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Carlo Campagnoli, Fulvio Domini; Reach-to-grasp actions affect the perceptual scaling of disparity-defined depth.. Journal of Vision 2014;14(10):407. doi: https://doi.org/10.1167/14.10.407.
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© ARVO (1962-2015); The Authors (2016-present)
In previous studies it has been found that the perceived structure of 3D objects can be affected by non visual factors, such as the observer's reach capability (Volcic et al., 2013). Here we investigate whether an actual motor execution affects perception of 3D structure from binocular disparities. Participants saw a disparity defined three-rod configuration in which a central rod was in front of two flanking rods located at the same depth plane (orthogonal to the sagittal plane), so to form an isosceles triangle with the apex centered along the line of sight. In a 2AFC task subjects were asked to judge whether this triangle was deeper or shallower than an equilateral triangle. The depth of the triangle (i.e. the depth separation between the front rod and the flanking rods) was varied across trials with a staircase procedure, allowing us to determine the value at which each participant perceived an equilateral triangle. In two separate blocks participants either simply looked at the three-rod configuration (Visual condition) or reached to grasp it before making the perceptual judgment (Motor condition). The reach-to-grasp action did not provide any additional information about the depth or location of the three-rod configuration, since subjects could neither see their hand of feel the object. The order of the two blocks was counterbalanced across subjects. We found that (1) the three-rod configuration appeared shallower in the Motor condition than in the Visual condition and (2) subjects who performed the Motor condition first perceived the depth of the triangle in the Visual condition as shallower than subjects who performed the Visual condition first. These results indicate that a reach-to-grasp action affects perceived disparity defined depth, suggesting that uninformative proprioceptive signals influence the scaling of binocular disparities. Surprisingly this influence lasts well after proprioceptive signals are no longer available.
Meeting abstract presented at VSS 2014
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