| Abstract No.: | C-G3188 |
| Country: | Canada |
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| Title: | EVENT-RELATED POTENTIALS REFLECT CATEGORICAL PERCEPTION INDUCED BY LEARNING. |
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| Authors/Affiliations: | 1 Bernard St-Louis*; 1 André Achim; 1 Stevan Harnad;
1 Université du Québec à Montréal, QC, Canada.
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| Content: | Objectives: Categorical Perception (CP) occurs when two members of the same category are harder to discriminate than members of two different categories even when the physical differences between them are equal. This compression/separation effect has also been found to result from learning, by comparing within and between-category discriminability before and after learning. Our objective was to test whether learned CP is reflected in the Even-Related Potential (ERP), and, if so, whether its effect is sensory or decisional.
Methods: Participants were tested for CP before and after a series of categorization training trials with corrective feedback. CP was tested using a modified ABX discriminability method. ERPs were measured during the ABX trials. In an unlearned obvious-category category condition the category differences were made so big that categorization performance was error-free without training. In the experimental condition ABX was tested before and after the categorization had been mastered.
Results: In the learning condition, ABX performance before training was flat (no difference between ABA and ABB when A and B were in different categories), and no corresponding ERP differences either. In the unlearned obvious-category condition, there were significant differences in occipital-parietal ERPs between A and B in the first position in ABX and significant differences also between AAX and ABX at the second position. The ABX pattern after successful learning was the same as that for the unlearned obvious-category condition.
Conclusions: It was demonstrated that in CP learning, the changes in performance are accompanied by changes in the ERP correlated with changes in the perceptual disriminabillity of the stimuli. These is a physiological indicator of the Whorf-Sapir effect, that the perceptual world changes in appearance depending on how we sort and name things. |
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