Preschool children who did not group a set of geometric stimuli according to complete similarity on a pretest were taught classification wither in a modeling or in a reinforcement condition. Modeling was found to be an effective means of teaching classification behavior. (ST)

To the authors' knowledge, this is the first demonstration that from observation alone, unaided by other means of conveying information, a concept can be retained and generalized to novel stimuli after a substantial elapse of time. (Authors/MB)