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Julie M. Harris, Vit F. Drga; Scene layout and binocular distance perception: Effects of angular separation. Journal of Vision 2005;5(8):251. doi: 10.1167/5.8.251.
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© ARVO (1962-2015); The Authors (2016-present)
The ability to judge distance is critical for interacting with objects in our environment. In impoverished environments, distance perception can be radically altered by the pattern of relative binocular disparities between objects in the scene. For example, when two points are presented simultaneously, the farther point can appear at a constant distance, and the near point as nearer than when it is alone (far anchor effect). Effects like this have been modelled in terms of the visual system estimating a ‘reference distance’ and the distances of all other points being calculated using that distance and the disparity between the point and the reference. The reference distance is thought to be a weighted combination of the distances of scene points. Here we explore how the reference distance varies with the angular separation between points in a scene.
Observers viewed a simple scene containing two points presented in depth. In one condition, distance to the nearer point was varied (between around 12cm and 40cm) whilst the relative disparity between points was held constant (2.25 deg). In another, one point was held at a fixed distance (25cm) whilst the other's distance was varied. We compared distance estimates using both verbal and manual (pointing) responses for different angular vertical separations.
Our observers provided a wide range of responses, some exhibiting the far anchor effect, some producing a linear relationship between verbal and manual responses. For most observers and conditions, performance was similar across vertical separations. Some observers saw distances as slightly further away when points were more separated. This suggests that the reference point weighting does not differ dramatically across a range of angular separations.
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