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Marissa Nederhouser, Michael C. Mangini, Kazunori Okada; Invariance to contrast inversion when matching objects with face-like surface structure and pigmentation. Journal of Vision 2003;3(9):93. doi: 10.1167/3.9.93.
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© ARVO (1962-2015); The Authors (2016-present)
There is a marked cost in face matching performance when members of a sequentially presented pair of faces differ in contrast polarity, i.e., reversal of luminance, but no such costs are apparent when matching objects (Subramaniam & Biederman,1997). This result holds true even when the faces and chairs, on different trials, are of equal similarity, as assessed by a Gabor-jet similarity measure. Unlike face matching, object matching can generally be accomplished by using differences in parts and nonaccidental shape properties defined by edges that would be unaffected by changes in contrast polarity. Would object recognition remain invariant when such differences were not available?
Subjects performed a match-to-sample forced-choice task on smooth, blobby volumes generated by varying the amplitudes of the 2nd & 3rd harmonics of a sphere. These stimuli did not resemble faces although their discrimination was presumed to require the same type of information as that for faces. In Exp.1, their discrimination required matching the objects based on fine differences in surface curvature. In Exp.2, the subjects could also use pigmentation information in the form of a constrained set of high contrast patches. Stimulus pairs in trials spanned a large range of similarity, comparable to both faces and objects.
Both expert and novice performance on these tasks was examined, as well as that of a prosopagnosic. Differences in contrast between stimuli resulted in no costs in stimulus matching, for experts and novices, throughout the range of similarity. The experts had markedly lower RTs and error rates than the novices, even on a new configuration of stimuli, indicating a transfer of expertise. The extremely poor performance of the prosopagnosic suggests that the discrimination of these stimuli might engage the same processing as that involved in faces. These results suggest, as did our prior studies, that faces are special with respect to the costs of contrast reversal.
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