Neural mechanisms underlying the higher levels of subjective well-being in extraverts: pleasant bias and unpleasant resistance.

The present study investigated the neural mechanisms that underlie the higher levels of subjective well-being in extraverts. The impact of extraversion on the human sensitivity to pleasant and unpleasant pictures of diverse emotional intensities was examined. We recorded event-related potentials (ERPs) for highly positive (HP), moderately positive (MP), and neutral stimuli in the pleasant session, and for highly negative (HN), moderately negative (MN), and neutral stimuli in the unpleasant session, while subjects (16 extraverts and 16 ambiverts) performed a standard/deviant categorization task, irrespective of the emotionality of the deviant stimuli. The results showed significant emotion effects for HP and MP stimuli at the P2 and P3 components in extraverts, but not in ambiverts. Despite a pronounced emotion effect for HN stimuli across the P2, N2, and P3 components in both samples, ambiverts displayed a significant emotion effect for MN stimuli at the N2 and P3 components that was absent in extraverts. The posterior cingulate cortices, which connect multiple neural regions that are important in interactions of emotion and extraversion, may mediate the extravert-specific emotion effect for pleasant stimuli. Thus, extraverts are less susceptible to unpleasant stimuli of mild intensity than are ambiverts, while extraverts have an additional enhanced sensitivity to pleasant stimuli, regardless of emotion intensity. Consequently, the decreased threshold for pleasant emotion and the increased threshold for unpleasant emotion might be essential neural mechanisms that underlie the higher levels of subjective well-being in extraverts.