as a Moral Brand
9. Fathering, Rituals, and Mating: Exploring Paternal Stability and Sexual Strategies in Early Religious Practices
Paternal care
Evolution and fathering
Religion, rituals, and evolution
Incentivizing behaviors—ritual as attraction
Conclusion
10. The Evolutionary Psychology of Theology
Theology as the product of evolutionary selection
Adaptationism
Spandrelism
Towards a reconciliation of the adaptationist and spandrelist paradigms
Conclusion
Notes
Bibliography
Index
Recommend Papers

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The Attraction of Religion

Scientific Studies of Religion: Inquiry and Explanation Series editors: Luther H. Martin, William W. McCorkle, and Donald Wiebe Scientific Studies of Religion: Inquiry and Explanation publishes cuttingedge research in the new and growing field of scientific studies in religion. Its aim is to publish empirical, experimental, historical, and ethnographic research on religious thought, behavior, and institutional structures. The series works with a broad notion of “scientific” that will include innovative work on understanding religion(s), both past and present. With an emphasis on the cognitive science of religion, the series includes complementary approaches to the study of religion, such as psychology and computer modeling of religious data. Titles seek to provide explanatory accounts for the religious behaviors under review, both past and present. Religion in Science Fiction, Steven Hrotic The Mind of Mithraists, Luther H. Martin

The Attraction of Religion A New Evolutionary Psychology of Religion D. Jason Slone and James A. Van Slyke

Bloomsbury Academic An imprint of Bloomsbury Publishing Plc

Bloomsbury Academic An imprint of Bloomsbury Publishing Plc 50 Bedford Square London WC1B 3DP UK

1385 Broadway New York NY 10018 USA

www.bloomsbury.com BLOOMSBURY and the Diana logo are trademarks of Bloomsbury Publishing Plc First published 2015 Paperback edition first published 2016 © Jason Slone, James Van Slyke, and Contributors, 2015 Jason Slone and James Van Slyke have asserted their rights under the Copyright, Designs and Patents Act, 1988, to be identified as Editors of this work. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage or retrieval system, without prior permission in writing from the publishers. No responsibility for loss caused to any individual or organization acting on or refraining from action as a result of the material in this publication can be accepted by Bloomsbury or the author. British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ISBN: HB: 978-1-472-53462-0 PB: 978-1-350-00528-0 ePDF: 978-1-472-53172-8 ePUb: 978-1-472-52968-8 Library of Congress Cataloging-in-Publication Data The attraction of religion : a new evolutionary psychology of religion / edited by D. Jason Slone & James A. Van Slyke. pages cm. -- (Scientific studies of religion: inquiry and explanation) Includes bibliographical references and index. ISBN 978-1-4725-3462-0 (hardback : alk. paper) 1. Psychology, Religious. 2. Evolutionary psychology. I. Slone, D. Jason, editor. BL53.A89 2015 200.1'9--dc23 2014044604 Series: Scientific Studies of Religion: Inquiry and Explanation Typeset by Fakenham Prepress Solutions, Fakenham, Norfolk NR21 8NN Printed and bound in Great Britain

To Andrew and Nicholas Jason Slone To Abby and Kail James Van Slyke

Contents List of Contributors List of Figures

ix xv

Introduction: Connecting Religion, Sex, and Evolution  Jason Slone and James A. Van Slyke 1 1 Why Don’t Abstinence Education Programs Work? (And Other Puzzles): Exploring Causal Variables in Sexual Selectionist Theories of Religion  James A. Van Slyke 2 Religion and Parental Cooperation: An Empirical Test of Slone’s Sexual Signaling Model  Joseph Bulbulia, John Shaver, Lara Greaves, Richard Sosis and Chris G. Sibley 3 How Is’t With Thy Religion, Pray? Selection of Religiosity Among Individuals and Groups  Michael Blume 4 Losing My Religion: An Analysis of the Decline in Religious Attendance from Childhood to Adulthood  Jason Weeden 5 Costly Signaling Theory, Sexual Selection, and the Influence of Ancestors on Religious Behavior  Craig T. Palmer and Ryan O. Begley 6 When Religion Makes It Worse: Religiously Motivated Violence as a Sexual Selection Weapon  Yael Sela, Todd K. Shackelford, and James R. Liddle 7 The Dividends of Discounting Pain: Self-Inflicted Pain as a Reputational Commodity  Matthew Martinez and Pierre Lienard 8 False Advertising: The Attractiveness of Religion as a Moral Brand  Panagiotis Mitkidis and Gabriel Levy 9 Fathering, Rituals, and Mating: Exploring Paternal Stability and Sexual Strategies in Early Religious Practices  David Bell

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29 63 73

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111 133 159 169

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10 The Evolutionary Psychology of Theology  Andrew Mahoney

189

Notes Bibliography Index

211 215 247

List of Contributors Ryan O. Begley is a doctoral candidate at the University of Missouri, USA, where he studies human sociocultural behavior from an evolutionary perspective. Primarily ethnological, his research includes generating and testing Darwinian explanations of human communication (as influence), with an emphasis on the long-term effects of traditional stories/storytelling. David Bell is the Senior Lecturer in Religion and Science at Georgia State University, USA. He studied with James Loder (Princeton) and John Snarey (Emory) in developmental psychology and religion. His doctoral dissertation (PhD, 2009, Emory) focuses on religious identity, both in its cognitive foundations and in the development of a psychometric tool for research. He regularly teaches interdisciplinary courses using both anthropological and psychological approaches to religious phenomena. Michael Blume was born in 1976 in Filderstadt, Germany. He currently teaches Religionswissenschaft (Scientific Study of Religion) at the Universities of Jena and Cologne, Germany. His promotional thesis focused on theories of religion in the brain sciences (the so-called “neurotheologies”). He then specialized in the reproductive potentials of religiosity—the complex workings of religious communities augmenting cooperation, birth, and survival rates (and thus evolutionary fitness). He has published a range of German science books, is part of a Christian-Muslim family and a father of three. Joseph Bulbulia is a Reader in Religious Studies at Victoria University, New Zealand, where he has taught since 2000. He is a core member of the New Zealand Attitudes and Values Study (NZAVS), a 20-year longitudinal study of attitudes, values, and faith in a large and diverse sample of New Zealanders. He has published in the areas of signaling theory, cultural evolution, charity, ecology, and well-being. He is currently President of the International Association for the Cognitive Science of Religion.

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List of Contributors

Lara Greaves (Ngāti Kurī, Te Āti Awa, Ngāpuhi) is a master’s student in the School of Psychology, Victoria University, New Zealand, working with the New Zealand Attitudes and Values Study (NZAVS). She co-authored numerous scientific papers while still an undergraduate student. She is the NZAVS lab manager, and a core member of the management team that runs the NZAVS. Her research focuses on statistically modeling longitudinal change in Maori identity, health, and well-being, and also voting behavior and political attitudes. Gabriel Levy is Associate Professor in the Science of Religion at the Norwegian University of Science and Technology in Trondheim, Norway, where he teaches on method and theory in the scientific study of religion, Middle Eastern religious history with a focus on Judaism, and the relation between religion, science, and technology. His research is devoted to the comparative history of religion, specializing in Jewish studies. His most recent book uses insights from biology and the mind sciences to explore the effects of literacy on religious cognition and the origins of Judaism. He has just begun research for his second book, which will explore the subject of intimacy from a broad historical perspective, but also the ways in which religions, and Judaism in particular, modulate intimacy. James R. Liddle (www.jamesrliddle.com) is a doctoral student in the Evolutionary Psychology PhD program at Florida Atlantic University, USA. He is a member of David F. Bjorklund’s evolutionary developmental psychology lab and is coadvised by Todd K. Shackelford at Oakland University. His research interests focus primarily on the origin and development of religious beliefs and behaviors. He is currently investigating the societal factors that influence religiosity. He also serves as the production manager for the online journal Evolutionary Psychology (www.epjournal.net). Pierre Lienard is Associate Professor in the Department of Anthropology at the University of Nevada, USA. He has conducted in-depth ethnographic research among pastoralists of East Africa, on their collective rituals, political systems, and institutions. He has focused part of his research agenda on the study of individual and collective ritualized behavior, and the latter’s role



List of Contributors

xi

in the process of symbolic evocation and the establishment of leadership and authority. He is also investigating precaution psychology, cooperation, coalitional dynamics, and coordination, and trust and exchange in conditions of environmental and political uncertainty in decentralized or weakly centralized systems. He has been published in high-profile publications and first-tier journals (Behavioral and Brain Sciences, American Anthropologist, Neuroscience and Biobehavioral Review, Oxford University Press, PLOS ONE). Andrew Mahoney graduated from Victoria University, New Zealand in 2011 with a PhD in the evolutionary psychology of religion. His dissertation examined the social and biological bases for the human tendency to acquire complex supernatural knowledge. He currently works as a Social Science Advisor for the New Zealand Government’s Department of Conservation and he delivers occasional guest lectures on the psychology of religion at Victoria University. Matthew Martinez is a doctoral student in the Department of Anthropology at the University of Nevada, USA. He works with Pierre Lienard as a member of the Society, Evolution, and Culture Lab research team. His research interests include cooperation, coordination, and signaling; cultural evolution; and evolutionary psychology. Currently, he is studying the phenomenon of voluntary and painful religious practices in cross-cultural contexts. Panos (Panagiotis) Mitkidis is Assistant Professor of Behavioural Economics and Experimental Anthropology at Aarhus University, Denmark, and visiting Assistant Professor at Duke University, USA. He is aligned with three research centres, the Center for Advanced Hindsight (CAH) at Duke University, the Interacting Minds Centre (IMC), and the Interdisciplinary Centre for Organisational Architecture (ICOA) at Aarhus University. His research interests span a wide range of behaviors but his main focus is on the brighter and darker sides of cooperation and how we can promote its positive aspects. In doing so, he combines empirical observations generated from both laboratory- and field-settings behavioral experiments. His work has been featured in leading scholarly journals and a variety of popular media outlets,

