Abstract
Learned Categorical Perception (CP) occurs when the members of different categories come to look more dissimilar (“between-category separation”) and/or members of the same category come to look more similar (“within-category compression”) after a new category has been learned. To measure learned CP and its physiological correlates we compared dissimilarity judgments and Event Related Potentials (ERPs) before and after learning to sort multi-featured visual textures into two categories by trial and error with corrective feedback. With the same number of training trials and feedback, about half the subjects succeeded in learning the categories (“Learners”: criterion 80% accuracy) and the rest did not (“Non-Learners”). At both lower and higher levels of difficulty, successful Learners showed significant between-category separation—and, to a lesser extent, within-category compression—in pairwise dissimilarity judgments after learning, compared to before; their late parietal ERP positivity (LPC, usually interpreted as decisional) also increased and their occipital N1 amplitude (usually interpreted as perceptual) decreased. LPC amplitude increased with response accuracy and N1 amplitude decreased with between-category separation for the Learners. Non-Learners showed no significant changes in dissimilarity judgments, LPC or N1, within or between categories. This is behavioral and physiological evidence that category learning can alter perception. We sketch a neural net model predictive of this effect.
Highlights
The linguists Sapir (1929) and Whorf (1940; 1956) suggested that the language we speak shapes the way we see the world
The researchers found changes in the activity of both the anterior fusiform gyrus and the extrastriate occipital cortex when the cars differed on the category-relevant dimension. This suggests that learning a category enhances the Neural correlates of learned categorical perception detectability of distinguishing features in the temporal association cortex that is related to high level visual processing, and in earlier stages of perception that take place in the extrastriate visual cortex [29,43]
We analyzed changes induced by category learning behaviorally and electrophysiologically (Event Related Potentials; ERPs) to test whether Categorical Perception (CP) effects are induced by category learning, whether they are perceptual, and what role they play in the mechanisms underlying category learning
Summary
The linguists Sapir (1929) and Whorf (1940; 1956) suggested that the language we speak shapes the way we see the world. According to this “linguistic relativity” hypothesis, it is learning to put things into different categories by giving them different names that makes them look more distinct to us, rather than vice versa [1]: for example, the rainbow looks to English-speakers as if it were composed of qualitatively distinct color bands because of the way English subdivides and names the visible wavelengths of light; the different shades of green all look like greens rather than blues because in English we learn to call them “green” rather than blue. In languages that use the same word for green and blue
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