How perceived object dimension influences prehension

A kinematic study assessed the effects of the perceived dimensions of an object upon the patterning of a prehension movement involving that object. If an apple was perceived as two-dimensional, subjects utilized a large precision grip between the index finger and thumb. If the apple was perceived as three-dimensional, whole hand prehension involving all the digits was utilized. A visual perturbation from perceived two-dimensional to three-dimensional at movement onset resulted in a transition from the 2D precision grip pattern to the 3D whole hand prehension. These results suggest that visual mechanisms for interpreting the dimensions of an object directly influence motor selection pathways, and do not necessarily access a three-dimensional central nervous system representation of the object.