The time course of presaccadic attention shifts.

The dynamics of the allocation of attention during the preparation of saccadic eye movements was studied in a dual task paradigm. As the primary task, participants had to perform a saccade to letter-like items arranged on a clock face. The secondary task was a 2AFC discrimination task in which a discrimination target (DT) ('E' or '3') was presented among distractors, either at the saccade goal, or at a spatially separate, precued location. In the first experiment, the position of the DT was kept constant within an experimental block, while the saccade target location varied. In the second experiment, the location of the DT was varied while the saccade target remained the same within a block. The data demonstrate that attentional dynamics differs between the experiments--attention can shift to the saccade goal early or late during the saccade preparation period, depending on the task. Immediately before saccade onset, however, discrimination performance at the location of the saccade target is always superior to other locations, arguing for a strict and selective coupling between saccade preparation and attention.