Reinforcement learning and the acquisition of perceptual expertise in ERPs

Abstract

In a category learning task, people are initially unaware when they have committed an error and therefore, require corrective feedback to modify their category decisions. Once the categories are learned, however, external feedback is no longer necessary. Electrophysiologically, the two phases of category learning are indicated by different event-related brain potentials (ERPs): the feedback ERN that is elicited following the presentation of negative feedback and the response ERN that is generated following an incorrect response. In a study of perceptual categorization, participants were asked to discriminate between very similar families of novel geometric shapes (blobs). Participants who learned the perceptual categories (i.e., expert learners) demonstrated a shift from a feedback ERN to the response ERN. The expert learners also showed an enhanced N250 response to the blob families — a component that is thought to index subordinate level representations. For the experts, the buildup of the N250 component was correlated with the shift in the ERN. In contrast, participants who were unable to learn the object families (i.e., novice learners ) failed to show a shift in their feedback-to-response ERN nor did they show an increased N250. Collectively, these results suggest that accompanying the acquisition of the subordinate categories, there is a change from an external source of error monitoring to an internal source.