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Alen Hajnal, Jeffrey Wagman, David Bunch, Jonathan Doyon; Do Geographical Slants Feel Steeper Than They Look? . Journal of Vision 2014;14(10):1357. doi: 10.1167/14.10.1357.
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Kinsella-Shaw, Shaw, and Turvey (1992) have shown that nonvisible surface slant perceived haptically by foot is matched with visually perceived slant by a factor of 0.81. Hajnal, Abdul-Malak, and Durgin (2011) have demonstrated that the same slope perceived visually without standing on it appears shallower than when stood on without looking. We asked participants to judge whether they would be able to stand on a ramp. In the first experiment, visual inspection was compared with trials in which participants took half a step with one foot onto an occluded ramp. Visual perception closely matched the actual maximal slope angle that one could stand on. However, the maximum slope angle based on perception by foot was significantly lower. We suspected that the additional balance task of standing on one foot might cause distortion in haptic perception. In the second experiment we repeated the same except that participants sat in a chair. This manipulation resulted in no differences between modalities, and a perfect match between perception and action capabilities. In the third experiment we offered a direct test of whether balance may cause a split between vision and haptics, by having participants hold onto a sturdy tripod while standing on one foot in the haptic condition. We obtained the same modality differences as in the first experiment. This led us to conclude that differences in the range of motion at the ankle and knee joints may play a role in pedal perception. The range of motion is larger while sitting down compared to when standing, thus potentially causing distortion of haptic perception. Implications for ecological theory (Gibson, 1979) will be offered by discussing the need for multisensory integration, instead of nonrepresentative comparisons of modalities tested in isolation.
Meeting abstract presented at VSS 2014
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