Perceptual Learning: Effects and Mechanisms

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Experts in a variety of fields (e.g., professional wine-tasters, experienced radiographers) show the ability to make fine discriminations that nonexperts find impossible. Skills of this sort are acquired as a result of experience, partly by way of explicit training (as when an expert instructs his apprentice), but also simply as a consequence of appropriate exposure to the items to be discriminated / the opportunity to compare two wines, or two images appears to be critical here. This perceptual learning effect can be demonstrated in the laboratory -- naive individuals, presented with complex visual displays that are initially indistinguishable, become able to tell them apart after repeated exposure when this is arranged in a way that allows comparison between different displays. Our proposal makes use of this laboratory procedure to answer two basic questions about perceptual learning. First, experience with the stimulus allows it to be perceived differently. But what is the nature of the change in the perceived stimulus? We plan to do experiments that will test the suggestion that, for the experienced observer, the distinctive features of the stimulus come to stand out and attract attention, whereas other aspects of the stimulus display lose effectiveness. Second, we want to know about the mechanisms that are responsible for this form of learning. What learning processes are responsible for changing the perceptual effectiveness of a stimulus? Previous work has shown that perceptual learning effects obtained in studies of animal learning can be generated by the operation of very simple learning processes (specifically, those known as habituation and association formation). Our experiments will test the application of these concepts to the human case.