Grasping Occam's Razor

Nine years after proposing our "new view on grasping", we re-examine the support for the approach that we proposed. This approach consisted of two steps. The first step was to formulate three assumptions that made it possible to model grasping in the same way as one would model movements of a single digit. The second step was to implement an existing model for movements of a single digit (minimum jerk model) in accordance with these assumptions. In both cases we applied Occam's razor: we used as few entities as possible to explain as many phenomena as possible. Here we evaluate both steps in the light of recent experimental results. We show that there is ample support for assuming that the movement of the fingertip is controlled in the same way in a reach-to-grasp movement as in other movements performed to interact with objects. The predictions based on the implementation of the minimum jerk model were Surprisingly good in many situations, although they were clearly wrong in some other situations. Since more complicated models do not perform better, we conclude that currently our approach gives the best description of grasping.