The detection of moving objects by moving observers

When an observer moves through the world, he or she must detect moving objects in order to avoid or intercept them. Accomplishing this task presents a problem for the visual system, because the motion of the observer causes the images of nearly all objects in the scene to move across the retina. We tested observers' abilities to detect a moving object when its angle of motion deviated from the radial optic flow pattern generated by observer motion in a straight line. To test whether global information is important for this task, we compared the results for a radial pattern with those for a deformation pattern. The results show that observer accuracy depends on the global pattern of the optic flow. In addition, we tested the effects of the duration of the trial, the number of objects, the eccentricity of the moving object and the speed of the observer.