Marking,Memory and Superstition in the Pigeon

Abstract

Learning is generally poor if reinforcement is delayed, but it improves substantially if a brief stimulus is presented immediately after the response to be learned. The marking hypothesis suggests that the unexpected stimulus triggers a backward memory search, which effectively marks the preceding response in memory, making it more likely that it will be recalled when food is presented. In the present study, pigeons were occasionally reinforced after a 10-sec delay for pecking a split key. Reinforcement was presented regardless of which side was pecked, but for one group a marker followed a peck to the left half of the key during the delay preceding food, and for the other group a peck to the right. On non food trials these contingencies were reversed. Subjects developed a significant preference for the side marked on food trials, despite the absence of any contingency between responding to this side and food. In addition to providing further support for the marking hypothesis, these results favour theories of reinforcement emphasizing contiguity rather than contingency. Contiguity, however, needs to be interpreted within a memory framework. What is crucial is the contiguity of events within working memory, rather than in the real world.