The role of blocking and compensatory conditioning in the treatment preexposure effect.

Rats were given injections of an aversion-inducing drug in one environment, and then conditioned to avoid a novel-tasting saccharin solution. The treatment preexposure effect (i.e., reduced conditioning) was obtained when preexposure and aversion training took place in the same environment, but not in different environments. Additional experiments, which showed that consumption of a novel saccharin solution was selectively enhanced, rather than reduced, following exposure to aversion-inducing drugs, gave evidence that interference in the formation of conditioned taste aversions was not the result of associative blocking. Results of the final experiment suggested that enhanced drinking may have occurred because stimuli that characterized the environment in which preexposures were administered suppressed the action of the pituitary-adrenal system.