Latent inhibition and learned irrelevance of occasion setting

Rats received serial feature-positive discrimination training (A --> X+/X-) within a conditioned lick suppression preparation (with + representing rei nforcement and - representing nonreinforcement). In Experiment 1, the featu re (A) was found to modulate responding to a transfer target CS that itself had been occasion set with a second occasion setter, but not to a CS that had been partially reinforced, thereby demonstrating occasion setting with our preparation. Experiments 2-4 examined the effects on the acquisition of occasion setting of various types of pretraining exposure to A. Nonreinfor ced preexposure to A alone did not in any way retard acquisition and/or exp ression of occasion setting (Experiment 2), but feature-negative discrimina tion training did (Experiment 3). A feature-irrelevant pseudo-discriminatio n pretraining procedure produced profound retardation (Experiment 4). The r esults of Experiments 2 and 3 indicate that a latent inhibition-like effect for feature-positive occasion setting exists that in some ways is analogou s to latent inhibition effects in Pavlovian conditioning. The results of Ex periment 4 indicate that an analogue of Pavlovian learned irrelevance can b e evidenced for feature-positive occasion setting. The growing parallels be tween occasion setting and simple Pavlovian conditioning lend support to ac counts of occasion setting that view it as arising from an interaction of P avlovian associations rather than from some distinctly different "higher or der" process. (C) 1999 Academic Press.