Learning to categorize objects stands among the most fundamental cognitive processes. Categorizing brings order and organization to our mental lives, and is a building block of more complex cognitive processes such as reasoning, problem solving, and thinking. Central issues in the study of categorization include how categories are represented in memory, and what decision processes are involved when people make categorization judgments. Furthermore, how are these category representations learned? Researchers often pursue these questions by developing formal models of categorization, and testing these models in experiments in which subjects learn new, artificial categories in laboratory settings.