Cue Competition and Inhibitory Conditioning
Hull (1929) thought that “all elements of a stimulus complex playing upon the sensorium of an organism at or near the time that a response is evoked, tend themselves independently and indiscriminately [italics added] to acquire the capacity to evoke substantially the same response” (p. 498). He was wrong. The modern era in the study of conditioning began with the discovery that conditioning to one CS does not proceed independently of the other CSs present. The more or less simultaneous discovery of the effects of background conditioning (Rescorla, 1968), of blocking and overshadowing (Kamin, 1969a, 1969b), and of relative validity (Wagner, Logan, Haberlandt, & Price, 1968) made the point that what an animal learns about one CS strongly affects what it learns about other CSs. Or, possibly, what it has learned about other CSs strongly affects the behavioral expression of what it has learned about any one CS (cf. Miller’s Comparator Hypothesis; Cole, Barnet, & Miller, 1995a; Miller, Barnet, & Grahame, 1992). The discovery of cue competition changed the character of associative models; it led to the model by Rescorla and Wagner (1972) and to other contemporary associative models that explain how experience with one stimulus affects the observed conditioning to another stimulus (e.g., Mackintosh, 1975; Miller & Matzel, 1989; Pearce, 1994; Pearce & Hall, 1980; Wagner, 1981). All such models attempt to explain how cues interact in conditioning. The general term for this interaction is cue competition. As we will see, an understanding of cue competition leads to an understanding of inhibitory conditioning, the conditioning that occurs when the CS predicts a reduction in the rate of reinforcement.