Abstract
Research on time to contact has demonstrated that observers use tau information for the perception of collision events. Tau is an optical variable specified by the inverse rate of expansion of an approaching object and is independent of the speed of the observer and/or object. In the present study we examined whether other factors influence the detection of collisions. Observers were presented with displays simulating observer motion through a scene. Within the scene objects were present that translated independent of the observers motion. On each trial observers were presented with a varied number of objects in the scene and were asked to indicate whether or not an object was on a collision path with the observer. To determine whether other factors such as observer speed are important we systematically varied the speed of object and observer motion when TTC (time to contact) was constant. In addition, two different types of collisions were examined under constant TTC—Observer and object motion in opposite directions and observer and object motion in the same direction. If observers use TTC then variations in observer/object speed should not influence performance. The results indicated significant variations in collision detection as a function of different combinations of object and observer motion when TTC was constant. Collision detection increased with an increase in the number of objects in the scene. These results demonstrate that TTC is not the sole source of information for the detection of collisions and that the detection of collision events is influenced by speed information in the surrounding scene.
Supported by NIH Grant 1R01EY12437.