Hand Use Preferences in Delimiting the Boundaries of Normal Working Area

Abstract

Geometric models of normal working area have been derived from analyses of theoretically possible, but contrived and restrictive arm and hand movements (Farley, 1955; Squire, 1959; Wang et al., 1999). It is unclear whether the resulting boundaries delimit a safe, comfortable and effective reach area. The goal of the current investigation was to obtain data that can establish reach boundaries that reflect actions that are both comfortable and efficient. Adults reached for objects placed in various directions and distances in front of them. The type of reach action used to pick up the object was categorized in an effort to demarcate reach envelopes for different reach actions and identify the directional location in the workspace at which people change from reaching with their right hand to using their left hand. These data showed that people's reach actions violated important characteristics of the geometric models, including the spatial symmetry in the use of the right and left hands. From these data we are able to construct “performance-based” models of workspace area.