Tradeoff between manual response speed and pursuit accuracy revealed by a deadline procedure.

To examine the tradeoff between manual reaction times (RTs) and smooth pursuit accuracy, we manipulated manual RTs to a visual target presented during pursuit by using a deadline procedure that required different response speeds to a target (300, 400, or 500 ms). Participants attempted to pursue a moving row of circles as accurately as possible, while responding to a target within a preset time. Stimulus velocity and target position were manipulated. As the preset time became shorter, participants responded with faster manual RTs and larger pursuit velocity errors, irrespective of the stimulus velocity, indicating a tradeoff between manual RTs and pursuit accuracy. Pursuit velocity errors were also larger after target onset. These results not only suggest that attentional resources as well as spatial shifts of attention play an important role in maintaining accurate pursuit, but also support the notion that a manual RT task is useful for revealing the operation of attention during pursuit.