Anterior N2 predicts subsequent viewing time and interest rating for novel drawings

Event-related brain potentials (ERPs) in response to novel pictures and subsequent visual exploration were examined. Eighteen undergraduates viewed 120 novel drawings as long as they wished. ERPs were calculated separately for drawings that were viewed longer or shorter than the median viewing time of each participant. The drawings viewed longer elicited a larger anterior negativity (N2) peaking at 245 ms than the shorter viewed drawings. This effect disappeared and the overall amplitude of the N2 decreased when the same set of drawings was presented again in a subsequent interest-rating session. Drawings rated as more interesting elicited a larger N2 than did drawings rated as less interesting. This study demonstrates a type of anterior N2 that is sensitive to stimulus unfamiliarity or difficulty in encoding, which reflects a conflict between stimulus input and existing knowledge and prompts further recognition processes and visual exploration.