Every time we see something as a kind of thing, every time that we decide that an object is a cup rather than a glass, when we recognize a picture of a familiar face as a picture of ourselves, or even when we understand speech, we are employing categories. Most categorization decisions are automatic and unconscious, and therefore have the illusion of simplicity. The complexity of these decisions, however, becomes apparent when we attempt to build machines to do what humans perform so effortlessly. What are the systems in place that allow us this extraordinary ability to segment the world? Are they universal? How does conceptual knowledge differ across cultural groups? How do concepts affect our perception? How do the categories of experts differ from the categories of novices? Do children have the same kind of conceptual knowledge as adults? How are categories represented in the brain? In this course, we explore various empirical findings from cognitive psychology, cognitive neuroscience, and anthropology that address these questions.