In this paper we present a method for studying human selection of fingertip contact point locations during grasping and manipulation. Our aim is to perform a functional analysis, looking at how a particular choice of contact point distribution affects the subjects' ability to resist external forces applied to the grasped object. We rely on grasp quality metrics derived from the Grasp Wrench Space, a method traditionally used for quantifying robotic grasps. We illustrate this approach by studying human grasps of a spherical object under a number of different disturbances. Our results indicate that the quality metrics we use can help explain the subjects' choice of contact points, although other possible grasping strategies may exist.