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List of Contributors

including PloS One, Psychological Science, Microsoft, Medical News Today, and TEDx. Craig T. Palmer is an Associate Professor of Anthropology at the University of Missouri, USA. His research focuses on incorporating cultural traditions into evolutionary explanations of human behavior. His publications include co-authored books on religion (The Supernatural and Natural Selection), sexual aggression (The Natural History of Rape), the ecological collapse of the Canadian cod fishery (When the Fish are Gone), and altruism (Kindness, Kinship and Tradition in Newfoundland/Alberta Migration). Yael Sela (www.yael-sela.com) is a doctoral student in the Experimental Psychology PhD program at Oakland University, USA, working in Todd Shackelford’s evolutionary psychology lab. She applies an evolutionary perspective to her two main research interests, which are human sexual psychology in the context of inter-sexual conflict, and the developmental psychology of religiosity. She is currently investigating female sexual psychology within the framework of sperm competition theory, and the developmental outcomes of childhood religious experiences. Todd K. Shackelford received his PhD in evolutionary psychology in 1997 from the University of Texas at Austin, USA. He is Professor and Chair of the Department of Psychology at Oakland University, USA, where he is director of the evolutionary psychology lab (www.ToddKShackelford.com). He has published more than 300 peer-reviewed articles and chapters in edited volumes and has co-edited 13 volumes. Much of his research addresses sexual conflict between men and women, with a special focus on testing hypotheses derived from sperm competition theory. Since 2006, he has served as editor of Evolutionary Psychology (www.epjournal.net). John H. Shaver is a lecturer and postdoctoral research fellow at Victoria University, New Zealand. He is an anthropologist whose work seeks to understand the evolution of human life histories and the dynamics of religious change. To investigate these issues, he has conducted research in the Czech Republic, Fiji, Mauritius, New Zealand, and the United States.



List of Contributors

xiii

Chris Sibley is an Associate Professor in the School of Psychology at the University of Auckland, New Zealand. He teaches in research methods and has published more than 150 peer-reviewed articles and book chapters in areas such as personality, political psychology, and intergroup relations. He is the lead investigator for the New Zealand Attitudes and Values Study (NZAVS), a 20-year longitudinal national probability study of social attitudes, personality, and health outcomes. Jason Slone is Associate Professor of Psychology and Humanities in the School of Arts and Sciences at Tiffin University, Ohio, USA. He is the author of Theological Incorrectness: Why Religious People Believe What They Shouldn’t (Oxford University Press, 2004), editor of Religion and Cognition: A Reader (Routledge Press, 2006), and has published a number of theoretical and empirical articles on the evolutionary psychology of religion. He was the Hardigg Lecturer in the Department of Religion at Dartmouth College, USA in 2006. Richard Sosis is James Barnett Professor of Humanistic Anthropology and Director of the Evolution, Cognition, and Culture Program at the University of Connecticut, USA. His work has focused on the evolution of cooperation and the adaptive significance of religious behavior, with particular interest in the relationship between ritual and intra-group cooperation. To explore these issues, he has conducted fieldwork with remote cooperative fishers in the Federated States of Micronesia and with various communities throughout Israel. He is co-founder and co-editor of the journal Religion, Brain & Behavior, which publishes research on the biological study of religion. James A. Van Slyke is Assistant Professor of Psychology at Fresno Pacific University, USA, and his research focus is in the areas of psychology of religion, moral psychology, and religion and science. His first book was The Cognitive Science of Religion (Ashgate Press, 2011), and he also co-edited a book entitled Theology and the Science of Moral Action: Virtue Ethics, Exemplarity and Cognitive Neuroscience (Routledge Press, 2012). He recently contributed a chapter entitled “Moral psychology, neuroscience, and virtue: From moral judgment to moral character” in the edited collection, Virtues

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List of Contributors

and their Vices (Oxford University Press, 2014). He has also published articles in Zygon and Theology & Science and is a former Tobis Fellow at the UCI Interdisciplinary Center for the Scientific Study of Ethics and Morality. Jason Weeden is a senior researcher with the Pennsylvania Laboratory for Experimental Evolutionary Psychology and a lawyer in Washington, DC, USA. He received his PhD in psychology from the University of Pennsylvania and conducted post-doctoral research in the Evolutionary Social Cognition Lab at Arizona State University. He is the co-author with Robert Kurzban of The Hidden Agenda of the Political Mind (Princeton University Press, 2014).

List of Figures Figure 2.1: Expected fertility effects associated with prayer rate and church attendance.48 Figure 2.2: Histograms showing frequencies of children, prayer, and church attendance for women, men, and the combined sample of religious respondents.54 Figure 3.1: Old Older Amish in the twentieth century Figure 10.1: The doctrinal mode

67 202

Figure 10.2: How the doctrinal mode began; and how the doctrinal mode resolves the need for large scale cooperation 206

List of Tables Table 2.1: Bivariate correlations between all continuous variables that were modeled to test sexual signaling theory predictions. 36 Table 2.2: Regression model predicting belief in God and religious ingroup commitment.37 Table 2.3: Regression model predicting sex differences in average frequency of prayer for those who prayed and probability of not praying at all among the 39 sample of religious respondents. Table 2.4: Regression model predicting sex differences in average frequency of church attendance for those who attended church and probability of not attending church at all among the sample of religious respondents. 41 Table 2.5: Regression model predicting sex differences in the average number of children for those who were parents and probability of not being a parent among the entire sample of religious and nonreligious respondents. 43

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Table 2.6: Regression model predicting the association between rates of prayer and church attendance with the average number of children for those who were parents and probability of not being a parent for religious participants. 45 Table 3.1: Marriage and fertility rates by religious group.

66

Table 3.2: Muslim women should wear headscarves. Poll among German Muslims 2007. 69 Table 4.1: Religious attendance by number of children born and number of children in home. 74 Table 4.2: Correspondence between religious attendance of parents in 1997 (when offspring were teenagers) and offspring at age 26. 75 Table 4.3: Predicting number of times attending religious services per year using categorical lifestyle predictors. 81 Table 4.4: Predicting number of times attending religious services per year using categorical lifestyle predictors. 86 Table 4.5: Summary of Table 4.4 regression results: Per-year attendance estimates for different sample categories. 87 Table 4.6: Relationship among parental religious attendance, lifestyles, and offspring religious attendance. 88 Table 4.7: Average offspring attendance rates, split out by parental attendance and lifestyle profiles. 89 Table 7.1: Combined features: Voluntariness and publicity.

144

Table 7.2: Combined features: Voluntariness and participation.

144

Table 7.3: Combined features: Publicity and participation.

144

Table 7.4: Population breakdown for all practices.

145

Table 7.5: Combined features: Publicity (full access) and voluntariness, breakdown by society types. 145 Table 7.6: Coerced practices, breakdown by society types.

145

Introduction Connecting Religion, Sex, and Evolution Jason Slone and James A. Van Slyke

From an evolutionary perspective religion is a puzzle. It involves cognitive commitments to non-natural and counterfactual concepts and behavioral commitments to costly and seemingly useless rituals. Yet religion appears to be a human universal (Brown, 1991). Why? What could be the evolutionary psychological explanation(s) for this phenomenon? This volume provides evolutionary descriptions for the existence of religion in human cultures using insights and findings from sexual selection theory in evolutionary psychology. Several prominent evolutionary theories of religion emerged in the nineteenth century, during the era when evolutionary theory began to take hold in the scientific community. Though a number of theories were offered to explain religion, the most prominent were those put forth by the anthropologists E. B. Tylor and James Frazer, the psychoanalyst Sigmund Freud, the economist Karl Marx, and the sociologist Emile Durkheim (Pals, 2006). Tylor and Frazer argued that religion was attractive to people because it offered non-/pre-scientific peoples a way to explain the world and its workings (Tylor, 1903). Freud argued that religion is attractive to people because it helps people to cope with existential fears and anxieties such as pain, suffering, and death, and it helps to “civilize” society by encouraging morality via the repression of selfish, antisocial desires (Freud, 1961). Marx argued that religion is attractive to poor people because of its attractive narrative of rewards in the afterlife, and it is attractive to the rich and powerful because it helps to subdue the labor force by instructing them to accept the status quo as part of God’s plan (Marx, 1843/2000). Durkheim argued that religion is useful because it helps to cohere individuals into groups by facilitating a sense of community among otherwise

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unrelated individuals, exploiting what modern evolutionary psychologists might call fictive kin effects (Durkheim, 1995). In addition, over the past few decades a number of evolutionary psychologists and anthropologists have offered new (or revised) evolutionary accounts of religion. Broadly these accounts fall into two camps—the “spandrelists” and the “adaptationists.” The spandrelists have argued that religion is not an evolved trait per se but rather is a memetic artifact that is a human universal because it enjoys cultural transmission advantages due to its fit with cognitive biases that evolved for other purposes (Boyer, 2003; Dennett, 2006; Guthrie, 1993; Lawson & McCauley, 1990; Slone, 2004). In contrast, the adaptationists have argued that religion evolved to serve the purpose of facilitating cooperation among individuals and groups by punishing moral transgressors and free riders, generating a sense of community through collective rituals, and other forms of social cooperation (Bulbulia, 2008; Sosis & Alcorta, 2003; Whitehouse, 2004; Wilson, 2002). This volume adds to the literature by offering an alternative evolutionary approach to explaining religion that draws on sexual selection theory in evolutionary psychology. Sexual selectionist accounts of religion have been offered in theoretical form by Buss (2002) and Slone (2008), and several important papers have been published on the topic in recent years (Kurzban, Dukes, & Weeden, 2010; Li et al., 2010; Weeden et al., 2008). Collectively, these papers laid the foundation for the arguments presented in the chapters of this volume arguing that religion may be widespread because, among other factors, it helps people to solve adaptive problems related to reproduction. Sexual selection theory argues that a number of traits and behaviors we see in sexually reproducing species evolved because they help to facilitate not survival per se but rather reproductive success by either making the individual attractive to the opposite sex or by deterring same-sex rivals (Andersson, 1994; Darwin, 1871; Ridley, 1993). Central to sexual selection theory is the hypothesis that many traits and behaviors that facilitate reproductive success are signals of strategic information designed to attract, acquire, and retain mates among the most effective signals are those which are costly and useless because, by being hard to fake, they are reliable indicators of an individual’s fitness. The classic example of such a costly signal is the peacock’s tail.

