Cite as:
Andrews T J, Glennerster A, Parker A J, 2000, "Stereoacuity thresholds are not symmetrical about the fixation plane in the presence of a reference surface" Perception 29 ECVP Abstract Supplement

Stereoacuity thresholds are not symmetrical about the fixation plane in the presence of a reference surface

T J Andrews, A Glennerster, A J Parker

With isolated stereo targets, the best depth discrimination is found in the fixation plane [eg Blakemore, 1970 Journal of Physiology (London) 211 599 - 622].

We measured stereoacuity thresholds in the presence and absence of a frontoparallel reference surface to determine whether the plane of maximal stereoacuity was altered by the reference surface. Subjects judged the depth of a vertical target line presented above a comparison line in a blank window within a random-dot field. Exposure duration was 150 ms and psychometric functions with different conditions were interleaved to reduce the likelihood of anticipatory vergence movements. Without a reference surface, thresholds rose as the target and comparison were moved away from the horopter. With a reference surface, stereo thresholds were (i) lowered by adding the surface at the same depth as the comparison line, and (ii) no longer symmetrical about the fixation plane. Thus, they were consistently lower for pedestal disparities with the same sign as the reference surface. The implication is that the reference surface has influenced the stereoscopic system at a level that is often assumed to be anatomically hard-wired.

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