Stimulus predictability and the gap effect on pre-saccadic smooth pursuit

THERE is disagreement in the literature as to whether smooth pursuit latency is reduced when a temporal gap is introduced between the extinction of a central fixation target and the illumination of an eccentric moving target. This study confirms that in human subjects smooth pursuit latency is reduced by gaps and that the magnitude of the reduction is related to the duration of the gap. However, latency is not solely determined either by visual factors or by task parameters such as spatial predictability, but is affected by task context. The results suggest a role for non-visual factors such as attention in the initiation of pursuit. (C) 1998 Rapid Science Ltd.