Introduction

3

Similarly, evolutionary psychologists have argued that a number of human cultural behaviors—such as fashion, art, music, cosmetics, the conspicuous consumption of useless goods like jewelry and large houses, etc.—function as costly signals designed to attract and acquire mates and out-compete rivals (Miller, 2001; Ridley, 1993). In this vein, the central hypothesis explored in this volume is that religion is widespread because it is attractive to people, and it is attractive to people because it helps to manage the suite of adaptive problems related to reproduction via the costly signaling of strategic information useful for attracting, acquiring, and retaining mates, ensuring paternity certainty, preventing mate defection and infidelity, encouraging parental investment, and more. Collectively, the chapters in this volume explore this hypothesis from a variety of angles. In Chapter 1, James Van Slyke explores the philosophical question of whether religion is a causal factor in human behavior by looking at specific cases in which religious communities attempt to manage behavior, such as abstinence education programs. Religion presents unique challenges as a causal variable for a variety of different forms of social behavior, especially as studied in the psychology and sociology of religion. One of the primary challenges is philosophical. What is the direction of causality? Is religiosity an evolved trait that influences and constrains social behavior or is religious behavior a by-product of other evolutionary adaptations? A second, empirical question is how does religion influence behavior? That is, what mechanism in religion causes changes in behaviors and thoughts in the minds of religious people—including sexual behavior? Historically, many religions contain different laws and norms that purportedly influence sexual choices and relationships. Yet, the empirical data leave many questions unanswered. Do faith-based abstinence programs change adolescent behaviors regarding sexual activity? Do persons make decisions regarding sexual choice and preference based on the influence of a particular religion? How could such influences be measured? Sexual selection theory and related hypotheses from evolutionary psychology may offer new explanations for the relationship—perhaps causal—between religion and sexuality. Furthermore, the cognitive science of religion, a sub-field of the evolutionary psychology of religion, explores the relationship between different features of human cognition and the formation and function of religion. Much of this

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research has centered on the cognitive content of religious beliefs such as supernatural agents or the different cognitive mechanisms involved in ritual participation. Van Slyke argues that sexual selection theory offers the cognitive science of religion a new avenue to explore evolved cognitive tendencies involving mating preferences and strategies and their relationship to religious cognition. Religion enhances particular functions of mating cognition, in that certain features of religion overlap with different functional aspects or goals that support and facilitate long-term mating strategies. In Chapter 2, Joseph Bulbulia, John Shaver, Lara Greaves, Richard Sosis, and Chris Sibley explore data that suggests that commitment to religiosity is a way to strategically signal commitment to the “family” values of long-term pair-bonding and fertility. Sex is a cooperation dilemma. Successful reproduction requires accurately assessing the qualities of potential mates. Sexual signaling theory predicts that religion evolved, at least in part, to enable mate discrimination (Slone, 2008). Bulbulia et al. test these hypotheses by assessing whether religious signaling is associated with religious commitment and fertility. Their data come from a large and diverse sample of the people of New Zealand as a part of the NZAVS (New Zealand Attitudes and Values Study; n = 4,377 total; n = 1,647 religious-identified). Results indicated that women were more likely than men to express religion through behaviors associated with fidelity (prayer). Men were more likely than women to express religion through behaviors associated with social prestige (church-attendance). These religious behaviors were associated with greater fertility. Results held when adjusting for key demographic variables, denominational clustering, and zero-inflated response data. Their findings provide preliminary evidence in support of Slone’s theory that religious signals facilitate successful mate selection, and in this way, contribute to the cooperation of parents. In Chapter 3, Michael Blume explores demographic data on reproduction rates among various religious and non-religious groups as a means of evaluating the claim that religion facilitates reproductive success and, by extension, wrestles with the philosophical problem of whether religion is selected for at the level of the individual or group. Being members of our contemporary scientific culture, we easily tend to perceive mate selection as a purely individualistic endeavor taking place among isolated rationalist agents in a

Introduction

5

kind of free market of marriage. But these assumptions are not able to explain the available findings concerning religion and sexual selection, nor are they conveying a realistic picture of human evolutionary and religious history. Being cooperative breeders, human survival and reproduction depended not only on individual contributions, but also on the quality of social environments, including religious networks and (later) groups. Blume argues that sexual selection of religious traits may be better understood as a pragmatic evaluation of individual loyalty and social capital than as a purely individualistic atomistic quality. In Chapter 4, Jason Weeden explores data that demonstrate how the rates of religious attendance align with sexual and reproductive lifestyles, which vary over life histories. Over at least the past half-century in the United States, parents—especially rearing parents and especially those with higher numbers of children—on average have attended religious services more frequently than non-parents. The result is that children are raised in households with relatively high average attendance rates. And yet, over this period, young adults in their 20s have had the lowest attendance rates and population-wide attendance rates have slowly and steadily declined in the United States. Weeden’s chapter uses data from the National Longitudinal Surveys of Youth 1997 and other sources to examine the substantial decline in average religiosity from childhood to young adulthood. He examines how individuals align their religious attendance with their sexual and reproductive lifestyles, leading the large majority of people with religious upbringings to reduce their attendance substantially to the extent they engage in higher levels of sexual activity, drinking/drug usage, and non-marital cohabitation. Overall, the evidence reveals ongoing simultaneous changes in religiosity and reproductive lifestyles, undermining naïve socialization accounts of religious transmission and providing a lifestyle-driven account of religious decline. In Chapter 5, Palmer and Begley hypothesize that religion may be a cultural inheritance mechanism that enables useful survival information to be transmitted from ancestors to their offspring and thereby facilitate reproductive success. Religious traditions often encourage individuals to perform sacrifices and other forms of difficult, painful, or dangerous acts. Costly signaling theory proposes such acts signal to others the actor’s genetic or behavioral quality, thereby influencing receivers to behave toward the actor in ways that increase

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the actor’s inclusive fitness. Costly signaling theory is often combined with sexual selection to explain costly acts performed by males, proposing that these acts influence females to be more likely to mate with the actor. In this chapter, Palmer and Begley explore the limitations of these evolutionary explanations in accounting for many of the costly behaviors encouraged by traditional religions. Examples of sacrifices and other difficult, painful, or dangerous acts regularly encouraged by religious traditions often do not lead to the effect of influencing the behavior of others in ways beneficial to the actor’s inclusive fitness. The acts that do not meet the predictions of costly signaling theory are many, widespread, and enduring, often transmitted for many generations. As such, these cannot be explained away as mere exceptions to the rules, but instead warrant an alternative evolutionary explanation. Palmer and Begley present an alternative explanation to account for these behaviors in the form of the descendant-leaving hypothesis, based on the parental manipulation explanation of altruism, moral elevation, the transmission of traditional behaviors (including religious behaviors), and the importance of measuring evolutionary success over many generations. In Chapter 6, Yael Sela, Todd Shackelford, and James Liddle explore the possibility that religious violence may be a type of mate-guarding strategy. Religion often motivates and exacerbates violence, arguably by being shaped by pre-existing mechanisms in evolved human psychology. First, Sela et al. provide a brief overview of human sexual selection from an evolutionary psychological perspective. Second, they discuss how and why an evolutionary perspective and, in particular, the concepts of intersexual and intrasexual competition may be useful in understanding religiously motivated violence. Third, they present an overview of the research addressing several types of religiously motivated violence, such as mate-guarding and controlling behaviors, wife-beating and uxoricide, “honor” killing, child abuse and filicide, male and female genital mutilation, suicide, group violence and war, and terrorism (including suicide terrorism). They highlight the potential advantages that religiously motivated violence may have provided ancestrally within a sexual selection theoretical framework, and conclude with suggestions for future research. In Chapter 7, Matthew Martinez and Pierre Lienard argue that painful religious rites such as those found in small-scale societies may function as

