Evidence for "unique stimulus" account of configural conditioning.

Abstract

Four experiments are presented which test the proposition that a compound stimulus, AB, may be conceptualized as composed of the individual A and B elements as well as a separate stimulus unique to their combination. Together with an assumption about limitations on the total associative strength of the compound, that conceptualization can account for the learning of various configural conditioning paradigms. Each experiment examines whether the hypothesized unique stimulus has properties like those of a separable element. The results indicate that, like the separate elements, the unique stimulus can acquire associative strength which is either excitatory or inhibitory, which summates with other associative strengths, which influences the effectiveness of reinforcement and nonreinforcement, and which is attenuated when the unique stimulus becomes irrelevant to reinforcement. In many learning situations it is possible to account for the behavior produced by a stimulus compound in terms of some combination of the behaviors produced by the elements of that compound. For instance, simultaneous presentation of stimuli separately trained to produce a response will normally result in evidenced by a response more vigorous than that to either stimulus (e.g., Konorski, 1948; Pavlov, 1927). Similarly, combination of 2 stimuli, one of which has been trained to evoke a response and the other of which has been trained to inhibit that response, results in summation evidenced by a response of intermediate value (e.g., Pavlov, 1927; Rescorla, 1969). However, the results of a number of learning situations do not seem compatible with simple summation notions. For instance, it is possible to train an organism to respond to the separately presented elements of a stimulus compound, but to withhold its response from the compound itself. Similarly, organisms can be trained to re1 This research was supported by National Science Foundation Grants GB-12897 and GB28703X. Thanks are due to Karen Gould and Barbara Steinfeld for aid in data collection and analysis. a