Previous studies have shown that sharing an experience, without communicating, affects people’s subjective perception of the experience, often by intensifying it. However, the effect of shared experience on the underlying neural processing of information is not well understood. In this study, we aimed to investigate the neural mechanisms underlying shared attention by implementing a dual- EEG study where participants were required to attend to and judge the intensity of neutral, angry and happy faces, simultaneously or independently. In order to study whether the presence of another individual modulates an individual's perception and processing of facial expressions, we implemented three experimental conditions: 1) participants performed the task alone, in the absence of a social context (unshared condition), 2) participants performed the task simultaneously next to each other in pairs, without receiving feedback about the other participant's responses (shared no feedback) and 3) participants performed the task simultaneously while receiving the feedback (shared with feedback). We focused on two face-sensitive ERP components: the N170 and the Early Posterior Negativity (EPN). We found that the amplitude of the N170 was greater in the shared with feedback condition compared to the other conditions, reflecting a top-down effect of shared attention on the structural encoding of faces, irrespective of valence. In addition, the EPN was significantly greater in both shared context conditions compared to the unshared condition, reflecting an enhanced attention allocation in the processing of emotional content of faces, modulated by the social context. Behaviourally, we found a modulation on the perceived intensity of the neutral faces only when participants received the feedback of the other person’s ratings, by amplifying the perceived neutrality of faces. Taken together, these results suggest that shared attention amplifies the neural processing of faces, regardless of the valence of facial expressions.
Genetic variants affecting the neural processing of human facial expressions: evidence using a genome-wide functional imaging approach