Introduction

7

costly signals of fitness. Much attention has been given to extraordinarily painful performances featuring religious practitioners deliberately harming themselves in front of audiences. However, there has been no systematic crosscultural study examining the motivations and rationales for such practices. Data from the Human Relation Area Files make apparent the sociological, demographic, and environmental correlates of deliberate painful and public (religious) practices. Typically they are performed in tribal and modern societies of moderate to large sizes, associated with low social mobility, and divided between strong competing coalitional groups. Engaging in such displays affords individuals the means to change others’ perception of the formers’ respectability, resourcefulness, and relevance for particular situations demanding the specific skills advertised in the painful public performances: strength of will, fearlessness, fierceness, resoluteness, and readiness to extreme actions if a situation were to call for it. In Chapter 8, Panagiotis Mitkidis and Gabriel Levy argue that religions—at least the large world religions that dominate the globe today—are attractive to people because they serve as useful “brands” that people can “purchase” as signals of morality. Religions (as such) do not promote morality. They appear to do so because the concept of religion is often associated with morality. Mitkidis and Levy argue that religion gets associated with morality through branding. In the first part of the chapter they review the claim that religion leads to morality or other forms of prosociality. They argue that the experimental evidence backing up that claim is quite weak. Much of the argument centers on what one means by religion, so the authors provide a working definition. The second part of the chapter presents a summary of branding theory and the idea that religion becomes associated with morality through branding. In Chapter 9, David Bell argues that religion helps to facilitate reproductive success by encouraging males to be “dads” (vs. “cads”) and commit to long-term pair-bonding and helping with child-rearing. Despite the social criticisms of modern masculinity, human males are fairly unique among mammals in regard to how strongly invested and committed they are to their children. Even their closely related evolutionary ancestors across the primate families show little resemblance and a remarkable contrast in paternal investment. Most male primates demonstrate little behavioral investment in

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The Attraction of Religion

their offspring. So what happened? Why would homo sapiens evolve so differently from their evolutionary cousins? When did these phylogenetic changes in paternal behavior take place? And towards the purpose of this chapter, could the uniquely human propensity for religion have anything to do with this? In exploring these questions, this chapter provides brief reviews of both the evolutionary foundations of gender and religion. From here, these fields are combined to argue for a network of productive phylogenetic links between paternal behavior and religion. Differences between the genders have been the center of contentious exchanges at least since humans have been recording their thoughts in written language. Contemporary discourse is also dominated by such tension. From the primary material of comedians (the topic of gender is the most frequently used material in stand-up comedy) to the academic and now-popular debates over biological nature vs. social construction, modern society still demonstrates a strong interest in the topic of gender. Moving beyond simple “nature versus nurture” arguments, the conversation has matured towards embracing the complexity of both biological proclivities and cultural constructions that make up contemporary lives in our gendered world. This chapter seeks to advance this discussion, beginning with a review of the evolutionary foundations of fathering and sexual asymmetry, and then moving into the significant role of religion in rewarding paternal investment and stability. Religious rituals are likely a significant factor in disincentivizing short-term sexual strategies and increasing paternal stability and investment. In Chapter 10, Andrew Mahoney argues that although evolutionary explanations for belief in supernatural reality are widespread, there is a lack of investigation as to why people construct elaborate systems of supernatural knowledge (theology) to describe their gods. Investigation is warranted because biologically strategic information, such as tracking the cooperative reputations of potential exchange partners or the reproductive fitness of possible mates, appears to be of greater evolutionary value than memorizing the Qur’an or understanding how to reconcile the doctrines of  anatta  and rebirth. Two prominent theories for the evolution of religion are assessed for their ability to explain theology. Costly signaling theory is unable to account for theology given that one can linguistically misrepresent one’s theological

Introduction

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beliefs, and cognitively optimal theory cannot explain theology given that its maximally counterintuitive content requires considerable effort to acquire. Theology is explained by reconciling these adaptationist and spandrelist accounts of religion. Mahoney argues that religionists who have invested the necessary time and effort to acquire maximally counterintuitive theological knowledge are able to signal this investment by expressing their theologically accurate knowledge base. In the end, the chapters in this volume offer what we believe to be a plausible and empirically supported account of the evolutionary factors involved in religious thought and behavior. Furthermore, the theoretical framework on which these chapters rest offers additional possibilities for research and exploration. Certainly more work needs to be done, but we are optimistic that sexual selection theory, costly signaling, and other evolutionary hypotheses offer fruitful ways to approach explaining large-scale patterns and changes in popular religions across cultures and eras.

1

Why Don’t Abstinence Education Programs Work?(And Other Puzzles): Exploring Causal Variables in Sexual Selectionist Theories of Religion James A. Van Slyke

Religion presents unique challenges as a causal variable for a variety of different forms of social behavior, especially as studied in the psychology and sociology of religion. One of the primary challenges is philosophical. What is the direction of causality? Is religiosity an evolved trait that influences and constrains social behavior or is religious behavior a cultural invention and by-product of other evolutionary adaptations? A second, empirical question is how does religion influence behavior? That is, what mechanism in religion causes changes in behaviors and thoughts in the minds of religious people— including sexual behavior? Historically, many religions contain different laws and norms that purportedly influence sexual choices and relationships. Yet, the empirical data leave many questions unanswered. Do faith-based abstinence programs change adolescent behaviors regarding sexual activity? Do persons make decisions regarding sexual choice and preference independent of any influence from a particular religion? How could such influences be measured? Sexual selection theory and related hypotheses from evolutionary psychology may offer new explanations for the relationship—perhaps causal—between religion and sexuality. Furthermore, the cognitive science of religion, a sub-field of the evolutionary psychology of religion, explores the relationship between different

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The Attraction of Religion

features of human cognition and the formation and function of religion. Much of this research has centered on the cognitive content of religious beliefs such as supernatural agents or the different cognitive mechanisms involved in ritual participation. Sexual selection theory offers the cognitive science of religion a new avenue to explore evolved cognitive tendencies involving mating preferences and strategies and their relationship to religious cognition. Religion escalates particular functions of mating cognition, in that certain features of religion overlap with different functional aspects or goals that support and facilitate long-term mating strategies.

CSR and the Swiss army knife mind The cognitive science of religion (CSR) has eschewed the traditional connection between religious beliefs and behaviors by arguing that evolved cognitive mechanisms play an important role in the formation of religious beliefs, especially at the macro level, not (just) the other way around. In the past 20 years, much of the CSR has been preoccupied with the mental processes involved in the formation of the content of religious beliefs such as gods, ghosts, deceased ancestors, and other types of supernatural agents. The counterintuitive agents hypothesis argues that the types of religious beliefs that get culturally selected for conform to an evolved intuitive ontology that represents and classifies different objects according to specific categories such as person, animal, or artifact (Boyer, 2001). Religious concepts are counterintuitive in that they violate various intuitive expectations of concepts in these categories in particular ways, while maintaining other parts of the basic categorical assumptions. Thus, a ghost is a cognitive representation based on the category template for “person,” but violates the category’s expectations about “person” by being able to move through walls. According to many cognitive scientists of religion, the prevalence of such supernatural agents in religions is thought to be a by-product of the human tendency towards agency-based explanations of the world and its working (Barrett, 2004; Boyer, 2001; Guthrie, 1993). Children intuitively prefer explanations of happenings based on agents at work in the world, and traces of this cognitive tendency continue through to adulthood (Barrett & Keil, 1996;



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Kelemen, 2004). Religious rituals have also been explored in terms of their exploitation of action representation systems that process ritual behaviors in terms of agents, the ritual action performed, and the objects used during the ritual (Lawson & McCauley, 1990). Others have explored religious rituals based on different memory systems that favor either a “doctrinal mode” of encoding experiences in memory, based on repetition during rituals, or an “imagistic mode” of encoding experiences in memory, based on high emotional arousal during rituals such as in stressful initiation rites (Whitehouse, 2004). Sexual selection theory offers a new set of hypotheses to help analyze religion by investigating the role of evolved mating strategies. Sexual selection theory provides an extension of the CSR’s roots in evolutionary psychology, in that mating preference is another type of cognitive adaptation that works alongside cognitive biases regarding agency, intuitive ontology, and action representation. Presumably, sexual selection has played such a ubiquitous and important role in human evolution that it must have some relationship to religious cognition as well. Tooby and Cosmides originally suggested the Swiss army knife view of human cognition, which argued that much of human behavior and thought is highly unconscious and processed according to different cognitive tools that were advantageous for our evolutionary ancestors (Cosmides & Tooby, 1995). Thus, part of human social cognition consists of adaptations for mate attraction and selection, which suggests possible interactions between mating cognition and the functions of religion. McCauley’s distinction between the cognitive processing of information that is natural or unnatural provides a helpful way of conceptualizing the role of human evolution in human cognitive processing (McCauley, 2011). McCauley argues that some types of information are easier to process and cause the deployment of several different types of intuitions about particular domains. For example, social situations trigger numerous intuitions about what other people may be thinking or intending based on our capacity for a theory of mind and other cognitive programs associated with social cognition. In contrast, as McCauley notes, much of advanced scientific explanations are based on processing information in ways very alien to natural features of human cognition. That is, science often produces results that are highly counterintuitive to our default cognitive expectations about the world.

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The Attraction of Religion

A helpful example is the difference between teaching about mate preferences in evolutionary psychology and z scores in introductory statistics. Ask a classroom of men and women to form groups and discuss what they find attractive in a potential mate and they will quickly generate lists of different features often with reoccurring themes and values. In contrast, the very same first-year students exposed to a basic statistical concept such as a z score are often dumbfounded and have difficulty understanding the concept except through repeated instruction and rote memorization (Garfield & Ahlgren, 1988). Thus, evolution has formed human cognition to recognize, process, and understand certain types of information quicker, easier, and more efficiently than other types of information and supplies more intuitions and hunches about possible descriptions in particular domains in contrast to others, especially domains that were relevant to evolution in terms of adaptive fitness. Mating behavior is one of those domains in which people have a relatively easy time processing and producing intuitions, perceptions, and observations (e.g. about different preferences in potential mates). This does not suggest that these preferences are determinative of mating behaviors or choices, nor does it suggest that these perceptions are accurate. In fact, most persons who have fallen in love in their lifetime recognize the amount of misperception and irrationality that often persists in various forms of human mating (Fisher, 1994). Thus, human cognition related to mating is relatively easy, quick, and often unconscious, and thus can be said to be “natural.” The evolution of human cognition involved different cognitive programs that assess mate value and generate mating strategies based on a variety of features that lead to successful mate attraction and copulation in our collective evolutionary past.

