Humans are remarkably accurate at recognizing familiar faces, even from degraded and novel pictures, while the recognition of unfamiliar faces in different pictures is often prone to error. Researchers therefore propose image-independent representations for familiar but pictorial representations for unfamiliar faces. While differences between familiar and unfamiliar face recognition are easy to demonstrate in behavioral studies, however, cognitive neuroscience has so far largely failed to show a large and robust neural correlate of image-independent familiar face recognition.
In a recent study (Wiese, Tüttenberg, et al., 2019, Psychological Science), we examined event-related brain potentials elicited by highly personally familiar (close friends, relatives) and unfamiliar faces. We presented multiple different “ambient” images per identity, varying naturally in lighting conditions, viewing angles, emotional expressions etc., while participants responded to randomly intermixed pictures of butterflies.
Figure 1. a) Sample “ambient” images and balancing of familiarity across participants. b) Trial structure of the experiment. All images published with permission of the depicted persons.
Familiar faces elicited more negative amplitudes than unfamiliar faces in the N250 time range (200–400 ms), which is considered to reflect the activation of stored face representations. Importantly, an increased (> 4µV) familiarity effect was observed in the subsequent 400-600 ms time range. Similar to N250, this Sustained Familiarity Effect (SFE) had a right-lateralized, occipito-temporal scalp distribution. It was reliably detected in 84% of individual participants, while it was not observed in any participant in a control experiment in which all faces were unfamiliar.
Figure 2. a) Grand average ERP at right occipito-temporal electrode TP10, showing more negative amplitudes for personally familiar than unfamiliar faces, both in the N250 (200-400 ms) and SFE (400-600 ms) time range. b) Scalp-topographical voltage maps, showing the distribution of familiarity effects (unfamiliar – familiar) in the N250 and SFE time range. c) Mean (and 95% CI) difference curve (unfamiliar – familiar) at TP10.
Additional experiments revealed that the SFE is smaller for personally, but less familiar faces (e.g., university lecturers) and absent for pictures of celebrities. Moreover, while the N250 familiarity effect does not strongly depend on attentional resources, the SFE is substantially smaller when participants’ attention is directed away from the face stimuli (Wiese, Ingram, et al., in press, Cortex). We interpret the SFE as reflecting the integration of visual with additional person-related (e.g., semantic, affective) information needed to guide potential interactions. We propose that this integrative process is at the very core of identifying a highly familiar person.
- Wiese H, Ingram BT, Elley ML, Tüttenberg SC, Burton AM, Young AW (in press). Later but not early stages of familiar face recognition depend strongly on attentional resources: Evidence from event-related brain potentials. Cortex.
- Wiese H, Chan CYX, Tüttenberg SC (in press). Properties of familiar face representations: Only contrast positive faces contain all information necessary for efficient recognition. Journal of Experimental Psychology: Learning, Memory, and Cognition.
- Wiese H, Tüttenberg SC, Ingram BT, Chan CYX, Gurbuz Z, Burton AM, Young AW (2019). A robust neural index of high face familiarity. Psychological Science, 30,261-270.