Why does our ability to reason sometimes fail us? Why do we occasionally make choices that are bad for us? We address these questions by surveying experimental approaches to understanding reasoning and decision-making processes in human behavior, and by solving and analyzing problems that psychologists have used to investigate these processes. Class discussion focuses on cognitive theories of rational and irrational thinking as well as behavioral theories of suboptimal choices. Topics include impulsiveness and self-control, the subjective values of short-term versus long-term rewards, addictions and bad habits, probability judgments, gambling, and moral reasoning. Students may conduct original research in one of these areas. Format: lecture/discussion. Requirements: short papers, a written report of research project, and class participation. Prerequisites: Psychology 221 or permission of instructor. Enrollment limit: 19 (expected: 15). Empirical Project