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Lower order units combined into higher order functional units (e.g., letters into words) are called chunks. The hypothesis tested here suggests that chunks are formed when memories of goal events signal other goal events, a signal capacity that can be reduced when memories are seriously overshadowed by other more valid cues called grouping cues. In support of this hypothesis, it was found, in each of three experiments employing rats in runways, that the capacity of the memory ofnonreward to signal reward depended on its validity relative to that of two other situational cues, runway brightness cues and a change in brightness cues, from one trial to the next. Specifically,the capacity of the memory of nonreward to signal reward was much more seriously reduced when it was in competition with more valid situational cues (.33 vs.

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In memory-discrimination learning, reward-produced memories are differentially rewarded such that they are the only stimuli available to support discriminative responding. Memory-discrimination learning was used in this study as follows: Reward-produced memories that were assumed to regulate instrumental performance in previously reported extinction and discrimination learning investigations were isolated and explicitly differentially reinforced (prior to a shift to extinction) in each of 4 runway investigations with rats. Results obtained here in the explicit discrimination learning stage and in the subsequent extinction stage were consistent with the prediction of the memory view and with prior discrimination learning and extinction findings. The memory interpretation was applied to memory-discrimination learning, to extinction, and to 2 other types of discrimination learning. It appears that a theory must use reward-produced memories to explain all 4 types of discrimination learning.

A common assumption is that expectancies of reward events in instrumental tasks are established on the basis of Pavlovian conditioning. According to the tandem hypothesis, tested in the four runway investigations reported here employing rats, memories of reward events may serve as the conditioned stimuli eliciting expectancies. In Experiments 1-3, rats were trained under a schedule of partial reward (P), which did not produce increased resistance to extinction, and subsequently shifted to consistent reward (C). According to the tandem hypothesis, the shift to the C schedule should result in increased resistance to extinction if, as hypothesized, under the P schedule the memory of reward, SR, came to elicit the expectancy of nonreward, EN' This hypothesis was confirmed under a variety of conditions. It was shown that increased resistance to extinction could not be attributed to the P schedule alone, to the rats receiving two schedules, P and C, to stimuli other than SR eliciting EN, or to the rats forgetting reward-produced memories when expecting nonreward (Experiment 4). It was shown that the tandem hypothesis could explain the divergent findings obtained in prior studies employing a shift from P to C as well as in the present study.