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Valentina Dilda, Sarah H. Creem-Regehr, William B. Thompson; Angle of elevation influences distance perception to targets on the ceiling. Journal of Vision 2006;6(6):420. doi: 10.1167/6.6.420.
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Consistent results show that distance perception to targets on the ground is indicated accurately by visually directed action tasks such as walking without vision. Recently, we (Dilda, Creem-Regehr, and Thompson, 2005) found similar accurate performance when targets were placed on the ceiling, a surprising result since the ground surface is likely an important source of information for distance. Base-up prisms lower the location of objects in the visual field and were used by Ooi, Wu and He (2001) to demonstrate that the visual system may use angular declination below the horizon to determine absolute distance to targets located on the ground. We asked whether a similar manipulation of angular declination/elevation off the horizon would influence absolute distance judgments to targets on the ceiling. We placed targets on the ceiling of a large room at distances of 5, 10, 15, and 20 feet. Participants were asked to walk without vision so that their bodies were aligned underneath the targets. They performed the task first with control goggles made of flat lenses and second with 10 Prism Diopter (5.73 degrees) base-up prism goggles. We replicated the results of accurate walking to targets on the ceiling with the flat lenses and found a consistent overestimation with the prism lenses relative to the control condition. The results suggest that the angle of elevation from the horizon to the ceiling informs the perception of distance to targets on the ceiling but leaves open the question of how accurate scaling is determined.
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