Attention modulation of rapid face identity discrimination

Abstract

The human face bears prominent biological and social significance and can be detected quickly and automatically (as early as 100ms after presentation; Crouzet et al., 2010). By contrast, it has been suggested that face identity processing could be modulated by selective attention (Palermo & Rhodes, 2007). Our study used a fast periodic visual stimulation approach to examine the effect of selective attention on face identity discrimination at a glance. We recorded 128-channel EEG while participants viewed 70s sequences of female faces shown at 6 Hz. Within each sequence, a randomly selected identity was repeated (A) with different female face identities (B, C…) embedded every 7th image (AAAAAABAAAAAAC…). Responses at 6 Hz reflect common visual processing of all stimuli, while responses at 0.857 Hz (i.e., 6 Hz/7) reflect face identity discrimination (Liu-Shuang, Norcia, & Rossion, 2014). Participants performed two tasks: (1) on Attend Fixation trials, participants monitored the central fixation cross for color changes (6 targets); (2) on Attend Face trials, participants responded to male faces which randomly replaced an oddball female face identity change (6 targets). Although there were robust face discrimination responses in the orthogonal task as shown previously (Liu-Shuang et al., 2014), attending to face gender increased responses on all electrodes, including the bilateral occipito-temporal regions. In order to avoid participants noticing the periodic identity change of every 7th female image, because male target faces always replaced the oddball female faces, in Experiment 2 we randomly embedded the male target faces during each stimulation sequence (replacing either a base face or an oddball face stimulus). However, we found the similar results to experiment 1. Thus, it appears that selective attention can modulate face identity discrimination in a rapid visual stream, but is not mandatory.