Mean emotion from multiple facial expressions can be extracted with limited attention: Evidence from visual ERPs

Human observers can readily extract the mean emotion from multiple faces shown briefly. However, it remains currently debated whether this ability depends on attention or not. To address this question, in this study, we recorded lateralized event-related brain potentials (i.e., N2pc and SPCN) to track covert shifts of spatial attention, while healthy adult participants discriminated the mean emotion of four faces shown in the periphery at an attended or unattended spatial location, using a cueing technique. As a control condition, they were asked to discriminate the emotional expression of a single face shown in the periphery. Analyses of saccade-free data showed that the mean emotion discrimination ability was above chance level but statistically undistinguishable between the attended and unattended location, suggesting that attention was not a pre-requisite for averaging. Interestingly, at the ERP level, covert shifts of spatial attention were captured by the N2pc and SPCN components. All together, these novel findings suggest that averaging multiple facial expressions shown in the periphery can operate with limited attention.