Pinhole viewing strengthens the Hollow-Face Illusion H Hill, T Koessler |
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School of Psychology, University of Wollongong, Australia
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| The hollow-face illusion is the perception of a concave mask as a convex face when seen from beyond a certain distance. While a real three-dimensional mask is seen as concave at close distances, this is rarely if ever the case for frontal photographs or video of such masks. This suggests that monocular image information alone is insufficient to disambiguate depth. How is it that a three-dimensional mask is seen as concave at close distances when viewed monocularly? Here we tested whether ocular accommodation contributes by manipulating its availability using pinhole glasses. Pinhole viewing increased the distance over which the mask is seen as concave for both monocular and binocular viewing. This is consistent with accommodation disambiguating depth. This effect of pinholes alone was greater than that of monocular viewing alone and closing one eye had no additional effect when wearing pinholes. This suggests vergence may also disambiguate depth at short distance and be disrupted by pinhole viewing. Additional tests investigated the perceived flatness and distance of the illusory face. Observers reported that the illusion appeared more pronounced in depth when viewed through pinholes but that binocularity had no effect on this percept. Apparent distance was affected by both manipulations. |
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