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Vertical gaze angle: absolute height-in-scene information for the programming of prehension

Gardner, P.L. and Mon-Williams, M. (2001) Vertical gaze angle: absolute height-in-scene information for the programming of prehension. Experimental Brain Research, 136 (3). pp. 379-385. ISSN 0014-4819

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Abstract

One possible source of information regarding the distance of a fixated target is provided by the height of the object within the visual scene. It is accepted that this cue can provide ordinal information, but generally it has been assumed that the nervous system cannot extract "absolute" information from height-in-scene. In order to use height-in-scene, the nervous system would need to be sensitive to ocular position with respect to the head and to head orientation with respect to the shoulders (i.e. vertical gaze angle or VGA). We used a perturbation technique to establish whether the nervous system uses vertical gaze angle as a distance cue. Vertical gaze angle was perturbed using ophthalmic prisms with the base oriented either up or down. In experiment 1, participants were required to carry out an open-loop pointing task whilst wearing: (1) no prisms; (2) a base-up prism; or (3) a base-down prism. In experiment 2, the participants reached to grasp an object under closed-loop viewing conditions whilst wearing: (1) no prisms; (2) a base-up prism; or (3) a base-down prism. Experiment 1 and 2 provided clear evidence that the human nervous system uses vertical gaze angle as a distance cue. It was found that the weighting attached to VGA decreased with increasing target distance. The weighting attached to VGA was also affected by the discrepancy between the height of the target, as specified by all other distance cues, and the height indicated by the initial estimate of the position of the supporting surface. We conclude by considering the use of height-in-scene information in the perception of surface slant and highlight some of the complexities that must be involved in the computation of environmental layout.

Item Type: Article
Keywords: prehension; distance perception; motor programming; visual cues; height-in-scene; human
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Medicine and Health (Leeds) > Institute of Psychological Sciences (Leeds) > Cognitive Psychology (Leeds)
Depositing User: Repository Officer
Date Deposited: 19 Jun 2009 11:05
Last Modified: 29 Sep 2010 14:24
Published Version: http://dx.doi.org/10.1007/s002210000590
Status: Published
Publisher: Springer Verlag
Identification Number: 10.1007/s002210000590
URI: http://eprints.whiterose.ac.uk/id/eprint/8682

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