When moving to grasp an object having adjacent obstacles that limit the space available for placing the fingers, the time for the reach/grasp is dependent on the distance of reaching and the space available for finger placement. Here we model the time taken in terms of these variables and develop mathematical models for the reach and grasp phases of the task and the location of obstacles. Data show that the movement to the target may be made under visual control and that, when the obstacles are close to the target object, a visually-controlled movement is made that is modeled by a modified form of Fitts' law. The time for the two components of the reach/grasp appear to be independent and linearly additive.
Keywords: grasping; models of movement; obstacle avoidance; prehension; reaching.