Roselind Si¹ (), Oliver Layton¹; ¹Colby College

Self-motion relative to a stationary environment generates a pattern of motion on the eye known as optic flow. Straight self-motion without eye movements or other sources of rotation creates an optic flow pattern where the motion radiates with respect to a singularity point that specifies the direction of travel (heading). Decades of research have characterized the accuracy with which humans are capable of perceiving heading from optic flow. In the typical experiment, subjects judge their heading after viewing optic flow simulating self-motion along a constant direction. A key assumption is that the heading judgment reflects human perception of the optic flow during the current trial. Recent work, however, has shown that the heading on previous trials (Sun, Zhang, Alais, & Li, 2020) and changes in heading hundreds of milliseconds before the judgment period (Ali, Decker, & Layton, 2023) influence the heading judgment. In the present work, we investigate how the ability to anticipate the heading in the current trial based on the preceding trials on heading judgments. We used a modified version of the paradigm of Ali et al. (2023) wherein subjects viewed straight-forward self-motion and the heading would switch leftward or rightward during the trial. When the direction of the heading switch predictably alternated sides across successive trials, human heading judgments exhibited bias toward the side of the heading switch on the preceding trial. We found no such bias when the side of the heading switch was randomized. When we created an imbalance in the switch directions (e.g. left switches more likely than right switches), judgments exhibited bias toward the side with fewer heading switches. Our findings suggest that expectations about heading based on the predictability and distribution of recently experienced headings may influence human heading perception.