Human heading judgments and object-based motion information.

In four experiments, we explored observers' ability to make heading judgments from simulated linear and circular translations through sparse forests and with pursuit fixation on one tree. We assessed observers' performance and information use in both regression and factorial designs. In all experiments we found that observers used three sources of object-based information to make their judgments--the displacement direction of the nearest object seen (a heuristic), inward displacement towards the fovea (an invariant) and outward deceleration (a second invariant). We found no support for the idea that observers use motion information pooled over regions of the visual field.