Images of tactile intimacy in same-sex dyads elicit larger P2 and LPC amplitudes

There is considerable behavioral evidence suggesting that the tactile intimacy between same-sex dyads might be viewed negatively. However, there is no electrophysiological evidence. In order to address this issue, event-related potentials (ERP) were recorded when both male and female participants were asked to evaluate whether the behaviors in same-sex dyads were appropriate or not. Both participant groups responded faster when they evaluated intimate pictures showing two males. The female participants were more inclined to tolerate female same-sex intimate pictures than the male participants. The deflections of P2 (150–250 ms) and LPC (400–600 ms) were significantly amplified in the intimate condition than in the non-intimate one, indicating that same-sex intimate pictures elicited negative emotions in participants. The female intimate pictures elicited larger LPC (600–900 ms) than the male intimate pictures only in the case of the female participants, indicating that female participants might enjoy in same-sex interactions as the dyads shown in the picture, and greater processing resources were required in evaluating processes. Above all, behavioral and electrophysiological scalp data provided the evidence that the tactile intimacy between same-sex dyads was viewed negatively.