Category learning can alter perception and its neural correlates

TL;DR

This study demonstrates that learning categories can change perception and neural responses, with successful learners showing increased between-category separation in judgments and specific ERP changes, unlike non-learners.

Contribution

It provides behavioral and neural evidence that category learning can modify perceptual processes and identifies associated ERP correlates.

Findings

Successful learners showed increased between-category separation after learning.

ERP analysis revealed increased late parietal positivity (LPC) in learners.

Occipital N1 negativity decreased in learners after learning.

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 trials and feedback, about half the participants 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 in pairwise dissimilarity judgments after learning compared to before; their late parietal ERP positivity (LPC, usually interpreted as decisional) also increased and their occipital negativity (N1) (usually interpreted as perceptual) decreased. LPC 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 for this effect.