Object correspondence across movements at saccadic speed

Saccadic eye movements impose rapid motion on the retinal image, raising the question of how object correspondence is established from one fixation to the next. Here, we investigated if the rapid motion itself — by providing spatiotemporal continuity — plays a role in achieving object correspondence. To isolate the contribution of high-speed motion, we simulated saccadic motion using a high-temporal-resolution projector (updating the display every 0.69 ms) while observers fixated their gaze throughout the experiments. We first investigated the contribution of motion at saccadic speed to object correspondence using a two-frame quartet-motion display. We positioned identical Gabor patches as objects at opposing corners within an imaginary rectangle. One object then moved continuously — along a curved trajectory (inward or outward) — to one of the neighboring corners, while the other jumped to the opposite side, completing the quartet. On each trial, participants first reported quartet rotations (clockwise or counterclockwise), indicating perceived object correspondence, and then traced the perceived continuous motion trajectory using a mouse, indicating motion visibility (location and curvature). We found that motion visibility declined as speed increased, eventually reaching chance levels for location and curvature reports. At the same time, continuous motion biased the quartet rotation perception even at the highest (saccade-like) speeds. These results suggest that high-speed motion informs object correspondence, even if that motion is effectively invisible. We are currently following up on this finding in a second study, in which we combine a version of our quartet motion display with the go/no-go reviewing paradigm (Sasi et al., 2023). We investigate if object files are maintained through motion at saccadic speed. By combining objective measures of stimulus visibility, the perception of object correspondence, and the maintenance of object files over time, we aim to shed light on the fundamental mechanisms behind object continuity at saccadic speeds.