Perisaccadic compression in two-saccade sequences.

Around the onset of a saccade toward a target, localization judgments are systematically biased toward the saccade endpoint. This perisaccadic compression is thought to be related to transsaccadic reorganization and due to interfering motor signals in visual maps. It has, however, only been investigated for saccades targeting a single target. Here, we examined whether saccade-sequence programming to stationary target(s) would affect the pattern of localization judgments of a briefly flashed stimulus. We presented saccade targets that could induce either a single saccade or two-saccade sequences and we flashed a bar around saccade onsets. For all two-saccade-sequence conditions, we showed that localization judgments of the stimulus flashed around the first saccade onset are biased toward an intermediate position between the two-saccade landing position, indicating the influence of the second saccade's parallel planning. This implies that motor-planning signals are most likely responsible for perisaccadic compression than motor execution feedback.