TEMPORAL AND SPATIAL COUPLING OF POINT OF GAZE AND HAND MOVEMENTS IN AIMING

Temporal and spatial coordination of both point of gaze (PG) and hand kinematics in a speeded aiming task toward an eccentrically positioned visual target were examined with the Optotrak 3D movement analysis sy stem in tandem with the ASL head-mounted eye tracker. Subjects (N = 10 ) moved eyes, head, hand, and trunk freely. On the majority of trials, the PG pattern was a large initial saccade that undershot the target slightly, then 1 or more smaller corrective saccades to reach the targ et. The hand exhibited a similar pattern of first undershooting the ta rget and then making small corrective movements. Previously (W. F Hels en, J. L. Starkes, & M. J. Buekers, 1997), the ratio of PG and total h and response time (50%) was found to be an invariant feature of the mo vement. In Line with those results, a striking temporal coupling was f ound between completion of the primary eye saccade and time to peak ac celeration for the limb. Spatially, peak hand velocity coincided with completion of 50% of total movement distance. Those findings support a 2-component model of limb control.