Visual guidance of locomotion.

THE USUAL CONCEPTION OF VISUAL GUIDANCE OF LOCOMOTION IS THAT IT INVOLVES THE PROBLEM OF KNOWING WHERE ONE IS HEADING. IT HAS BEEN SHOWN THAT THIS POINT CORRESPONDS TO THE CENTER OF THE RADIAL VISUAL EXPANSION OF THE SURFACE BEING APPROACHED; AND A NUMBER OF WAYS IN WHICH THE EXPANSION PATTERN MIGHT BE UTILIZED IN DETECTING THIS POINT HAVE BEEN SUGGESTED. THIS CONCEPTION OF THE PROBLEM IS REJECTED AND IT IS ARGUED THAT GUIDANCE SITUATIONS REQUIRING ACCURACY INVOLVE LOCOMOTION TOWARD A SPECIFIC TARGET. THE PERCEPTUAL INFORMATION FOR THIS GUIDANCE IS PROVIDED BY THE MOVEMENT OF THIS TARGET, THE PRESENCE AND NATURE OF ANY DRIFT SIGNALING THE PRESENCE OF A HEADING ERROR, AND THE NATURE OF THE CORRECTION REQUIRED. THE RESULTS FROM A NIGHT-DRIVING SIMULATOR CURRENTLY BEING USED AT THE UNIVERSITY OF THE NEW SOUTH WALES FIT THE DRIFT-CANCELLATION HYPOTHESIS AS THE POSITION OF THE TAILLIGHTS WAS STABILIZED AND DRIFT CANCELLED. /AUTHOR/