Comparing masking and habituation roles in saccadic omission of stimuli optimized for intra-saccadic vision

Saccadic eye movements produce a rapid visual motion stimulation that remains unseen, a phenomenon known as saccadic omission. We have recently suggested that the sensorimotor system selectively habituates to, and thereby omits, the visual contingencies of saccades. In previous studies, a passive mechanism of saccadic omission was proposed in which the post-saccadic image serves as a backward mask to hide intra-saccadic motion from awareness. Here, we directly compared these theories using stimuli optimized for intra-saccadic vision: high-speed gratings that become visible only during the execution of saccades. In Experiment 1, we tested backward masking for three intra-saccadic motion stimuli (sudden-onset stationary grating, sudden-onset moving grating, and smooth-onset moving grating) by presenting a post-saccadic mask at saccade offset. Masking strongly reduced subjective motion report for sudden-onset stimuli but had little effect on smooth-onset motion, suggesting that gradual trans-saccadic transitions can bypass visual masking. In Experiment 2, repeated exposure reduced the detection of smooth-onset motion, but sudden-onset motion showed no reliable change. Thus, intra-saccadic habituation acts as an adaptive reduction in sensitivity to predictable motion associated with eye movements. Together, the results reveal complementary roles of masking and habituation in maintaining visual stability: Transient masking primarily impacts sudden intra-saccadic transients, whereas habituation tunes perception to predictable self-generated motion.