Second-order conditioning with and without unconditioned stimulus presentation.

Abstract

The effects of presenting various episodes after serial presentation of two conditioned stimuli (CS2-CS1 sequences) on second-order conditioning to CS2 were examined in three experiments using rat subjects in an appetitive conditioning situation. In Experiment 1, presentation of food unconditioned stimuli (USs) immediately after CS2-CS1 sequences interfered with second-order conditioning of CS2. In Experiment 2, postsequence presentation of a "surprising" US interfered with second-order conditioning more than did presentation of an "expected" US; similarly, less second-order conditioning of CS2 was observed when postsequence nonpresentation of a US was surprising than when US omission was expected. In Experiment 3, the interfering effect of US presentation on second-order conditioning was smaller when a brief delay was introduced between presentation of the CS2-CS-1 sequence and the US. The results are discussed in terms of an information-processing theory recently proposed by Wagner and his colleagues.

Variations in Unconditioned Stimulus Processing in Unblocking.

“…Second, in Experiment 2, CN-lesioned rats showed more acquisition of within-compound noise-light learning after downshifts than sham-lesioned controls. As outlined earlier, previous data (Holland, 1980(Holland, , 1985a suggest that greater within-compound learning occurs when processing of subsequent USs is minimized. If sucrose omission enhanced processing of food in sham-lesioned but not CN-lesioned rats, then greater noise-light learning would be anticipated in CN-lesioned rats.…”

“…Using a conditioning procedure similar to that used here, Holland (1980Holland (1985a found that presentation of a food US after serial compound cues interfered with within-compound learning. Furthermore, Holland (1980) found that such interference was enhanced when processing of the interfering US was enhanced by procedures that rendered that US more surprising.…”

“…Using a conditioning procedure similar to that used here, Holland (1980Holland (1985a found that presentation of a food US after serial compound cues interfered with within-compound learning. Furthermore, Holland (1980) found that such interference was enhanced when processing of the interfering US was enhanced by procedures that rendered that US more surprising. In the context of Experiment 2, in sham-lesioned rats, enhancement of processing of the food US (by sucrose omission) might especially interfere with the formation of the noise-V1 associations that are responsible for the sucrose cup behavior controlled by the noise.…”

Perceptual learning in flavor aversion: Evidence for learned changes in stimulus effectiveness.

“…If so, then the representation of A could be activated by the Y element in rats tested with BY and CY, and B-A inhibition could still act to reduce the degree of the aversion shown to the BY compound. Whether two AY trials would be sufficient to establish an appropriately strong Y-A association is open to debate, particularly in view if the fact that each was followed by a potent US, a procedure known to detract from the formation of within-compound associations (Holland, 1980). This doubt was enough to encourage us to attempt another, and potentially more decisive, test of the alternative theories.…”

Temporal primacy overrides prior training in serial compound conditioning of the rabbit’s nictitating membrane response

“…Elsewhere, partial blocking of response acquisition to CSA has been reported in taste aversion learning (Revusky, 1971, pp. 197-203), odor aversion learning (Cheatle & Rudy, 1978), and conditioned suppression (Kohler & Ayres, 1982;Pearce, Nicholas, & Dickinson, 1981), but not in conditioned activity (Holland, 1980). Levels of responding to CSB have been largely unreported.…”