Effects of task goal on movement kinematics and line bisection performance in adults without disabilities.

Abstract

This study investigated (a) whether the kinematic profile of a reaching-for-an-object movement would differ depending on the goal of the reaching task and (b) the effect of task goal on attentional carryover. Twenty-four adults without disabilities performed a horizontal line bisection task under three conditions: (a) a natural condition (pressing the ringing lever of a desk bell), (b) an impoverished condition (touching the ringing lever of a desk bell), and (c) a control condition (bisecting a line only). Only the natural and impoverished conditions used the reaching task (i.e., pressing or touching the ringing lever of the desk bell). The kinematic profile of reaching for the bell was established with the OPTO-TRAK system, a quantitative kinematic analysis measure. The line bisection task was performed immediately after the reaching task, which was located adjacent to the left of the line to be bisected. The natural condition elicited better quality of reaching movement than did the impoverished condition. It produced significantly shorter movement time and higher peak velocity. A less impressive effect was found for percentage of reach where peak velocity occurs. Bisection performance under the two experimental conditions was leftward biased relative to the control condition, and the magnitude of leftward bias in the natural condition was greater than that for the impoverished condition. Results supported one core assumption of occupational therapy: goal-directed and functional tasks can be used to enhance human performance. If the results hold for clinical populations, manipulations of functional goals may enhance movement performance of persons with disabilities and remediate left neglect often seen in clients who have had a stroke.