This chapter presents a framework for understanding the most promising contributions of psychological methods and insights for private law. It focuses on two related domains of psychological research: cognitive and social psychology. Cognitive psychology is the study of mental processes, which one might shorthand as “thinking.” Social psychology asks about the role of other people—actual, implied, or imagined—on mental states and human behavior. The chapter is oriented around five core psychological insights: calculation, motivation, emotion, social influence, and moral values. Legal scholarship by turns tries to explain legal decision-making, tries to calibrate incentives, and tries to justify its values and its means. Psychology speaks to these descriptive, prescriptive, and normative models of decision-making. The chapter then argues that psychological analysis of legal decision-making challenges the work that the idea of choice and preference is doing in private law, especially in the wake of the law and economics movement.