Sensitivity of N170 and late positive components to social categorization and emotional valence

Previous experiments have shown that categorization of people into two distinct fictive groups has an impact on cognitive processes. The main objective of the present study was to examine whether this mere categorization improves information processing speed and alters early and late onset ERPs during a social judgment task. In a group membership situation, in-group evaluation enhanced information processing speed and occipito-temporal N170 amplitudes, associated with orthographic processing, compared to out-group evaluation, more so for positive than negative attributes. Moreover, negative adjectives elicited larger N170 amplitudes and faster information processing speed than positive adjectives. In contrast, positive adjectives in a non-membership context enhanced a late positive component in prefrontal regions. These results reflect the existence of a motivational top-down influence due to social categorization in early perceptual stages of word processing. These findings are also in accord with the existence of two distinct systems of evaluation, the first implicating an automatic processing represented in occipito-temporal neocortex and the other a more controlled processing represented in PFC.