Abstract
The smooth pursuit system integrates the motion of stimuli with inconsistent local velocity components to obtain a global velocity vector (Heinen & Watamaniuk, 1998). Since pursuit of a single spot is attentive, it might be expected that the integration process required to pursue global motion would place additional attentional demands on the pursuit system. If so, either pursuit of global motion or simultaneous performance on an attention-demanding task should be compromised. We had observers attentively follow the local elements of a small, multiple object tracking (MOT) stimulus (Pylyshyn & Storm, 1988) that translated across the screen, and simultaneously pursue the global stimulus motion with their eyes. The stimulus was a cloud of 4, 8, or 10 dots that moved randomly within a virtual 10 deg containment region. Observers attentively tracked 0, 2, 4 or 5 target dots respectively from the cloud. The MOT task was performed on the cloud as it translated from left to right at a global speed of 7 deg/sec, or remained at the center of the screen without translational motion. We found that performance on the MOT task was the same with and without pursuit, and decreased as the number of MOT targets increased. Furthermore, pursuit gain was no different when pursuing the cloud with or without the MOT task imposed, and improved as the number of dots increased. With the maximum number of dots, the gain was the same with or without an embedded pursuit target, indicating the elements were integrated with no interference from the attention task. The results suggest that motion integration during pursuit is a relatively inattentive process.
Meeting abstract presented at OSA Fall Vision 2012