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Éric McCabe, Alan Chauvin, Daniel Fiset, Martin Arguin, Frédéric Gosselin; The use of spatial frequency through time in face identification. Journal of Vision 2005;5(8):988. doi: 10.1167/5.8.988.
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© ARVO (1962-2015); The Authors (2016-present)
Face perception has received much attention since it became obvious that something special characterizes this stimulus class (e.g. Bodamer, 1947; Farah et al., 1998 ; Yin, 1969). One promising avenue for the study of face perception involves psychophysical procedures that can determine the information effectively used by human observers. Here we studied the effective use of spatial frequency information through time in face identification using Bubbles (Gosselin & Schyns, 2001; Vinette, Gosselin & Schyns, 2004). We submitted five subjects to 3000 dynamic grayscale faces (6 × 6 deg of visual angle × 180 ms) sampled by dot multiplying their Fourier spectrum with a 2D white Gaussian noise convolved with a Gaussian function (Std's = 0.156 of the Nyquist frequency and 79 ms). The subjects performance was maintained at 75% of correct identifications by adjusting, on a trial by trial basis, the surface under the sampling noise. Using multiple linear regression on response accuracy and sampling noise, we revealed that subjects tend to use a narrow band of low spatial frequency (about 5.8 cycles per face) throughout and, from 100 to 150 ms after stimulus onset, a broader frequency band centered on 15.6 cycles per face. These results suggest that face identification occurs in a two-step process : an initial sweep mainly interested in low spatial frequencies and a later one focussing on mid to high spatial frequencies, which appears particularly important for the efficient resolution of the perceptual task. This two-sweep process is compatible with the proposal of Liu, Harris and Kanwisher (2002) that face identification at an individual level follows a more global categorization of the stimulus as a face. Results are also in agreement with studies that showed a natural bias in face perception for spatial frequencies between 5.62 and 22.5 cycles per face (e.g. Nasanen, 1999; Schyns, Bonnar & Gosselin, 2002 ; Vuilleumier et al., 2003).
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