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Cristina de la Malla, Jeroen Smeets, Eli Brenner; Errors in manual interception are precisely what one would expect for the psychophysically determined errors in perception. Journal of Vision 2017;17(10):19. doi: https://doi.org/10.1167/17.10.19.
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Visual illusions influence the way we perceive things. They can also influence the way we move. Whether illusions influence perception and action to the same extent is still under debate. A major difficulty in resolving this debate is that it only makes sense to compare the influences if one knows how the action is based on the attribute that is influenced by the illusion. We therefore used what we know about how visual information guides the hand in interception to examine whether psychophysical estimates of the extent to which a two-dimensional Gabor patch (a sinusoidal grating
of which the luminance contrast is modulated by a two-dimensional Gaussian) is perceived to move at a different velocity than its true velocity when the grating moves within the Gaussian can explain the errors that people make when trying to intercept such Gabor patches. In separate two-interval forced choice discrimination tasks we measured how moving the grating influenced the perceived position and the perceived velocity of the target. When the grating moved in the same direction as the patch, the patch was judged to move faster than it really was. When it moved in the opposite direction, it was judged to move more slowly. The perceived position was hardly affected. We calculated the errors that subjects
would make if they used these judgements to predict the motion of the moving patch during the
last 100 ms of an interceptive action (when movements can no longer be corrected due
to sensorimotor delays). We compared these predicted errors with the errors that subjects actually made when they had to intercept similar targets. The predicted errors closely matched the actual errors in interception. We conclude that errors in perceiving how a target moves lead to the errors that one would expect in an action directed towards such targets.
Meeting abstract presented at VSS 2017
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