Religion as a variable Identifying how religion influences behavior, let alone defining religion, spirituality, or other contested terms, continues to present several challenges in the psychology of religion and related fields. One possibility is that religious cognition has a direct influence on behavior. That is, as people learn particular religious beliefs and values, their behavior becomes more consistent with



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their internalized beliefs. This certainly is the case in some contexts, but other research has demonstrated a disconnection between assumed religious beliefs and corresponding actions. Probably the most famous study that questioned this relationship was the Princeton study where a young priest was crossing the campus to deliver a sermon on the Good Samaritan (Darley & Batson, 1973). The parable of the Good Samaritan is a biblical story about a man who helps another man injured and stranded on the roadside whom everyone else ignores and does not stop to help (Lk. 10.29–37). The researchers placed a struggling man on the sidewalk in the path of the priest as he was walking to deliver this sermon, which seemed to present a situation that simulated the moral dilemma of the story. Going to deliver a story on the Good Samaritan would presumably activate the religious cognition associated with helping behaviors towards others, but the primary causal variable that influenced the helping behavior was how rushed the priest was to get to the location of his sermon. Of all the participants in the study only 40 percent actually helped the stranded man, and their behavior varied according to time constraints, with 63 percent helping when not hurried but only 10 percent helping in the high-hurried condition. Thus, the study seems to demonstrate that situational and contextual variables have a stronger influence on helping behavior in contrast to internalized religious beliefs. Although summing up the priest’s moral character based on one individual instance is problematic, it still demonstrates that there is not a simple causal relationship from religious belief to behavior. This creates a problem for assessing the relative role of religion on behavior in general. Some have suggested that religious beliefs are primarily a by-product of cognitive adaptations, thus religious beliefs arise in human culture as a secondary effect of cognitive adaptations designed for other evolutionary benefits, while others argue that religion serves an adaptive function in terms of costly signaling and social cohesion—or perhaps it is a bit of both (Atran & Henrich, 2010; Boyer, 2005; Sosis, 2009). My suggestion here is that mating strategies can produce certain biases that promote attachment to particular religious beliefs, values, and social arrangements based on their relationship to the strategy currently being pursued. Religious beliefs have an influence on human sexuality by activating mating cognition

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The Attraction of Religion

and the corresponding behaviors associated with a particular strategy. This doesn’t necessitate the reduction of religious cognition to mating cognition, but demonstrates the complex relationship between multiple causal variables involved in human cognition and religion (Van Slyke, 2011).

Mating strategies One way to distinguish mating strategies is to classify them as either shortterm or long-term. According to the General Social Survey (GSS), most Americans are split in terms of these two types of strategies. In 2006, of the Americans surveyed in their 40s and 50s, a third had only one or two sexual partners since age 18, while another third had 10 or more; 37 percent were in a first marriage and 46 percent had been through a divorce; 21 percent had no children while 31 percent had three or more (Smith et al., 2013; Weeden et al., 2008). This is not a hard-and-fast distinction in that many tactics, or individual mating behaviors, may fall in between these two categories and persons may adopt different strategies based on a variety of factors (Buss & Schmitt, 1993). Basic sexual anatomical differences suggest that males should engage more frequently in short-term strategies in comparison to females simply based on parental investment (Trivers, 1972). However, recent theories also suggest that females may engage in dual mating strategies and the simple dichotomy between short-term and long-term mating strategies, as applied to males vs. females, may be misguided (Pillsworth & Haselton, 2006b). Engaging in short-term vs. long-term strategies provides different types of benefits as well as drawbacks. The primary benefit for males in pursuing a short-term strategy is an increase in the number of potential successful copulations; males have a relatively low investment in the copulation act, thus, this allows for a higher frequency of potential mating with other females (Buss & Schmitt, 1993). Additionally, short-term strategies primarily favor indicators of good genes in the opposite sex to maximize the individual fitness of potential offspring. Evolved indicators of good genes based in short-term strategies are based primarily on physical cues in potential partners. Numerous studies indicate a variety of features males typically prefer in females such as full lips, clear skin, long hair, muscle



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tone, facial symmetry, body symmetry, low waist-to-hip ratio, and feminine voice (Buss, 2006). Many of these cues perform a double duty as both an indicator of good genes as well as indicators of youth, which increases the likelihood that potential female partners are currently within their reproductive window. For females, short-term strategies may often take the form of extra-pair copulations (EPC), where the female is currently engaged in a long-term strategy with one partner, but may seek other short-term partners based on a variety of factors. Female mating preferences change throughout their menstrual cycle based on their current level of fertility (Pillsworth & Haselton, 2006a). During the high-fertility phase of the menstrual cycle (late follicular and ovulatory) females show a preference for several different types of attributes in males including more masculine faces, more masculine voices, the scent associated with men with more symmetrical faces, and displays of dominance and competition (Gangestad et al., 2004; Gangestad & Thornhill, 1998; Penton-Voak & Perrett, 2000; Puts, 2005). These traits would primarily be indicators of genetic fitness, thus females are willing to risk long-term strategies based on an unconscious assessment of potential gains in the genetic race. Several mate-guarding tactics have evolved in males to counter these strategies, such as being more attentive, spoiling, and monopolizing, as well as displaying increased levels of jealously and being more possessive (Gangestad et al., 2002; Haselton & Gangestad, 2006). One of the interesting empirical questions is whether males can actually detect ovulation, since it has been commonly assumed that estrus is concealed in the human species (Burt, 1992). Recent evidence suggests that males may be able to detect when females are in the high-fertility phase of their cycles. Males rated a woman’s body scent as most attractive during the timeframe closest to ovulation, increased their mate retention tactics closer to the time of ovulation for their current partners, and male levels of testosterone increase when exposed to the scent of an ovulating female (Gangestad et al., 2002; Haselton & Gangestad, 2006; Kuukasjarvi et al., 2004; Miller & Maner, 2010). Long-term strategies typically focus on rearing children and are usually favored by females because of the considerable parental investment necessary for females to even carry a child to term (Trivers, 1972). For females, the

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The Attraction of Religion

primary objectives are securing resources for themselves and their offspring as well as seeking a mate interested in partnering regarding parental duties. Females tend to favor potential long-term partners who: (1) have the ability and willingness to offer resources to her and her children; (2) have the ability to physically protect her and her children; (3) show promise as a good parent; and (4) show compatibility regarding goals and values and investment in a long-term strategy (Buss, 2003). A cross-cultural study of over 10,000 participants showed that females desired male partners who were “good financial prospects” and sought qualities associated with resource acquisition such as ambition, industriousness, and social status (Buss, 1989). Males enter into long-term strategies for different reasons. Long-term pair-bonding increases within-pair fertility as well as paternity certainty by allowing males better opportunities to monitor and possibility restrict the actions of their partners. Females have direct access to and can easily assess the genetic relatedness of their progeny, while males do not have any straightforward means for knowing whether the female’s progeny is actually his own. This increases male sensitivity to paternity cues and may also increase mate-guarding and jealousy. Male jealousy is much stronger in the context of potential extra-pair copulations in comparison to females, who show a much stronger reaction to potential emotional commitments to other females (Buss, et al., 1992). Males tend to be better at inferring possible EPCs in their partners in contrast to females and were more likely to make false positive errors about their partners (Andrews et al., 2008). Significant research has outlined the parameters of long- vs. short-term mating strategies. The relationship between these strategies and religion is less clear and, in fact, the relationship between religion and sexual behavior in general is highly complicated. The next section will discuss the relationship between religion and sexual behaviors by exploring empirical data that often demonstrates mixed results regarding the role of religion in constraining or modifying sexual behavior. Several studies demonstrate the difficulties in assigning a causal role for religion in sexual behavior, especially in regard to abstinence-based programs. However, other avenues of research show that religion does seem to have some kind of effect on certain kinds of sexual behavior. The thesis of this chapter is that religion acts as a causal variable when it activates mating cognition associated with a particular mating strategy.



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Religion and mating behavior One of the important questions regarding the role of religion and mating cognition is whether religion is primarily related to short-term or long-term strategies. Weeden, Cohen, and Kenrick make a strong case that one of the primary functions of religion in the United States is to support persons pursing long-term mating strategies (Weeden et al., 2008). Males pursuing long-term strategies forgo the short-term strategy of multiple partners in favor of higher fertility based on increased copulations with a single female as well as increased paternity certainty and fidelity based on a single monogamous relationship. Females forgo “better genes” from possible short-term partners in favor of a long-term strategy with potential gains in commitment of economic resources and parental investment as well as pledges of sexual fidelity. In a survey of over 21,000 United States residents (average age 44.6) from the GSS survey, endorsement of sexual behaviors consistent with a long-term strategy were the strongest correlates with church attendance (Weeden et al., 2008). Among an undergraduate sample of 902 students (average age 19.2) from several areas of the United States, attitudes toward sexuality and family consistent with a long-term strategy were the strongest correlates with church attendance. Sexual behaviors associated with long-term strategies included number of sexual partners, desire for a family, and initiation of divorce. Attitudes regarding sexual behavior were the strongest correlates in comparison to a wide range of moral beliefs including drug use, lying, and forgiveness. The reproductive religiosity model suggests a causal relationship from mating strategy to religious affiliation, in that persons gravitate towards or stay involved in religious institutions to help facilitate their mating strategy based on the strong correlation between sexual morals and religious attendance. Many religious institutions and groups commit a considerable amount of resources to support monogamous married relationships such as marriage retreats, family life education programs and teachings regarding marital fidelity. Conservative Christian organizations such as Promise Keepers are explicitly committed to promoting values associated with long-term strategies including sexual fidelity and parental investment from fathers in the forms of economic and emotional investment (www.promisekeepers.org).

