Induction of Monocular Stereopsis by Altering Focus Distance: A Test of Ames's Hypothesis.

Dhanraj Vishwanath

doi:10.1177/2041669516643236

Dhanraj Vishwanath

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https://doi.org/10.1177/2041669516643236

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Journal: i-Perception	Publication Date: Mar 1, 2016
Citations: 5	License type: cc-by

Affiliation: University of St Andrews

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Viewing a real three-dimensional scene or a stereoscopic image with both eyes generates a vivid phenomenal impression of depth known as stereopsis. Numerous reports have highlighted the fact that an impression of stereopsis can be induced in the absence of binocular disparity. A method claimed by Ames (1925) involved altering accommodative (focus) distance while monocularly viewing a picture. This claim was tested on naïve observers using a method inspired by the observations of Gogel and Ogle on the equidistance tendency. Consistent with Ames’s claim, most observers reported that the focus manipulation induced an impression of stereopsis comparable to that obtained by monocular-aperture viewing.

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Viewing a real three-dimensional scene or a stereoscopic image with both eyes generates a vivid phenomenal impression of depth known as stereopsis
These findings suggest that the referent of the term ‘‘stereopsis’’ should be the perceptual effect itself rather than a specific condition that
Ames (1925) described several methods for inducing monocular stereopsis in single pictures, one of which involved ‘‘changing the accommodation of the eyes from that normally required by the distance from which the picture is viewed.’’ Ames suggested doing this by using concave or convex lenses, and there are suggestions that devices like the Zograscope (Koenderink, Wijntjes, & Kappers, 2013) which induce the impression of stereopsis rely on a similar idea (Wijntjes, in press)

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Viewing a real three-dimensional scene or a stereoscopic image with both eyes generates a vivid phenomenal impression of depth known as stereopsis. This claim has been empirically confirmed: Naive observers report the induction of the same qualitative visual attributes under monocular-aperture viewing of single pictures as under stereoscopic perception, including the impression of real negative space and separation, a sense of protrusion (‘‘things stick out towards me’’), and an impression of tangibility and realness to objects (Vishwanath & Hibbard, 2013).

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