Abstract
There is considerable support for the hypothesis that heading perception is mediated by instantaneous optic flow. This hypothesis, however, has never been tested. We introduce a novel method, termed “phase motion,” for generating a stimulus that conveys a single instantaneous optic flow field, even though the stimulus is presented for an extended period of time. In this experiment, observers viewed stimulus videos and performed a forced choice heading discrimination task. For phase motion stimuli, observers made large errors in their judgments of heading direction. This suggests that instantaneous optic flow is insufficient for heading perception. These errors were mostly eliminated when the velocity of phase motion was varied over time to convey an evolving sequence of flow fields. This demonstrates that heading perception relies on the time-varying evolution of optic flow.
Footnotes
↵* e-mail: charlie.burlingham{at}nyu.edu;david.heeger{at}nyu.edu