The present experiment is an attempt to investigate stimulus generalization gradients resulting from the reinforcement of two stimuli on the same continuum. The general problem derives from Hull's treatment of the summation of generalization gradients (4, 5; Postulates 4 and S, Major Corollary I). These postulates state that overlapping generalization gradients will summate exponentially to yield a resultant gradient of greater response strength. Wolfle (7) has made a similar assumption to the effect that gradients generated from training at several points on the stimulus continuum will reinforce each other.Until a recent study by Bilodeau, Brown, and Meryman (1), no explicit investigation of this problem had been undertaken. Their experiment used an instructed voluntary response rather than a conditioned response, presumably because of the technical difficulties inherent in the latter. The conditioning technique employed by the present authors (2), however, provides a more direct approach to the question.
METHODSubjects.-The Ss were 22 experimentally nai've pigeons maintained by restricted feeding
Fear is usually defined as an anticipatory conditioned response to cues preceding pain (8,10). It is assumed that fear functions as a cue (6) and as a drive (7). A number of studies (1, 2,3,6,7,9) have indicated that fear can motivate behavior and when reduced in strength can reinforce the immediately preceding responses.In a recent survey of acquired drives, Miller (8) has indicated that if fear has the characteristics of a response, then its intensity, the probability of its occurrence, and its resistance to extinction should vary with those factors which affect the acquisition and extinction of other responses. On this basis, it is reasonable to expect fear to increase as a monotonic function of the number of conditioning trials and to weaken progressively with successive extinction trials.The available data bearing on this expectation are fragmentary and in-1 This report is a portion of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Psychology, State University of Iowa. The writer is indebted to Dr. Judson S. Brown for his guidance during the experimental investigation and the preparation of the manuscript.
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