Temporal determinants of occasion setting in feature-positive discriminations

Abstract

Three experiments examined the acquisition and transfer of Pavlovian feature-positive discriminations (XA+, A-) in rat subjects. To identify the nature of the associations formed in those discriminations, the form of the conditioned responses (CRs) was examined. If the feature, X, and common element, A, cues started and ended together on XA compoud trials, associations between X and the food unconditioned stimulus (US) were acquired. If the onsets and/or terminations of X preceded those of A, X acquired the ability to set the occasion for responding to A, that is, A evoked CRs only on XA compound trials. The acquisition of occasion setting was favored when (1) the onset of X preceded that of A, (2) the interval between X and A and/or the US was relatively long, and (3) the termination of X occurred prior to the onset of A. The occasion-setting power of X was fairly specific to A:X did not modulate responding evoked by another cue that had been first trained and then extinguished or by a cue that had been paired with the US only a few times. However, X did enhance responding to a cue that had been a common element in another, identical feature-positive discrimination. That transfer was somewhat greater if the X and A terminated together than if X terminated prior to the onset of A. Implications for theories of stimulus control in Pavlovian conditioning are discussed. © 1986 Psychonomic Society, Inc.