OPTICAL-FLOW NOT RETINAL FLOW IS THE BASIS OF WAYFINDING BY FOOT

Two experiments were directed at the hypothesis that wayfinding is ach ieved by a recursive strategy using differential motion parallax (DMP) , a property of retinal flow due to near and far objects moving agains t fixation. Experiment 1 showed that without the changing global optic al pattern due to translation of the eye, DMP failed to support wayfin ding accuracy in the 2 degrees-4 degrees range assumed necessary for g uiding locomotion. Experiment 2 revealed that the requisite accuracy w as achievable when displays simulating locomotion violated the conditi ons for the DMP strategy but included the optical flow pattern due to translation. It was concluded that DMP is neither necessary nor suffic ient for wayfinding; the information for wayfinding is in optical flow .