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Federica Biotti, Richard Cook; Evidence for opponent coding of hand-identity within a multidimensional 'hand-space'. Journal of Vision 2014;14(10):826. doi: https://doi.org/10.1167/14.10.826.
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© ARVO (1962-2015); The Authors (2016-present)
In recent years there has been much speculation that facial identities are represented within a multidimensional 'face-space'. According to this framework, the perception of facial identity is determined by the relative excitation of opponent cortical populations, tuned to complementary facial attributes. Consistent with this view, adapting to a particular facial identity systematically biases perception towards its anti-face – the corresponding identity on the opposite side of the population mean. Using a psychophysical adaptation procedure, the present study sought to determine whether exemplars of other body parts are also represented relative to an average, within a multidimensional space. Fifty images of male hands were first described in terms of their shape and texture variation and then subjected to principal components analysis (PCA). Two pairs of anti-hands were subsequently created by reconstructing hand identities corresponding to ±2 standard deviations along the axes defined by the odd and even principal components comprising the computed "hand-space." These 4 images were used as adapting stimuli in an adaptation procedure. Trials presented an adapting stimulus for 10 seconds, followed immediately by a test stimulus, presented for 1 second, taken from either a congruent or orthogonal morph continuum. Observers made binary-choice judgments about the identity of the test hand. Perceptual bias was inferred from the point of subjective equivalence (PSE) on the resulting psychometric functions. Adapting to a particular hand identity was found to selectively bias perception of subsequently viewed test stimuli in the direction of the anti-hand. No systematic bias was detected in the orthogonal direction. These results are analogous to similar findings with facial identity and accord with recent suggestions that faces and bodies may recruit similar perceptual mechanisms.
Meeting abstract presented at VSS 2014
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