Visual Encoding of Tilt from Optic Flow: Psychophysics and Computational Modelling

Abstract

Many computational models indicate ambiguities in the recovery of plane orientation from optic flow. Here we questioned whether psychophysical responses agree with these models. We measured the perceived tilt of a plane rotating in depth with two-view stimuli for 9 human observers. Response accuracy was higher under wide-field perspective projection (60°) than in small field (8°). Also, it decreased when the tilt and frontal translation were orthogonal rather than parallel. This effect was stronger in small field than in large field. Different computational models focusing on the recovery of plane orientation from optic flow can account for our results when associated with a hypothesis of minimal translation in depth. However, the twofold ambiguity predicted by these models is usually not found. Rather, most responses show a shift of the reported tilts toward the spurious solution with concomitant increase in response variability. Such findings point to the need for further simulations of the computational models.