Humans are remarkably accurate at recognising familiar faces, while their ability to recognize, or even match, unfamiliar faces is much poorer. However, previous research has failed to identify neural correlates of this striking behavioural difference. Here we show a clear difference in brain potentials elicited by highly familiar faces versus unfamiliar faces. This effect starts 200 ms after stimulus onset and reaches its maximum at 400-600 ms. This Sustained Familiarity Effect is substantially larger than previous candidates for a neural familiarity marker and is detected in almost all participants, representing a reliable index of high familiarity. While its scalp distribution is consistent with a generator in the ventral visual pathway, its modulation by repetition and degree of familiarity suggests an integration of affective and visual information.

The authors gratefully acknowledge help during stimulus preparation and EEG recordings by Zehra Gurbuz, Malina Hobbie, Brandon Ingram, Maka Julios-Costa, Klaudia Saar and Wiebke Struckmann. We are thankful to Prof Vicki Bruce for repeated discussions of the contrast chimera effect, which have inspired the experiments reported here. The studies presented here used scripts provided by M.J. Smithson (http://www.michaelsmithson.online/stats/CIstuff/CI.html).