This is an excerpt from a report on the Perceptual Learning and Perceptual Recognition Workshop at the University of York in March of 2012, written by Kevin Connolly, Dylan Bianchi, Craig French, Lana Kuhle, and Andy MacGregor, and available at http://networksensoryresearch.utoronto.ca/Events_%26_Discussion.html 3. How Does Perceptual Learning Alter Perceptual Phenomenology? Some philosophers argue that perceptual learning enriches perceptual phenomenology. Charles Siewert, for instance, writes that after we learn to recognize some general type, such as a sunflower, certain features "'stand out for us as significant' and 'go together.'" Such cases, he argues, show the "wealth" or "richness" of visual experience (Siewert, 1998, pp. 255, 259). In the workshop, however, an alternative account arose for how perceptual learning alters perceptual phenomenology. In his commentary on Ian McLaren, Kevin Connolly argued that one implication of McLaren's account is that perceptual learning in fact impoverishes one's perceptual phenomenology. Ian McLaren has explored the influence of "latent inhibition" on perceptual learning: subjects pre-exposed to a stimulus have more difficulty being conditioned on that stimulus than on a novel stimulus. For example, R.E. Lubow and A.U. Moore (1959) found that if first shown a light ten times, sheep were slower to associate a shock with the light than with a novel stimulus-a turning rotor. McLaren argues that this is because pre-exposed stimuli tend to be less salient than novel stimuli by latent inhibition. Here, perceptual learning decreases the salience of features that a stimulus shares with other stimuli. Thus, the unique features of the stimulus become more salient by comparison. For example, according to McLaren's account of face recognition, exposure to a variety of faces renders common features less salient and unique features relatively more salient. 2 In his commentary on McLaren's talk, Connolly pointed out that philosophers often focus on increased salience in perceptual learning. Siewert, for example, writes: "Notice how different your neighborhood looks to you now that you have lived there for a while, than it did on the day you first arrived" (1998, p. 257). Is this a difference in increased or reduced salience? Arguably (and McLaren later agreed with this), the familiar features of your neighborhood become less salient over time and this accounts for the difference in phenomenology. Further, if McLaren is right, features that are salient at one time might not be salient at another time. Susanna Siegel argues that for someone who has recently learned to distinguish pine trees from non-pine trees, pine trees look visually salient (2010, p. 100), and become a part of visual phenomenology. On McLaren's account, Connolly argued, unique features can become familiar over time. But if pine tree salience doesn't hold constant, why think that pine trees remain part of your visual phenomenology? Finally, on McLaren's account, the features common to pine trees and non-pine trees decrease in salience, thereby creating a differential between those common features and the features unique to pine trees. So, why think that perceptual learning is enriching your perceptual phenomenology at all? It is relevant, though, what is salient. Arguably, McLaren's focus is on feature salience, while Siegel's is on object or kind salience. Kind salience could be mediated by unique features. References: Lubow, R.E., and Moore, A.U. (1959). "Latent inhibition: The effect of non‐reinforced preexposure to the conditional stimulus." Journal of Comparative and Physiological Psychology, 52, 415-419. Siegel, Susanna (2010). The Contents of Visual Experience. Oxford: Oxford University Press. 3 Siewert, Charles (1998). The Significance of Consciousness. Princeton: Princeton University Press.