Environmental determinants of the reinforcing effects of nicotine in humans.

Experimental studies indicate instructions (told received nicotine > told received placebo) and drug history (exsmokers > never-smokers) increase the degree to which the stimulus effects of nicotine will serve as a reinforcer in humans. Cross-study comparisons and correlational data suggest schedule (concurrent > single access to nicotine and placebo), duration of exposure (longer > shorter exposure), and setting (therapeutic > experimental settings) also increase the reinforcing effect of nicotine. Empirical study of when and how environmental factors control the reinforcing effects of nicotine is crucial to specifying multicausal models of tobacco dependence.