Control of reflexive and voluntary saccades in the gap effect

In two experiments, we examined whether voluntary and reflexive saccades sh ared a common fixation disengagement mechanism. Participants were required to perform a variety of tasks, each requiring a different level of informat ion processing of the display prior to execution of the saccade. In Experim ent 1, participants executed either a prosaccade or an antisaccade upon det ecting a stimulus array. In Experiment 2, participants executed a prosaccad e to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the remova l of the fixation stimulus and the onset of the stimulus array. In both exp eriments, it was found that saccadic latencies were shortest when the fixat ion stimulus was removed before the onset of the stimulus array-a gap effec t. It was concluded that reflexive and voluntary saccades share a common fi xation disengagement mechanism that is largely independent of higher level cognitive processes.