The decade of the 1990s witnessed acceleration in the convergence of theoretical and experimental studies of discrimination and generalization from the domains of classical conditioning and instrumental (operant) learning. Classical conditioning refers to the establishment of behavioral adaptations (conditioned responses; CRs) by the methods of Pavlov. Instrumental learning is a general term for goal-seeking behavior, and operant conditioning refers to reinforcement learning by the methods of Skinner. The term discrimination refers to the capacity of organisms to learn different modes of behavior depending on signals or cues from the environment about the imminence or accessibility of reinforcement. Generalization refers to stimulus generalization, the capacity for signals or cues that are different from those used for establishing learned behavior to evoke this behavior. Stimulus generalization in classical conditioning refers to the capacity of a stimulus other than the conditioned stimulus to evoke a CR. In...