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The Attraction of Religion

This relationship between long-term strategies and religion is not limited to Western societies. Among the Dogon of Mali in West Africa, religious menstrual taboos are associated with the usage of “menstrual huts” where women are exiled to designated areas of the group during their time of menstruation (Strassman et al., 2012). The indigenous religions conceive of menstruation as a type of pollution that acts as a form of supernatural monitoring over the reproductive cycles of the women, which promotes reliable signaling of menses. Strassman et al. argue that this religious belief and associated ritual segregation of the women acts as a defense against cuckoldry. The practice produces a significantly lower rate of DNA mismatches between father and son pairs in comparison to other religious affiliations from surrounding tribes in the area.

Abstinence-only programs Early initiation into sexual activity among adolescents has been correlated with a number of problematic behaviors including sexual risk-taking, pregnancy, and sexually transmitted diseases (Kirby, 2007; Sandfort, et al., 2008). Several religious institutions have attempted to develop sexually restrictive programs to help encourage abstinence among teenagers. Websites such as True Love Waits and Christian Family Planning attempt to promote the abstinence message on the internet and contain materials for churches and other organizations to use in youth groups (www.truelovewaits.com; www. christianfamilyplanning.net). Programs such as these have had mixed results. In an analysis of selfreport data in thirteen abstinence-only programs in the United States, no program affected the incidence of unprotected vaginal sex, number of sex partners, condom use, or sexual initiation (Underhill et al., 2007). In an analysis of four United States Title V funded abstinence-only programs, no program had an impact on the rates of sexual abstinence (Trenholm et al., 2007). One longitudinal study of teenagers under 15 years of age in 1996 matched 289 abstinence pledgers with 645 non-pledgers. When surveyed again in 2001, 82 percent of the pledgers denied ever having made the pledge and there was no difference between the groups regarding premarital sex, sexually transmitted diseases, and anal or oral sex variables. One study



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of 662 African American students from an urban context did find that abstinence-only programs reduced sexual initiation (33 percent reported engagement in sexual activity) in comparison to a comprehensive sexual education program (48.5 percent reported engagement in sexual activity) (Jemmott et al., 2010). However, the abstinence-only program did not affect condom use. If religion is associated with long-term strategies for mating, then why don’t abstinence-only programs seem to work? A possible interpretation is that the youth in the abstinence-only programs may not be engaged in long-term strategies, but their parents want them to be. Parents, religious leaders, and government officials already engaged (or wanting to appear to be engaged) in a long-term strategy often promote abstinence-only programs, but this may not be the strategy currently employed by the adolescents in their programs. There is often a strong discrepancy in attitudes about sexual behavior between parents and their adolescent children. Secondly, according to the reproductive religiosity model, the mating strategy is the causal variable that leads to affiliation with a particular religion. Abstinence-only programs are often trying to initiate adolescents into features of a long-term mating strategy. Thus, religion may not have as strong an effect on generating the pursuit of a particular mating strategy or, because of their age, adolescents may still be simply exploring both short-term and long-term strategies as different options.

Religiosity and short-term vs. long-term strategies The mixed results regarding abstinence-only programs are not necessarily generalizable to the impact different types of religiosity may have on sexual behavior. A case study of Christian youth in the Wakiso district in Uganda demonstrated an association between higher levels of religiosity (measured based on self-report data of participation in religious practices such as prayer and expressing thankfulness to God) and lower levels of HIV infection (Kagimu et al., 2012). This same effect was demonstrated among a group of African American adolescents in urban areas of Atlanta, Georgia in the United States. Higher levels of religiosity were associated with lower risk behaviors regarding HIV infection (Elifson et al., 2003). A

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The Attraction of Religion

separate study also showed that adolescents who scored high on religiosity scales were more forthcoming with their partners regarding sexual activity (i.e. HIV and pregnancy prevention) and avoided risky sexual encounters (McCree et al., 2003). Similar results were found among a sample of adolescents and young women (age range 13–21) in the Pittsburgh, Pennsylvania area. Higher levels of religiosity were associated with lower rates of sexual intercourse, STDS, pregnancies, and fewer sexual partners (Gold et al., 2010). These studies suggest that religiosity may increase behaviors and attitudes associated with a more sexually restrictive, long-term strategy and decrease behaviors and attitudes associated with a more sexually unrestrictive, shortterm strategy. One of the primary complications of engaging in a long-term strategy is the presence of others engaged in a short-term strategy, which may quickly reduce the effectiveness and returns of the strategy. Sexual selection theory suggests that males engaged in a short-term strategy will often use different types of behaviors to advertise genetic fitness, including risk-taking, aggression, and displays of physical strength (Archer, 2009). The potential fitness gains associated with these types of strategies in males often lead to increases in impulsivity and discounting of future rewards (Wilson & Daly, 2004). Males often demonstrate higher levels of discounting for future rewards. For examples, pictures of attractive opposite-sex individuals increase men’s impulsivity, the mere presence of opposite-sex individuals increases risktaking, and males often demonstrate higher levels of discounting regarding monetary rewards (Kirby & Marakovic, 1996; Palowski et al., 2008; Wilson & Daly, 2004). In a recent set of experiments, McCullough and his colleagues speculated that religious cognition should down-regulate factors associated with shortterm strategies to help in the promotion of long-term strategies (McCullough et al., 2012). For the first experiment, college students were recruited and then separated into three different conditions. In the religious condition, religious cognition was activated by each of the participants writing an essay about their feelings about God and their religion. Nonreligious students wrote about their skepticism or general feelings about religion. For the two other conditions participants either described their feelings about their country (secular condition) or described belongings in their home (control condition). All



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participants then completed a Monetary Choice Questionnaire (MCQ), which assessed their discounting of future rewards. Interestingly, the only significant difference between groups was found between males in the religious condition and both the secular and control condition, with the lowest rates for discounting future rewards occurring in the religious condition. The same trend occurred in experiments two and three. In experiment three, religious cognition was activated/non-activated by reading articles that provided scientific evidence for the existence of the afterlife (religious condition) or scientific evidence against the existence of the afterlife (nonreligious condition). The MCQ was again administered to all groups, but there was a significant difference between the religious and nonreligious conditions for men only, with significantly less discounting among the religious group. In the third and final experiment, religious priming was used through working on scrambled sentences which contained religious words such as “spirit” or “God” in the religious condition, but were absent in the nonreligious condition. This same method of priming has been used in experiments on religiosity and pro-sociality (Shariff & Norenzayan, 2007). In this experiment, however, the dependent variable was measured using a handgrip task as a measure of physical endurance, which served as a proxy for displays of physical strength. Religious primes significantly decreased the grip strength measures in males in comparison to the nonreligious primes. For women there were no statistically significant differences. The latter study offers several important insights. First, in all three experiments, there were no real differences between females in the different conditions, which suggests that these types of display are not a general part of female mating cognition. Secondly, the personal religious affiliation of the males did not change the effectiveness of the religious conditions on the dependent variables. Whether they were personally religious or not, activating religious cognition still affected cognition associated with shortterm strategies. This demonstrates the possibility that personal belief in God or a particular religion is not necessary for religion to have an influence on mating cognition. Thus, religious cognition may decrease behaviors and cognition associated with short-term strategies in order to facilitate a long-term strategy.

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The Attraction of Religion

A second set of experiments also demonstrates an interesting relationship between mating strategies and levels of religiosity (Li et al., 2010). In these experiments, participants increased their levels of religiosity in response to other attractive mating competitors, presumably to engage in a long-term strategy in response to a larger pool of short-term competitors. In experiment 1, university students (n = 269, 97 men, 172 women) viewed dating profiles of either 6 attractive females or 6 attractive males and then filled out a questionnaire regarding personal religiosity (i.e. “I believe in God,” “religious beliefs are important to me in everyday decisions”) (Li et al., 2010). Interestingly, religiosity scores increased, for both men and women, in the presence of attractive persons of the same sex. That is, women demonstrated an increase on scores of self-reported religiosity in the presence of attractive females while men demonstrated an increase on scores of self-reported religiosity in the presence of attractive males. The second experiment added a control group, but the findings from the first experiment were replicated with another sample of university students (n = 184, 106 men, 78 women). Li et al. (2010) suggest that religiosity may fluctuate based on ecological contexts, especially regarding potential mating strategies. For example, if there is an abundance of females in a mating pool, some archival data suggests that males may engage in more short-term strategies and exposure to attractive members of one’s own sex actually decreases self-evaluations of competitiveness within the mating pool (Gutierres et al., 1999; Guttentag & Secord, 1983). This effect is seen in the fluctuating religiosity among the participants in the experiments, such that the presence of attractive mating competitors caused a change in strategy from short-term to long-term. The detection of several attractive competitors poses difficulties for a short-term strategy, so a long-term strategy is adopted with the corresponding increases in levels of religiosity for potential advertisement. This interpretation is supported by research that demonstrates that religion may serve as a type of ecological niche that persons move in and out of depending on their goals (Storm & Wilson, 2009).



