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Eshed Margalit, Xiaomin Yue, Irving Biederman; Impaired Face and Non-face Discrimination by Developmental Prosopagnosics (DPs). Journal of Vision 2016;16(12):1251. doi: 10.1167/16.12.1251.
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Developmental prosopagnosics (DPs) present no lesions nor have a history of compromised neural functioning. Given that their activation of face-selective cortex is normal, it is surprising that their capacity to perceptually discriminate faces and non-face objects has never been rigorously assessed. Normal discrimination of faces would suggest that the underlying deficit might not be a consequence of a poor perceptual representation but, instead, difficulty in matching a well-defined representation to stored representations in memory. If a deficit in discriminating faces is observed, is it also manifested when discriminating non-face stimuli that differ along the same underlying physical attributes as faces and to an equivalent extent as the faces? 7 DPs and 53 controls performed a match-to-sample task (Fig. 1) in which they viewed a triangular display of either three faces or three blobs (harmonics of a sphere resembling teeth). The stimulus on the top of the display was the sample and one of the two base stimuli was an exact match to the sample with the non-matching foil differing metrically from the sample. Like the faces, the blobs were smoothly sculptured in 3D and had face texture (Portilla & Simoncelli, 2000) projected onto their visible surfaces. The subject responded by pressing the arrow key on the side of matching stimulus. The similarity of the foil to the matching stimulus was scaled according to the Gabor-jet model of V1 similarity that predicts psychophysical similarity of both faces and blobs almost perfectly (Yue et al., 2012). Importantly, the scaled distributions of dissimilarities of foils to matching stimuli were almost identical for faces and blobs. DPs were slower and less accurate than controls in discriminating both faces and blobs (Fig. 2) with their deficits approximately equivalent for both faces and blobs, suggesting a general deficit in discriminating metric variations.
Meeting abstract presented at VSS 2016
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