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Faces with emotional information–by virtue of their expression or their history of affective learning–are prioritized during neuronal processing as compared to neutral faces. Classical conditioning studies have shown that aversively conditioned (CS+) faces potentiate different face processing stages as evidenced by increased early and late event-related potential (ERPs) components. However, it is unknown whether and how ERP modulations depend on certain attentional conditions. To examine this question, this preregistered study investigated ERPs to faces paired with aversive screams or neutral sounds under three tasks with increasing attention to CS + relevant features of the face: Participants (N = 40) had to discriminate either the orientation of superimposed lines, perceived gender, or the CS association. We found potentiation of the N170, the Early Posterior Negativity (EPN), and, most remarkably, the Late Positive Potential (LPP) to CS + faces regardless of task condition. This finding suggests that, in contrast to other types of emotional information and learning, classical conditioning boosts early and late processing stages, even if no explicit attention to the face information or the CS association is required.

Paying attention to faces is of special interest for humans as well as for scientific research. The experimental manipulation of facial information offers an ecologically valid approach to investigate emotion, attention and social functioning. Humans are highly specialized in face perception and event-related brain potentials (ERP) provide insights into the temporal dynamics of involved neuronal mechanisms. Here, we summarize ERP research from the last decade, examining the processing of emotional compared to neutral facial expressions along the visual processing stream. A particular focus lies on exploring the impact of attention tasks on early (P1, N170), mid-latency (P2, EPN) and late (P3, LPP) stages of processing. This review systematizes facial emotion effects as a function of different attention tasks: 1) When faces serve as mere distractors, 2) during passive viewing designs, 3) directing attention at faces in general, and 4) paying attention to facial expressions. We find fearful and angry expressions to reliably modulate the N170, EPN, and LPP component, the latter benefiting from attention directed at the emotional facial expression.