The present reaction on the paper of Smeets and Brenner focuses on two premises of their proposed model The first is that grasping is nothing more than pointing with two fingers. It is argued that this assumption cannot be upheld in light of the differences between both actions with respect to neuromuscular structures, muscular innervation, use of visual feedback, and basic function The second premise of the model is that the velocity profile of the transport component is symmetrical and independent of intrinsic object properties. It is shown that the symmetrical velocity profile represents a boundary condition and is influenced by intrinsic object properties. Given these concerns, it is doubtful that the model in its present form will add much to our understanding of the control of grasping.
Bert Steenbergen is with the Innovation Centre, Werkenrode, P.O. Box 9002 6560 GC Groesbeek, The Netherlands. He is also with the University of Nijmegen.