Influence of global motion onset on goal-directed eye movements.

Saccades are very rapid eye movements in between two phases of fixation, which offer a precise measure of behaviour for the direction of the spotlight of attention. The onset of global motion is known to attract our attention reflexively. We asked whether brief global motion stimuli are able to modify the execution of saccades. When participants performed visually guided saccades towards a target presented in front of a structured background, saccade latency was 174 ms on average and correctness of saccades was 100%. If the presentation of the target occurred at the same time as the onset of a brief global motion signal, then the saccade latency increased dramatically to 243 ms with a slight decrease in correctness to 89%. However, if the motion stimulus preceded the presentation of the target, then the latency decreased to 114 ms while the correctness dropped close to chance levels (62%).