Hyerim Kim¹, Oakyoon Cha¹; ¹Department of Psychology, Sogang University

Motion silencing is a visual illusion in which feature changes in small elements become less noticeable when they move together as a group. Previous studies on motion silencing typically presented task-relevant elements whose features changed, and participants reported those changes. The current study asked whether adding task-irrelevant, moving elements can strengthen the motion-silencing effect on the task-relevant elements. This question is partially motivated by Wu and colleagues (2024), who showed that motion embedded in the background can alter the strength of motion silencing. Participants viewed two arrays to the left and right of fixation. Each array contained small visual elements that moved either upward or downward at individually sampled speeds. The average motion speed was matched across the two arrays. On each trial, participants judged which array contained elements whose colors alternated between yellow and blue. In the other, comparison array, elements had static colors randomly sampled along the yellow–blue continuum. We indexed the strength of motion silencing by reaction time (RT), as longer RT indicates greater difficulty in detecting color changes. Thin horizontal bars were added to both arrays in two experimental conditions. In the Bars-In condition, the bars were attached to and moved in synchrony with the task-relevant target elements, whereas in the Bars-Out condition, the bars moved independently of the targets. In the No-Bars condition, the arrays contained no additional elements. The motion-silencing effect was stronger in both the Bars-Out and Bars-In conditions than in the No-Bars condition, with no difference between the Bars-Out and Bars-In conditions. These results suggest that additional motion signals within the display enhance the motion-silencing effect, regardless of whether they originate from the elements undergoing feature changes.

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