Humans use both form and motion information for heading perception

Abstract

It has long been known that humans use the focus of expansion (FOE) in a radial optic flow pattern to perceive their instantaneous direction of self-motion (heading). Here we report that motion-streak-like form information is also used for heading perception. We presented observers with an integrated form and motion display in which the dot pairs of a radial Glass patterns were oriented toward one direction on the screen (the form FOE) while moving in a different direction in depth (the motion FOE). Heading judgments were strongly biased towards the form FOE. We then manipulated the global form strength in the integrated display by randomly orienting certain dot pairs in the radial Glass pattern. As the global form strength in the radial Glass pattern decreased, so did the heading bias towards the form FOE. Lastly, we examined how the local effect of each dot-pair orientation on its perceived motion direction shifted heading estimation. We found that the visual system functioned like a maximum-likelihood integrator in combining the global and local interactions between form and motion signals for heading perception. The findings support the claim that humans make optimal use of both form and motion information for heading perception.