Wiebke Nörenberg^1,2 (), Richard Schweitzer⁴, Martin Rolfs^1,2,3; ¹Humboldt-Universität zu Berlin, ²Berlin School of Mind and Brain, ³Cluster of Excellence ‘Science of Intelligence’, TU Berlin, ⁴Centro Interdipartimentale di Mente e Cervello, Università degli studi di Trento

Saccadic omission—the lack of conscious perception of visual information during saccadic eye movements—contributes to perceptual stability despite rapid retinal image shifts. Motion masking, the reduction of perceived motion amplitude through the presentation of static images before and after high-speed motion (Duyck et al., 2018), may support saccadic omission by reducing motion signals. Early visual motion processing relies on speed-sensitive neurons encoding its direction and speed, whereas amplitude perception likely involves both early and higher-order visual pathways. Speed and amplitude may thus be differentially affected by motion masking. We hypothesized that masking reduces both speed and amplitude perception and predicted that it impairs participants’ ability to accurately track the decrease in their perceptual performance, reflecting limited metacognitive access. Participants viewed a repetitive background pattern (constructed from 1/f pink noise) moving left or right, with motion varying in amplitude (6, 12, 18 dva), duration (39.2, 55.4, 71.6 ms), and velocity profile (constant vs. saccadic-like). The pattern was identical before and after motion, eliminating endpoint cues. Masking intervals — static presentations of the same background before and after motion — ranged from 0 to 320 ms. In two sessions, participants adjusted on-screen stimuli to report perceived amplitude (using an arrow) or speed (using brief stimulus presentations) respectively, and rated confidence in their judgments on a four-point scale. Both perceived motion amplitude and speed strongly decreased with increasing masking durations across all motion amplitudes. Saccade-like velocity profiles induced masking effects in the absence of explicit masking intervals, suggesting naturalistic motion kinematics contribute to masking in natural vision. Confidence ratings revealed a dissociation between perceptual accuracy and metacognitive access, as participants confidence ratings did not reflect the decline in performance. These results demonstrate that purely visual mechanisms robustly reduce amplitude and velocity perception of saccade-like motion signals, likely supporting perceptual stability during eye movements.

Acknowledgements: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. [865715 – VIS-A-VIS]).