Fig. 3.

Criterion for determining the return to fixation. Horizontal eye position (thin trace) and velocity (heavier trace) from a visual trial to a target located at (18°,0°) are plotted as a function of time. Thehorizontal dotted line illustrates the fixation criterion. The vertical dotted line, drawn at the point at which the velocity trace intersects the fixation criterion line, illustrates the return to fixation. Final eye position is defined as the position at the time of return to fixation.