Saccadic omission revisited: What saccade-induced smear looks like

During active visual exploration, saccadic eye movements rapidly shift the visual image across the human retina. Although these high-speed shifts occur at a high rate and introduce considerable amounts of motion smear during natural vision, our perceptual experience is oblivious to it—a phenomenon known as saccadic omission. Using tachistoscopic displays of natural scenes, we rendered saccade-induced smear highly conspicuous. By manipulating perisaccadic display durations, we studied the dynamics of smear in a timeresolved manner, assessing discrimination performance of smeared scenes, as well as smear amount and orientation. Both measures showed distinctive, U-shaped time courses throughout the saccade, indicating that generation and reduction of smear occurred during saccades. Moreover, low spatial frequencies and orientations parallel to the direction of the ongoing saccade were identified as the predominant visual features accessible in motion smear. We explain these findings using computational models that assume no more than saccadic velocity and human contrast sensitivity profiles and present a motion-filter model capable of predicting observers’ perceived amount of smear based on their eyes’ trajectories, suggesting a direct link between perceptual and saccade dynamics. Replays of the visual consequences of saccades during fixation led to virtually identical results as actively making saccades, whereas the additional simulation of perisaccadic contrast suppression heavily reduced this similarity, providing strong evidence that this suppression explained neither our findings nor the phenomenon of omission. Saccadic omission of motion smear may be understood as emerging naturally from the interplay of the retinal consequences of saccades and early visual processing.