stimulus–stimulus learning model: any learning theory that is cognitive in nature and emphasizes the formation of associations between stimuli, in contrast to theories based on stimulus–response connections (see S–R psychology). Examples include purposive behaviorism and Gestalt learning theory. In classical conditioning, the S–S learning model postulates associations between conditioned and unconditioned stimuli; in instrumental conditioning, the association is between the discriminative stimulus and the reinforcing stimulus or outcome (i.e., the S–O association).