The following questions are addressed: (1) When a panel of appellate judges considers a specific case, is each judge's vote based on precedents and logic, or is it a manifestation of that judge's predispositions and values? (2) Is the panel's eventual ruling a results of reasonable deliberations or of persuasion and conformity pressures? Chapters One through Five examine competing explanations of judicial decision-making and reflect the application of psychological knowledge to the preceding questions. Central to this book's analysis is the proposition that a court decision reflects the preferences of its individual members yet is also a group decision that reflects the interactions among its members. The second half of the book explores psychology's relevance to judicial decision-making in a different and more precise way. The issue of same-sex marriages is selected as an introductory example partly because it is an issue about which psychology has something to say. Over the last 50 years, organized psychology has attempted to influence the outcome of some decisions by the U.S. Supreme Court and other appellate courts, mostly through the use of the amicus curiae briefs. The second half of the book provides detailed examples of successful and unsuccessful amicus briefs and draws conclusions about how psychology and the other social sciences can best have useful influence on judicial decision-making. 405 references and name and subject indexes