Prehension is really reaching and grasping
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Updated: Jul 14, 2026

Frame-by-Frame Video Analysis of Idiosyncratic Reach-to-Grasp Movements in Humans
Published on: January 15, 2018
Cornelis van de Kamp1, Frank T J M Zaal
1Center for Human Movement Sciences, University of Groningen, PO Box 196, 9700 AD Groningen, The Netherlands.
Abstract:
Prehension has traditionally been seen as the act of coordinated reaching and grasping. However, recently, Smeets and Brenner (in Motor Control 3:237-271, 1999) proposed that we might just as well look at prehension as the combination of two independently moving digits. The hand aperture that has featured prominently in many studies on prehension, according to Smeets and Brenner's "double-pointing hypothesis", is really an emergent property related to the time course of the positions of the two digits moving to their respective end points. We tested this double-pointing hypothesis by perturbing the end position of one of the digits while leaving the end position of the opposing digit unchanged. To this end, we had participants reach for and grasp a metallic object of which the side surfaces could be made to slide in and out. We administered the perturbation right after movement initiation. On several occasions, after perturbing the end position of one digit, we found effects also on the kinematics of the opposing digit. These findings are in conflict with Smeets and Brenner's double-pointing hypothesis.
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