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Religiosity and group-level effects In addition to activating long-term strategies at the individual level, religious cognition may also activate these strategies at the group level as well. Recently, Henrich, Boyd, & Richerson (2012) have argued that the prevalence of monogamous marriage in industrial/Western countries may be the result of an overall benefit to the group during cultural evolution that solved certain social problems associated with an overabundance of single unmarried males. Sexual selection theory would seem to suggest that the large differential in income that continues to rise across the industrialized world would favor more polygynous marriage arrangements. Historically, the widening of the gap in overall wealth between males of higher and lower socioeconomic status would often lead to the wealthiest men attracting the largest number of mates (Betzig, 1982). But this does not seem to be the case today, where monogamous marriage arrangements dominate much of the Western world. Henrich et al. (2012) suggest that the prevalence of monogamous marriages decreases the overall pool of single unmarried men and reduces intrasexual competition and corresponding crimes such as rape, murder, assault, and robbery. When intrasexual competition increases and the pool of potential mates decreases, males will often turn to more short-term sexual strategies that are more aggressive and highly discounting of future consequences. This creates a highly unstable social context that is an overall detriment to intergroup competition for various resources. The gap between one potential mate and zero potential mates, in terms of reproductive success, is quite large. Thus, groups that promote larger pools of males to have access to at least one mate significantly decreases the adverse effects of single unpaired males and increases positive societal effects such as overall income and parental investment. Unmarried men are more likely to engage in violent crime, rape, and robbery, as well as higher levels of substance abuse and gambling (Daly & Wilson, 1990; Thornhill & Thornhill, 1983). In contrast, marriage reduces the rates of crime (by 35 percent and up to 50 percent for violent and property crime) as well as the overall rates of drug and alcohol use, which are commonly associated with various crimes (Duncan et al., 2006; Sampson et al., 2006). Comparisons between countries that have higher vs. lower rates of polygyny demonstrate that higher rates of polygyny

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The Attraction of Religion

are associated with lower GDP and lower rates of both infant and child mortality (Tertilt, 2006). The role of monogamy in inter-group competition suggests an interesting role for religion in fostering this cultural adaptation. Religious cognition activates behaviors associated with a long-term strategy, increasing the effectiveness of monogamy in a society, while also decreasing potential social risk factors that threaten potential group benefits. In addition, in certain contexts, religion also has an effect on several societal ills commonly associated with a higher pool of unmarried single males. Although it is a contested area of research, there is evidence that religiosity may decrease levels of criminality and delinquency (Johnson et al., 2000). Faith-based organizations and religious communities play an important role in certain types of criminal rehabilitation and prevention in at-risk communities (Johnson, 2011). A meta-analysis of several studies of this relationship showed that religiosity is associated with lower levels of crime and has an even stronger association with lower levels of drug use and gambling (Baier & Wright, 2001). McCullough and Willoughby (2009) demonstrated a strong relationship between religiosity, self-regulation, and self-control for a variety of social behaviors, which may be another key to the role of religious cognition in promoting positive social behavior as well as monogamous relationships. A meta-analysis of over 12 studies demonstrated that religious adults are more likely to stay married and have higher levels of marital satisfaction (Mahoney et al., 2001). Religious individuals often view marriage as “something more”: more than the self, more than the couple, and more than the family unit (Dollahite et al., 2012). Viewing marriage as something that has divine or transcendent value may be part of the reason for the increases in marital longevity and overall satisfaction. When couples viewed marriage as religious or sacred and integrated their marriage lives with this religious belief, there was an association with greater global marital adjustment, higher levels of perceived benefits from the marriage, decreased levels of conflict, more verbal communication, and less verbal aggression (Mahoney et al., 1999). The effects of this form of “sanctification” appear to be possible for marriages based on both theistic and non-theistic beliefs (Mahoney et al., 2009).



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Conclusion Sexual selection theory presents several interesting hypotheses that may help us to more fully understand the role of religion as a potential causal variable in human social behavior. Although cognitive scientists of religion have focused on other facets of evolved human psychology, mating preferences and choices offer new facets of cognition that may have an effect on religious values and beliefs—and vice versa. Mating cognition and religion pose an interesting relationship in that there may be an overlap between religious beliefs and values in particular faith traditions and the adaptive functions and goals of a long-term mating strategy. Several experimental studies demonstrate this effect both as a variable for individual mating cognition and as an aggregated variable at the level of a group cultural adaptation. Thus, religion may act as a causal variable in human cognition and behavior as it activates a suite of preferences and biases associated with long-term mating strategies.

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Religion and Parental Cooperation: An Empirical Test of Slone’s Sexual Signaling Model Joseph Bulbulia, John H. Shaver, Lara M. Greaves, Richard Sosis, and Chris G. Sibley

Sexual signaling theory posits that religions evolved, at least in part, to support mate discrimination (Slone, 2008). According to this theory, potential mates attend to religious expressions to assess each other’s qualities. As such, sexual signaling models of religion are a sub-group of commitment signaling models of religion, which hold that religious expressions function to identify traits relevant to assessing partner qualities, quite generally (Irons, 2001a; Mahoney, 2008; Sosis, 2003; Sosis & Bulbulia, 2011).1 That is, sex is a special case of a cooperation dilemma because the interests of potential mates do not perfectly overlap. The dilemma is fundamental to all human life. Offspring link parents to a common genetic fate. Though sex is one of many collaborative interactions, from a gene’s eye view, it is ultimate. Given this importance, and knowing nothing else, we might expect religion to evolve, at least in part, to facilitate mate discrimination. What evidence might enable us to test the predictions of sexual signaling models of religion? Sexual signaling theory posits that human males and females have different reproductive potentials, and for this reason, that males and females ought to differentially value the traits of prospective mates. Sex differences in religious behaviors associated with mate-evaluation can thus be used to test predictions derived from the sexual signaling theory. Regarding religion, if certain religious expressions are associated with qualities that are differentially valued by females, we might expect men to express such behaviors more frequently

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than women. By the same token, if certain religious expressions are associated with qualities that are differentially valued by males, we might expect women to express such behaviors more frequently than men. Sexual signaling can be assessed without knowledge of the mechanisms that underpin different expressions. In humans, such mechanisms are likely to involve complex dependencies between genetic endowment, cultural endowment, and life experiences. Nevertheless we can obtain initial evidence for sexual signaling models of religion by focusing on sex differences in behavior, and by assessing the associations of signaling behaviors (prayer, church attendance) with fertility. The present study examines two cooperative traits relevant to human mating: fidelity and social reputation, and investigates the links between religious behaviors that identify these traits and their association with fertility.

Fidelity and social reputation Infidelity can lead to resource loss for both men and women. Yet for men the risk is much greater; female infidelity can lead to males unwittingly investing in children sired by other men. The biology of birth assures accurate assessment of maternity. However, males risk cuckoldry (Low, 2001).2 Though male infidelity exposes women to the potential diversion of resources towards other women/unrelated offspring, life-history theory (e.g., Hill & Kaplan, 1999) predicts that males will be more interested in the sexual infidelity of the opposite sex than females (holding social and ecological differences equal).3 Among humans, divisions of labor involve complex and extensive, direct and indirect reciprocity with non-kin. This includes, among other things: bush craft, collective defense, construction, education, foraging, hunting, long-distance trade, and tool-making (Alexander, 1987; Sterelny, 2011). It has been claimed that children remain mainly dependent on this cooperation for nearly two decades after birth (Gurven & Walker, 2006) and that parents require support from the wider social group when providing for offspring (Kaplan et al., 2000).4 It is not enough to judge whether a potential mate has resources, but also whether a mate can draw resources from others, including unrelated exchange partners.



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Social reputation gradients are thought to enable predictable help from non-kin through a kind of image-scoring: people who demonstrate commitment and utility to a social group are accorded greater social prestige (Nowak & Sigmund, 1998). Individuals within a social network tend to trade with those who reliably exhibit prestige, and they avoid those with low or uncertain prestige (Henrich & Gil-White, 2001). Put simply, social prestige is a form of social capital. Focusing on the mating dilemma, it would appear that mates who are able to display high social prestige will thereby convey information about a core resource relevant to the success of potential offspring, namely an ability to marshal help from others in a community. Though both males and females are expected to signal prestige to potential and current mates, sex differences in the relative importance of social reputation are thought to arise from differences in reproductive potential, and become manifest in divisions of labor and economic stratification. It is theorized that across most of human history, men have tended to engage in high-risk cooperation with unrelated men in areas such as big-game hunting, defense, military expansion, and inter-group economic trade, whereas female cooperation in foraging and provisioning has tended to occur through repeated interactions with familiar and typically genetically related women (Bliege-Bird et al., 2001; Byrne et al., 1989; Fessler, 2002; Gurven & Hill, 2009). For this reason, evolutionary theorists conjecture that female interest in male social reputation tends to be more valued as a mating signal than male interest in female social reputation (Pillsworth, 2008). Again, our present interest is in whether men signal their social-network reputations more frequently than women, on average and holding all else constant.

Theoretical predictions To assess the predictions of sexual signaling on fidelity (attribute 1) and social reputation (attribute 2), it is first necessary to assess which religious expressions might be associated with fidelity and which religious expressions might be associated with social-network reputation. This task amounts to a problem of signal identification. Having identified and measured religious expressions that people may employ, it is then necessary to assess whether

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men and women differ in their average expression of such signals. This second task amounts to a problem of model evaluation. A secular country provides a good test because its religious residents have readily available the alternatives for assessing mate quality. Such alternatives might be expected to dilute the relevance of religious behavior to mate-evaluation (Hoverd et al., 2012). Our study was conducted in New Zealand, a largely secular country with many residents who do not identify with any particular religion (Wilson et al., 2013). Indeed, analysis of census trends shows a gradual and steady decline in Christian affiliation in New Zealand over the last 40 years (Hoverd, Bulbulia, Partow, & Sibley, in press).

