Tradeoff between response speed and pursuit accuracy.

We examined simple and choice reaction times (RTs) to a visual target that appears during smooth pursuit. Participants pursued a moving fixation stimulus accurately before a target stimulus was presented either above or below the fixation stimulus. In the simple RT task, the participants responded to the onset of the target as soon as possible. In the choice RT task, they indicated the target position, i.e., above or below the fixation stimulus, as soon and as accurately as possible. The results showed that, in both tasks, the RTs during smooth pursuit at 10 degrees /s were longer than those during stationary fixation, and the RTs decreased as the fixation stimulus velocity further increased to 40 degrees /s. Since pursuit gains (the ratio of eye velocity to fixation stimulus velocity) decreased as the fixation stimulus velocity increased, these results suggest that there is a tradeoff between pursuit accuracy and RT.