AbstractData are summarized which indicate that drug discriminative stimuli (DDS) and exteroceptive, sensory stimuli interact in a systematic manner. Thus recent work revealed that phenomena such as overshadowing, blocking, and conditional discrimination are operable in drug discrimination learning (DDL) experiments involving exteroceptive cues and DDS. Additionally, in a reversal learning experiment, a contextual change differentially affected rate of reversal learning and subsequent generalization test data.