Abstract
Keeping track of moving objects is a core task of the visual system, as they change locations or disappear behind occluders. Most frequently, however, objects change places on the retina because the eyes move. Recent evidence suggests that an object’s continuous motion can become indiscriminable from apparent motion (a simple jump) when it follows the tight distance-duration relation with which objects shift across the retina during saccades (Rolfs et al., 2021). Capitalizing on this finding, we investigated if object motion obeying these saccade kinematics informs assignments of object correspondence across space and time. Participants reported the perceived motion direction in two-frame quartet motion displays: Two identical objects (vertical or horizontal Gabors) were displayed in opposite corners of a virtual rectangle (frame 1). After a brief blank period, they reappeared in the two remaining corners (frame 2), completing the quartet before disappearing again. Perceived direction of motion in this display provides direct access to perceived object correspondence (which object moved in which direction). Varying the aspect ratio of the quartet’s side lengths strongly shifted motion perception in either horizontal or vertical direction, favoring the shorter path between objects (the well-known proximity effect). Crucially, in half of the trials, we rapidly and continuously moved one of the objects (during the blank period) along either the horizontal or vertical path, following the distance-duration relation of saccades. Motion of the object parallel to its orientation was perceived as continuous motion, providing a control condition that eliminated the proximity effect. Motion of the object orthogonal to its orientation was perceived as apparent motion, but still biased the direction seen in the display, adding to or reducing the proximity effect when motion occurred along the shorter or longer path, respectively. Motion at saccadic speeds thus informs how the visual system routinely assigns object correspondence.