Signal identification: Prayer will be associated with fidelity, as indicated by greater belief in God We could not assess fidelity directly using our survey data because the study does not ask participants about whether they were faithful (this would arguably be very hard to assess reliably using self-report data). However, previous research indicates that belief in God, when recollected or primed, is positively associated with pro-normative behavior and restraint from acting in self-interest (Norenzayan & Shariff, 2008). Belief in God is also associated with greater self-regulation and inhibition (McCullough & Willoughby, 2009). Recent neurological studies show that frequency of personal prayer— whether repeated and ritualistic or private and improvisational—is positively associated with greater belief in God (Bulbulia & Schjoedt, 2010; Schjoedt et al., 2009). Given past evidence for the relationship between reminders of God and self-restraint, we argue that the frequency of prayer may function as a signal of fidelity. (Note: signals do not need to be infallible to evolve as cooperative signals [Bulbulia, 2004]).

Signal identification: Church attendance will be associated with greater social capital, as indicated by stronger religious ingroup commitments Previous research suggests that church attendance is associated with religious ingroup reputation. By “church attendance” we include attendance at any



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public religious service such as a temple, mosque, or synagogue. The motivations for the predicted relationship between church attendance and religious ingroup reputation were both theoretically and empirically motivated. First, drawing on a large American sample (n = 21,131), Weeden and colleagues found that the best predictor of church attendance is (restrained) sexual behavior (Weeden et al., 2008). The authors found an association between sexual behaviors and sexual mores in a sample of (n = 902) American university students. Though we would caution against inference to the larger American population based on this university sub-sample (as this ignores multilevel dependencies of the data), the behavioral measures in the study were nevertheless consistent with a model in which people use church to obtain social capital and display virtue. Second, postulated reputation enhancements from church attendance have received empirical support from cross-cultural studies. For example, Shaver (2012) reported that in Fiji, church attendance was associated with greater social standing and a reputation for being a cooperator. Third, we note that church attendance in New Zealand occurs in public settings among groups of mainly unrelated individuals. Put simply, going to church is an act that may be witnessed by a broader social network than one’s family. Signaling theorists argue that drawing attention to the expected audiences of religious practices helps to distinguish different types of functionality in religious signaling (Bulbulia & Sosis, 2011; Sosis, 2009). From a theoretical perspective, then, church attendance should be an ideal vehicle for expressing one’s cooperative commitments to a religious social network, and as such, for receiving reputation enhancements. The present study asks the question: why might church attendance in New Zealand function as an honest signal of one’s cooperative commitments to a religious social network? That is, we expect from previous studies that church-going is associated with reputation enhancement. We expect that this reputation enhancement is related to the time and resources invested in a group. However the present study sought to deepen the explanation for why religious attendance is linked to reputation enhancement by tracking psychological variables associated with religious ingroup commitment. Irons (2008) proposes that religious behaviors function as honest cooperation signals because the subjective value of religious behaviors is conditional

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upon the acceptance of values that would otherwise appear, to use Irons’s terminology, “crazy.” That is, it is more difficult to go to church if one lacks commitments to a religious group. In terms of the present study, Irons’s model predicts that, in addition to identifying commitments to a moralizing God (who sanctions social-network cooperation and who sanctions fidelity), church attendance should also identify values about the special entitlement of one’s own religious group. By contrast, we did not expect to find religious group commitments associated with prayer frequency. To identify religious ingroup values we capitalized on a novel measure assessing religious ingroup entitlement attitudes administered as part of the New Zealand Attitudes and Values Study (NZAVS; see below: Method). The measure assessed the degree to which participants believed their own religious group is deserving of special recognition and benefit. Importantly, the measure should not be taken as an indicator of out-group hostility. An analogy might help to understand the key distinction between within-group pride and out-group prejudice. Several of the authors of the present study are strong Pittsburgh Steelers fans. We think this team is better than all others in the history of the sport. However we do not bear other US football teams any animosity. And it is possible (we think probable) that our judgment is correct. Ingroup commitment taps into the value one places on one’s own religious group as special. That’s all. The measure does not specifically ask about ingroup values in relation to other religious groups. To summarize, the traits associated with church attendance remain poorly understood, quite generally. Signaling theory postulates that some of this variance will be explained by religious ingroup commitment. Our novel religious ingroup entitlement scale tapped into the strength of these commitments by asking participants to identify whether their religious group is especially deserving of esteem over all other religious groups.

Model evaluation: Religiously identified women pray more frequently than religiously identified men Conditional on the validity of the hypothesized association between prayer rate and strength of commitment to God, we predicted that religious women should pray more frequently than religious men.



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Model evaluation: Religiously identified men will attend church more frequently than religiously identified women Conditional on the predicted association between church attendance and strength of both belief in God and religious ingroup entitlement values, we hypothesized that men should express greater social-network commitments by attending church more frequently than women.

Among religiously identified New Zealanders, prayer and church attendance will be associated with greater fertility Sexual selection theory, then, makes quite specific predictions about differences in fertility effects associated with prayer and church attendance within the religious population. Recall that prayer is expressed within family settings, among those who have already succeeded in attracting mates—the potential/ current mates are already at intimate range. In cross-sectional datasets such as ours, we would expect the effects of praying as a signal of sexual fidelity to manifest in greater fertility among the population of women who pray frequently, as well as a lower probability of having zero children. This is because, within the religious population, women who have been successful at signaling their commitment and fidelity should have been more likely to reproduce relative to women who have been less successful at signaling their commitment and fidelity. Slone’s model also predicts differences in the composition of frequent church attendees. We have argued that church is a forum in which people express their cooperative virtues to a wider social network. Slone points out that among those lacking mates, this broader network consists of potential, but as yet unfamiliar, mates (Slone, 2008). Hence, according to Slone’s model, church not only functions as a venue to display social commitment and receive social prestige, but also functions as a setting for attracting new mates. Hence, Slone’s model predicts a mixed population among frequent churchgoers: those who have succeeded in reproducing and remain committed to the religious group, as well as those who wish to display the magnitude of their religious commitments to potential mates. That is, the congregation of a given church should consist of a population of successful breeders alongside of a population of lonely hearts. In a

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cross-sectional dataset such as ours, we would expect the predicted mixed population of frequent church-goers to consist of one group that has greater overall expected children and another that has a higher overall probability of having zero children at that point in time (but perhaps hoping to have many children in the future). We can assess this prediction in the context of zeroinflated regression models by modeling zero-inflation as a deviation from expected fertility while adjusting for and assessing the variances of denominations (see Method).

Results Correlation of variables Bivariate correlations between all variables are presented in Table 2.1.

Age Conservative Belief in God Ingroup Prayer Church Deprivation Children Children Home

Children

Deprivation

Church

Prayer

Ingroup

Belief in God

Conservative

Age

Table 2.1  Bivariate correlations between all continuous variables that were modeled to test sexual signaling theory predictions.

0.07* -0.11*** 0.22*** -0.05 0.14*** 0.25*** 0.02 0.09** 0.20*** 0.15*** 0.00 0.17*** 0.27*** 0.31*** 0.26*** -0.04 -0.07* 0.06 0.03 0.08* 0.03 0.36*** 0.10** 0.09** 0.01 0.18*** 0.12*** 0.10*** -0.48*** 0.04 0.12*** 0.06* 0.07* 0.08* 0.00 0.22***

These correlations are presented for descriptive purposes. The bivariate associations do not adjust for demographic effects, for denominational correlations, or for zero-inflation in rates of prayer and church attendance. We used zero-altered mixed effects regression models deployed in a Bayesian setting to model the probability of zero-outcomes, while at the same time assessing the covariates of non-zero-outcomes. Findings 1a and 1b (signal evaluation):



Table 2.2  Regression model predicting belief in God (left set of panels) and religious ingroup commitment (right set of panels).   b Intercept Prayer (standardized) Church (standardized) Men Partner Age (centered) NZ European Conservative (standardized) Deprivation (standardized) Urban

5.616 0.156 0.269 -0.207 -0.012 -0.010 -0.098 0.203 0.110 -0.052

-95% CI

+95% CI

5.217 0.080 0.193 -0.364 -0.173 -0.015 -0.228 0.126 0.038 -0.208

6.014 0.227 0.341 -0.055 0.153 -0.006 0.056 0.273 0.185 0.100

Religious Group Commitment pMCMC .000 .000 .000 .010 .882 .000 .180 .000 .002 .504

  b 4.049 0.099 0.341 0.168 -0.279 -0.008 -0.190 0.176 0.005 0.052

-95% CI

+95% CI

3.805 0.036 0.273 0.027 -0.422 -0.013 -0.311 0.111 -0.070 -0.088

4.297 0.164 0.405 0.302 -0.134 -0.004 -0.063 0.243 0.059 0.186

pMCMC .000 .004 .000 .016 .000 .000 .004 .000 .889 .449

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Belief in God

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prayer is positively associated with belief in God; church attendance is associated with both religious ingroup entitlement values and belief in God. Models 1a and 1b: Our first statistical model aimed to assess the relationship between inner beliefs and values and outward religious behaviors (prayer and church attendance). Results are presented in Table 2.2. As predicted, we found that prayer was associated with belief in God (β = 0.156, 95 percent HPD interval from 0.08 to 0.23, pMCMC