Concepts, the mental categories used to organize events and objects, are often arranged in hierarchical order from general to more specific—for example, organism, animal, vertebrate, quadruped, dog, collie. Such categories help people to understand new information and to plan—for example, by dividing available time into periods for study, class attendance, recreation, and so forth. People tend to use a prototype, a model of a concept, to typify members of a particular category. The prototype any particular individual uses depends on that individual's experience. Your prototype of “dog,” for example, might be a longhaired, medium‐size, long‐muzzled, black and white, tail‐wagging animal, and you would tend to classify dogs that you encounter as in various ways being the same as or different from your prototypical dog. Theories of concept formation The term mediation theory refers to the process used in forming connections between things previously not connected. The hypothesis‐testing theory considers concept formation to be an active process in which people acquire information by generating hypotheses about stimuli, testing the hypotheses, and accepting them or discarding them and formulating others.