Stimuli associated with drug injections as events that control behavior.

In this paper, some of the ways were briefly reviewed in which environmental stimuli that have been associated with injections of morphine or narcotic antagonists can come to modify and control behavior. Many of the effects described have also been demonstrated with drugs from other pharmacological classes. Environmental stimuli that occur in association with human drug-seeking and drug-taking behavior play an important role in the development, control, and perpetuation of this behavior. A variety of approaches to the experimental analysis of the control of behavior by such stimuli have been illustrated. Studies with these approaches promise to expand our understanding of the dynamic processes involved in drug use by human addicts.