The effects of dividing attention on smooth pursuit eye tracking.

Attentional processes have traditionally been closely linked to the production of saccadic eye movements, but their role in the control of smooth pursuit eye movements remains unclear. In two experiments we used dual task paradigms to vary the attentional resources available for pursuit eye tracking. In both experiments we found that attentionally demanding secondary tasks impaired smooth pursuit performance, resulting in decreased velocity and increased position error. These findings suggest that attention is important for the maintenance of accurate smooth pursuit, and do not support the hypothesis that pursuit is a relatively automatic function that proceeds optimally in the absence of attentional control. These results add weight to the suggestion that a similar functional architecture underlies both pursuit and saccadic eye movements.