often thought to be the case. An additional striking example that underscores that point comes from research by Allport, Tipper, and Chmiel ( 1985). They presented subjects with trials consisting of a prime stimulus followed by a probe stimulus. Both stimuli consisted of a red letter and a green letter on top of each other (the prime might be a red A and a green B, for example, and the probe might be a red C and a green D). At the end of a trial, subjects were asked first to name the red letter in the probe stimulus and then to recall the red letter from the prime stimulus. On the trials where the green (to-be-ignored) letter in the prime stimulus was repeated as the red (to-be-named) stimulus in the probe stimulus, there was an inhibitory effect: The subjects were slowed down in their ability to name that letter. On the final trial of the experiment, subjects--rather than being presented a probe stimulus--were asked to recall the green (to-be-ignored) letter from the preceding prime stimulus. The fact that few subjects could do so indicates that a kind of active retrieval inhibition was responsible for the slowed encoding observed by Allport et al. ( 1985).
In all likelihood, the general thesis in this chapter--that inhibitory processes play a critical role in the overall functioning of human memory--will seem uncontestable in the near future, possibly even by the time this chapter appears in print. A new metaphor has emerged to influence the thinking of memory researchers: the brain metaphor. As other chapters in this volume attest, our ideas about memory are being shaped by the accelerating knowledge of the possible functions of certain brain structures in human memory. In addition, the neural/connectionist approach to the simulation of cognitive processes is being pursued with enthusiasm and high expectations. In contrast to the computer metaphor, which tended to lead us away from explanations based on inhibitory processes, the brain metaphor, if anything, will push us towards such explanations.
Preparation of this essay was aided by a grant from the Academic Senate of the University of California. The author thanks James Neely, Larry Jacoby, Elizabeth Bjork, and Tom Minor for useful comments and criticisms, and Henry Roediger for his unsparing efforts to edit this chapter.
Allport D. A., Tipper S. P., & Chmiel N. R. J. ( 1985). "Perceptual integration and postcategorical filtering". In M. I. Posner & O. S. I. Marin (Eds.), Attention and performance, XI (pp. 107- 132). Hillsdale, NJ: Lawrence Erlbaum Associates.