Cite as:
Rogers B J, Allison R S, 1999, "When do we use optic flow and when do we use perceived direction to control locomotion?" Perception 28 ECVP Abstract Supplement

When do we use optic flow and when do we use perceived direction to control locomotion?

B J Rogers, R S Allison

Optic-flow-field analyses have revealed that there are several sources of information to indicate the point of impact in a visual scene for a moving observer. Visual information alone, however, cannot indicate the heading direction, since heading is defined with respect to the observer. The importance of the distinction between the point of impact and the heading direction was brought out by Rushton et al [1998 Investigative Ophthalmology & Visual Science 39(4) S191] who showed that walking paths are determined primarily by the perceived direction of the target point. In contrast, many studies have shown that the point of impact can be detected with considerable precision by using a variety of different flow-field characteristics, so why doesn't optic flow play a more important role in controlling locomotion? Our results suggest that several factors are important. Locomotor paths are straighter when (i) there is local motion parallax between the intended target and objects at different distances; (ii) there is ground-plane texture and/or path markings; (iii) attention is directed towards the optic-flow cues. In addition, the extent to which we use flow-field information depends on the type of locomotion and the way in which heading direction is controlled by the observer.

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