PERCEIVING HEADING IN THE PRESENCE OF MOVING-OBJECTS

In most models of heading from optic flow a rigid environment is assum ed, yet humans often navigate in the presence of independently moving objects. Simple spatial pooling of the flow field would yield systemat ic heading errors. Alternatively, moving objects could be segmented on the basis of relative motion, dynamic occlusion, or inconsistency wit h the global flow, and heading determined from the background flow. Di splays simulated observer translation toward a frontal random-dot plan e, with a 10 deg square moving independently in depth. The path of mot ion of the object was varied to create a secondary focus of expansion (FOE') 6 deg to the right or left of the actual heading point (FOE), w hich could bias the perceived heading. There was no effect when the FO E was visible, but when the object moved in front of it, perceived hea ding was biased toward the FOE' by similar to 1.9 degrees with a trans parent object, and similar to 3.4 degrees with an opaque object. The r esults indicate that scene segmentation does not occur prior to headin g estimation, which is consistent with spatial pooling weighted near t he FOE. A simple template model based on large-field, center-weighted expansion units accounts for the data. This may actually represent an adaptive solution for navigation with respect to obstacles on the path ahead.