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Young-Lim Lee, Geoffrey P. Bingham, J. Farley Norman, Charles E. Crabtree; Calibration of shape perception used to guide reaches-to-grasp. Journal of Vision 2005;5(8):122. doi: https://doi.org/10.1167/5.8.122.
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In this study, the use of shape perception to guide reaches-to-grasp objects was investigated. The goal was to determine whether shape perception could be calibrated in this context. The participants reached to grasp cylindrically-shaped objects so as to span either the width or the depth with their index finger and thumb. The trajectory of reaching and grasping was measured and the terminal grasp aperture (TGA) was used to evaluate use of perceptual information. TGA occurs at the end of a reach but before the hand has contacted an object. In Experiments 1 and 2 (baseline data), we investigated whether occluding vision of the hand would affect reaches-to-grasp object width or depth. The results showed that TGA varied reliably with width and depth, and there was no effect of the occluded hand. Normally, one reaches to grasp width or depth, not width then depth. In Experiment 3, we investigated whether TGA covaries with width and depth when width and depth are grasped successively in a single reach. The results showed that they did. Experiment 4 replicated Experiment 3 with the addition of random probe trials in which participants grasped virtual objects (no actual contact). The results showed that such probe trials were the same. In Experiment 5, we investigated whether use of perceived shape could be recalibrated by distorted haptic feedback. Participants were given progressively distorted haptic feedback about shape and recalibration was tested by probe trials.
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