Preface. Part 1: Psychophysical Origins of Difference and Similarity 1. The Elements 2. Challenges and Extensions 3. The Origin of the Psychometric Function 4. The Law of Comparative Judgment 5. Equality and Affective Value 6. The Psychological Ideal 7. Discrimination and Response Bias 8. Discrimination and Response Strategy. Summary. Part 2: Wave Theory 9. Wave Discrimination Theory 10. Response Probabilities and Response Times 11. Response Bias 12. A New Theory of Variability 13. A Theory of Sensation 14. Discriminability and Responsiveness 15. A Theory of Feeling 16. Bias, Responsiveness, and Strategy 17. Wave Similarity Theory. Apendices A, B, C. References. Author Index. Subject Index.