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Talia Retter, Fang Jiang, Bruno Rossion; The speed of human face categorization. Journal of Vision 2018;18(10):356. doi: 10.1167/18.10.356.
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Faces can be discriminated from other objects in the visual environment with astonishing speed (100-150 ms). However, a selective electrophysiological response to faces persists for a relatively long time (over 400 ms) in the human brain (Retter & Rossion, 2016). Here, we determined 1) the minimal stimulus presentation duration required to elicit a face-categorization response; moreover, we investigated 2) the effect of increasing image presentation duration on the amplitude, spatial, and temporal aspects of face-categorization responses, and 3) the relationship of these neural effects with behavioral face categorization responses. We recorded high-density EEG from 16 naïve observers with ascending 63-s series of natural object images at nine presentation durations, from 8 to 333 ms (120 to 3 Hz), throughout which temporally masked faces appeared consistently every 1 s (1 Hz). In a second experiment with the same, debriefed participants, we presented temporally masked faces non-periodically within shorter sequences, each at a constant frequency, with an explicit face detection task. The results showed a significant face-categorization response at 1 Hz emerging with 33-ms of presentation at the group level, varying from 17-83 ms across individual participants. Most importantly, we observed a general increase in the amplitude of the face-categorization response as presentation duration increased, but the correspondence of this effect with behavioral accuracy suggests that lower 1-Hz amplitudes were largely driven by missed detections. Across presentation durations, face-categorization responses displayed similar occipito-temporal topographies and sequences of temporal deflections. Thus, we propose that a face-selective response is mainly all-or-none, occurring occasionally to faces at extremely short viewing times and becoming more consistent, but not more evolved, as presentation duration increases (up to about 50-80 ms). One practical implication of these results is that, at least for measuring face categorization electrophysiologically with young adults, (masked) presentation durations exceeding 80 ms are not required.
Meeting abstract presented at VSS 2018
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