Psychological similarity—the subjective distance between objects in the world or memory—is a highly influential concept in many areas of cognitive psychology, such as learning, memory, categorization, judgment, and preferential choice. The contributions within this symposium will evaluate the fundamental role that similarity plays in human judgment and decision making. We bring together experts from distinct subdisciplines of psychology, who examine the influence of similarity on categorization, consumer choice, risky choice, social norms, and in memory-based choices. Specifically, the contributions elaborate on three key questions repeatedly pursued within cognitive psychology: 1) how does similarity activate previous experiences and renders them available within a given choice context? 2) how does similarity interact with feature or knowledge abstraction processes? 3) how is similarity represented psychologically? To reach this goal, the contributions within this symposium focus on reinstating similarity-based processes within formal cognitive models and test their predictions experimentally.