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Aviad Ozana, Tzvi Ganel; The contributions of visual and tactile cues to analytic processing during grasping. Journal of Vision 2017;17(10):461. doi: 10.1167/17.10.461.
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© ARVO (1962-2015); The Authors (2016-present)
Visually-guided actions toward real objects are characterized by distinguishable hand gestures. For example, finger kinematics during grasping violate Weber's law, a basic relative principle of visual perception, which implies that visuomotor control is governed by analytic processing of object size. Unlike for real objects, movement trajectories toward 2D line drawings of objects adhere to Weber's law. It can be argued therefore, that when actions are directed to 2D objects, the visuomotor system fails at operating in its normal analytic processing style and is distracted by irrelevant perceptual information. Here, we studied the visual and tactile cues that enable analytic processing during grasping. In Experiment 1, we tested the role of richness in pictorial details. To this purpose, visually-guided actions directed toward 3D objects were compared with actions directed toward high resolution photos of the objects. As for line drawings, actions directed at photos adhered to Weber's law, suggesting that richness in visual details does not contribute to analytic processing. In Experiment 2, we tested the role of tactile feedback from the object. Participants were asked to direct grasping movements toward real objects placed beyond a glass. Grasping movements were terminated with touching the glass flat surface. Surprisingly, although tactile feedback was denied, grasping was still performed in a normal, analytic manner, violating Weber's law. This indicates that tactile feedback is not necessary for analytic processing. In Experiment 3, a similar apparatus was used, but now participants were asked not to touch the glass surface at the end of the movement. Grasping trajectories now adhered Weber's law. Taken together, these findings suggest that analytic processing during grasping does not depend on tactile feedback from the object. Indeed, visual presentation of 3D objects combined with uninformative haptic information from touching a flat surface are sufficient to enable effective analytic processing during grasping.
Meeting abstract presented at VSS 2017
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