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Charles R. Fox; Gaze Level: Oculomotor input to perceived distance. Journal of Vision 2002;2(7):524. doi: 10.1167/2.7.524.
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© ARVO (1962-2015); The Authors (2016-present)
There is growing evidence that gaze angle may be used as a distance cue. The precise role of gaze angle is unclear but one hypothesis suggests that oculomotor information about vertical gaze position is evaluated for distance perception. Previous experiments used targets significantly below eye level and used prism to alter gaze demand characteristics. Having the target always below anatomical eye level allow only relative evaluation of the effects of upward gaze. In addition, while the prisms result in relative upward gaze, the optical relation of gaze to ground plain is not affected. A further issue is that during ‘blind walking’ (a task commonly used), visually perceived eye level (VPEL) most likely changes. This may influence distance judgments.
The current experiment measures distance judgment by ‘blind walking’ to a visual target 15 meters away. The target was adjustable to either VPEL or anatomic eye level and 5 degrees above and below the respective eye level.
Results indicate a main, linear effect (ANOVA) of gaze level with people estimating distances as greater with up gaze and less with down gaze. This effect was primarily due to the conditions in which the target array was centered at anatomic eye level (above>anatomic eye level> below; above=VPEL=below) suggesting that VPEL does play a role in distance perception under these conditions. These results support the hypothesis that oculomotor information, presumably from the obliques, provides information for distance perception.
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