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Richard Cook, Clarisse Aichelburg, Punit Shah, Alan Johnston; Perceptual interactions between dynamic facial features . Journal of Vision 2014;14(10):564. doi: https://doi.org/10.1167/14.10.564.
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© ARVO (1962-2015); The Authors (2016-present)
We are frequently exposed to correlated eye and mouth movements such as the characteristic changes accompanying yawning, sneezing or laughing. However, it is not clear whether the visual system is sensitive to these dynamic regularities, encoding facial behavior relative to a set of dynamic global expression prototypes, or whether it simply forms a piecemeal description of feature states over time. We sought to address this question by looking for evidence of perceptual interactions between dynamic facial features. Participants viewed two avatar faces side-by-side, a standard and a comparison stimulus. Both faces opened and closed their eyes periodically at 1.25 Hz. The mouth on the comparison stimulus remained closed throughout. The eyelid transitions (open-to-closed and vice versa) exhibited by the standard stimulus always lasted 140 ms. Eyelid transitions for the comparison stimulus varied in duration from 20 ms to 260 ms in steps of 40 ms. Participants were asked to report whether the standard or comparison blinked faster. The perceived speed of the standard eyelid transition was inferred from the point of subjective equality (PSE) on the resulting psychometric function. Perceived speed was measured both upright and inverted, at four relative phase relationships. The presence of the mouth movements caused illusory slowing of the eyelid movements, but only when the standard face was presented upright at 180째 and 270째 phase relationships. Subsequent experiments demonstrate i) that illusory slowing of the eyelids is produced by mouth movements with both sinusoidal and constant velocity kinematic profiles; ii) that the presence of eyelid motion also causes illusory slowing of mouth movements; iii) that individuals with autism spectrum disorders are not susceptible to the illusory slowing. Perceptual interactions between facial features reveal face-specific encoding mechanisms that integrate dynamic features into expression prototypes, encompassing global properties of facial change.
Meeting abstract presented at VSS 2014
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