Overshadowing of Occasion Setting

Much research has been conducted investigating the rules that govern Pavlovian conditioning. In contrast, much less has been determined to date concerning the rules that govern occasion setting. Occasion setting might be better understood if researchers initially sought analogies between occasion setting phenomena and phenomena known to occur in Pavlovian conditioning. Toward this end, we examined overshadowing of occasion setting. Experiment 1 demonstrated feature-positive occasion setting with rats in a conditioned suppression preparation. Experiment 2 found overshadowing of occasion setting. Experiment 3 demonstrated that overshadowing of occasion setting can be attenuated by posttraining degradation of the overshadowing occasion setter's modulatory potential, which suggests that overshadowing of occasion setting, like overshadowing of Pavlovian conditioning, is at least in part a failure to express acquired information rather than a failure of acquisition. These studies add to the growing evidence of strong similarities between Pavlovian excitatory conditioning and occasion setting, which favor models that account for occasion setting through the same principles as excitatory conditioning rather than a separate set of modulatory mechanisms.