Emotional distractors modulate event-related potentials even at very low contrast levels

Emotional visual stimuli, whether appealing or aversive, preferentially capture exogenous attention due to their evolutionary significance. This study assessed whether such capacity persists at low contrast levels, where stimuli are minimally perceived. To this end, we recorded behavioral and electrophysiological (event-related potentials, ERPs) indices of attentional capture from 38 participants who were exposed to negative, neutral, and positive scenes, each presented at four distinct contrast levels. These contrast levels had previously resulted in a correct recognition rate of 49%, 52%, 58%, and 66% (chance = 50%) in a previous sample of 144 participants. Participants were presented with these scenes as distractors while simultaneously performing a perceptual task involving line orientation discrimination. ERP results revealed an emotional effect persistent across all contrast levels. Specifically, occipito-parietal P1 (88–119 msec) was larger for negative than for positive distractors, more intensely for the lowest contrast, while in a broadly spatially distributed N2 component, positive distractors elicited larger amplitudes relative to both negative (213–354 msec) and neutral (213–525 msec) images. While emotional valence did not influence behavioural measures, overall performance deteriorated as contrast increased. These findings suggest stimuli captured exogenous attention, and reinforce the advantage of emotional distractors in accessing neural processing automatically and highlight the existence of a temporal negativity bias. Importantly, our novel findings emphasize the robustness of this pattern, present even under limited perceptual conditions.