N400 is a cortical potential measured on lateral-occipital and central-parietal electrodes typically in tasks when a word does not fit into an otherwise meaningful sentence. Matching semantic content, however, is also a crucial process during face recognition, when visual features have to be paired with consciously accessible semantic information. Previous research has shown that mismatched stimuli impose a cognitive load on face recognition, and therefore increase response time. In addition, the amplitude of the N400 component increases proportionally with semantic mismatch, regardless of stimulus modality. Generally, N400 can also be measured in stereotype-inconsistent situations. The question is whether this effect can be detected in a face recognition task and whether the magnitude of semantic mismatch affects reaction times and the amplitude of N400.

We pre-measured the semantic distance between occupational labels. Participants learned to recognize faces that were stereotypically matched to these. In the recognition task the faces were preceded by different types of priming stimuli: either with the original label (congruent condition) or with an incorrectly paired label (incongruent conditions). The task was to press different response buttons depending on whether they have seen the face before or not.

We found that in the presence of a mismatched stimulus, both N400 amplitude and RT increased. The larger the representational distance between the learned and the presented labels, the larger was the amplitude of the N400. This implies that semantic matching is a decisive process in face recognition, and evoked cortical potentials reflect a general underlying mechanism of information recollection.