August 2012
Volume 12, Issue 9
Vision Sciences Society Annual Meeting Abstract  |   August 2012
The markedly greater sensitivity to nonaccidental vs. metric shape properties is not reflected in HMAX calculation of shape similarity
Author Affiliations
  • Ori Amir
    Psychology, University of Southern California
  • Irving Biederman
    Psychology, University of Southern California\nNeuroscience, University of Southern California
Journal of Vision August 2012, Vol.12, 1054. doi:
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      Ori Amir, Irving Biederman; The markedly greater sensitivity to nonaccidental vs. metric shape properties is not reflected in HMAX calculation of shape similarity. Journal of Vision 2012;12(9):1054.

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      © ARVO (1962-2015); The Authors (2016-present)

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Nonaccidental properties (NAPs) are image properties that are invariant over orientation in depth and are distinguished from metric properties (MPs) that can change continuously with variations over depth orientation. To a large extent the presence of NAP differences are what allow facile recognition of objects at novel viewpoints. Two match-to-sample experiments with 2D or 3D appearing geons assessed sensitivity to NAP vs. MP differences. A matching geon was always identical to the sample and the distractor differed from the matching geon in either a NAP or an MP on a single generalized cone dimension. For example, if the sample was a cylinder with a slightly curved axis, the NAP distractor would have a straight axis and the MP distractor would have an axis of greater curvature than the sample. Critically, the NAP and MP differences were scaled so that the MP differences were slightly greater according to pixel energy and Gabor wavelet measures of dissimilarity. Exp. 1 used a staircase procedure to determine the threshold presentation time required to achieve 75% accuracy. Exp. 2 used a constant, brief display presentation time with reaction times and error rates as dependent measures. Both experiments revealed markedly greater sensitivity to NAP over MP differences (e.g., 2X the NAP exposure duration required for MPs to reach 75% accuracy in Exp. 1), and this was generally true for the individual dimensions. The NAP advantage was not reflected in the similarity computations of the C2 stage of HMAX, a widely cited model of later ventral stream processing. The C2 output depicted greater dissimilarity to MPs, in contrast with the psychophysical results.

Meeting abstract presented at VSS 2012


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