Quan Lei¹ (), Evelyn Wilson¹; ¹Wichita State University

Previous research reported a sex difference in visual motion processing, with males generally having lower thresholds than females (Murray et al., 2018). Viewing random dot kinematograms (RDK), participants were found to show a tendency to perceive the opposite direction of global motion (Bae & Luck, 2022). The current study investigated if a sex difference exists in perceiving the opposite direction of global motion and if such difference depends on central vs. peripheral viewing. 14 female and 14 male participants made judgements about the global motion direction of RDK stimuli consisting of 120 dots moving in a 10° circular field (contrast: 60%, speed: 6°/s, lifetime: 50 ms, duration: 300 ms). There were four directions: left, right, up and down, and seven coherence levels varying between 5% and 95%. The stimuli were either viewed centrally at the fixation or peripherally at 10° eccentricity to the left or right of fixation. A sex difference of similar size was found in direction discrimination accuracy for both central and peripheral viewing, with males being more accurate than females (η2 =.198). Inspecting the confusion matrix, there was a strong tendency for participants of both sexes to report the opposite direction (compared with orthogonal directions) even at high coherence levels. However, the tendency was significantly stronger for females, such that if motion axis (instead of direction) was considered, there was no longer a sex difference in accuracy. Additionally, with peripheral viewing, females showed a pronounced tendency to perceive downward motion for stimuli moving along the vertical axis, no such asymmetry existing for males. These results indicate that the sex difference in direction judgement of global motion can be entirely explained by a differential process of disambiguating the two opposite directions along the same motion axis, presumably reflecting a sex difference in spatiotemporal filtering of motion signals.