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G. L. McCormack, C. Meyer, L. Deng, S. Han; Manual versus Perceptual Estimates of Vergence-Induced Motion-in-Depth. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1826.
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McCormack et al. (Journal of Vision. 2007; 7(9): VSS abstract #72) observed that vergence-induced motion-in-depth, measured by matching an unseen hand to target distance, decayed as vergence oscillation rate dropped below 0.12Hz. They speculated that the vergence depth cue may be specialized for vision-for-action. In this study we tested whether recalled depth perception was also impacted by vergence rate, and if so, whether the rate effects were equal in recalled and manual responses.
In dark surrounds subjects viewed, through pinhole apertures, a haploscopically-generated vertical line oscillating in depth between 14Δ and 22Δ at rates from 0.03Hz to 0.5 Hz. In separate counterbalanced sessions subjects manually matched an unseen moveable peg to target distance, or recalled the apparent limits of motion-in-depth after each trial. Motion-in-depth rate was randomized within sessions. Vergence was verified by infrared oculography.
Separate ANCOVAs with factors of log frequency and session order evaluated the two responses. Manual and memory responses both increased significantly with log frequency (p<0.0001 for both). Session order had no significant effect on either response (manual: p=0.95; memory: p=0.24). To determine whether the frequency-related gain had the same temporal behavior in the two responses, we regressed subjects' responses on log frequency and extrapolated the regressions to the zero amplitude frequency (the "cut-off frequency"). We compared these cut-off frequencies with a paired t-test. The mean cut-off frequencies of 0.0082Hz (memory) and 0.012Hz (manual) were not significantly different (p=0.247).
Perception receives the same dynamic depth information from vergence as does hand control when vergence is the sole depth cue.
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