Hyerim Kim¹, Oakyoon Cha¹; ¹Sungshin Women's University

Motion silencing refers to a visual illusion in which changes in visual features of small dots, such as color or luminance, become less noticeable when the dots move coherently as a group. Previous studies have typically presented dots changing color or luminance against a uniform gray background, which may have inadvertently caused switches in contrast polarity throughout the sequence, potentially disrupting the ability of simple cells in the primary visual cortex (V1) to continuously track these changes. Since simple cells are more sensitive to luminance contrast than complex cells, we investigated whether enhancing feature changes to align better with simple cells’ sensitivity could increase the visibility of the changes, thereby weakening the motion silencing illusion. Participants viewed two groups of 200 dots each in the left and right visual fields. In the comparison field, the dots did not move, while in the distractor field, the dots moved upward or downward at random speeds. All dots cycled in color between bright yellow and dark blue. The rate of color change was fixed at 1 Hz in the distractor field, whereas it was adjusted in the comparison field using a 1-up, 1-down adaptive staircase procedure. This procedure allowed us to estimate the point of subjective equality for each background condition (white, mid-level gray, and black), tested in separate blocks. The dots’ contrast was, on average, the least salient against the mid-level gray background, because its luminance was between that of bright yellow and dark blue. In addition, the gray background likely disrupted V1 simple cells’ ability to track dots’ luminance changes, resulting in stronger motion silencing. Nonetheless, Bayesian ANOVA revealed no differences across background conditions. These findings suggest that motion silencing illusion persists across varying background conditions, highlighting its robustness even when differences in luminance contrast are introduced.

Acknowledgements: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Science and ICT) (No. RS-2023-00211668).