Abstract:

It is widely reported that monetary reward improves performance of cognitive tasks, such as spatial orienting, visual search, and conflict control by increasing task concentration and engagement. The current study used event-related potentials (ERPs) technique to investigate the impact of monetary reward on the discrimination of emotional facial expressions. Participants were asked to discriminate a happy, neutral, or angry face presented at the center of the computer screen, which was preceded by a monetary incentive or a non-incentive cue, and was followed by a feedback stimulus regarding the fastness and correctness of the response. Participants were informed that they would gain additional monetary reward if their reaction times (RTs) on incentive trials meet certain criteria. Behavioral results showed that RTs to emotional faces were generally faster than to neutral faces, and RTs in incentive trials were faster than that in non-incentive trials. Cue-elicited ERPs were modulated by monetary incentive, such that incentive cue elicited larger P1 (130~200 ms), P2 (200~300 ms), and P300 (300~600 ms) amplitude than the non-incentive cue. Target-elicited occipito-temporal P1, N170 and frontal-central N300 amplitudes were modulated by reward anticipation, such that target elicited more positively-going ERPs in incentive condition than that in non-incentive condition. Early P1, N170 and VPP amplitudes were not affected by emotional facial expressions. The neural processes involved in processing emotional faces (happy, angry) and neutral faces diverged 300 ms after stimulus onset. Results showed more positive N300 in emotional conditions than in neutral conditions. Additionally, the amplitude of N300 was influenced by both reward anticipation and emotional valence. While the positive emotion processing effect was not modulated by reward anticipation, the negative emotion processing effect and negative bias effect for the N300 component were larger in incentive condition than in non-incentive condition. These results suggested an impact of reward anticipation on the processing of upcoming emotional facial expressions. Motivational factors may modulate the distribution of attentional resources, which then bias the processing of negative emotion.

Key words: monetary incentive, emotional facial expression, negative bias, attentional resources, event-related potential