The fate of redundant cues during blocking and a simple discrimination.

In each of three experiments animals received blocking, A+ AX+, in which food was always presented after one stimulus, A, that was occasionally accompanied by another stimulus, X. They also received a simple discrimination, AX+ BX-, in which the presence and absence of food was signaled by two compounds that contained one unique cue, A or B, and one common cue, X. In each of these designs, X can be said to be redundant relative to A as a signal for food. Test trials at the end of training revealed that responding during X was stronger after blocking than after the simple discrimination. These results contradict predictions from theories of learning that assume changes in associative strength of a stimulus are determined by a global error term based on the outcome predicted by all the stimuli that are present for a conditioning trial. The results are interpreted, instead, by assuming either that animals store a memory of every trial to which they have been exposed, or that learning is governed by an error term based on the significance of individual stimuli. (c) 2012 APA, all rights reserved.