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Anna Ma-Wyatt, Suzanne P. McKee, Preeti Verghese; Stereopsis is not useful in guiding simple pointing movements. Journal of Vision 2004;4(8):403. doi: 10.1167/4.8.403.
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© ARVO (1962-2015); The Authors (2016-present)
Goal directed actions like grasping or pointing are more accurate when vision is available, compared to cases in which vision is not available. However, what aspects of vision aid the guidance of action is yet not well understood. We used a simple localization task to investigate whether stereo information, known to aid in the judgments of relative distance in the z-dimension, contributed to precision for pointing. We asked subjects to make a ballistic point to a position on a screen under two sets of conditions. In the first, we presented brief bright dots at randomly selected locations on a touch screen that was either frontoparallel, or slanted away from the observer about the horizontal or vertical axis. In the second condition, we constructed a light but firm mask which contained either a single aperture or multiple apertures. The mask was placed approximately 3cm away from the surface of the monitor. Subjects had to guide their hand through the aperture in the mask to point to the position of a briefly presented dot. The aperture was large enough to access the positions of the dots. In all cases, the position of the dot was varied from trial to trial and feedback for speed and spatial accuracy was always given. Subjects completed the task with a binocular view, and with a monocular view (one eye covered by an eye patch) for both the dominant and non-dominant eyes. As expected, there was little difference between monocular and binocular conditions when subjects pointed to dots in the frontoparallel plane. When making a point to a target on a slanted surface, monocular viewing produced slightly greater spatial variability compared to pointing responses made at the same eccentricity in the frontoparallel plane with binocular viewing. With both masks, there was little difference between performance under binocular or monocular conditions. For these particular tasks, stereo information does not seem to be critical for the accurate guidance of hand movements.
R.C. Atkinson Fellowship (AMW); NEI Grant R01-EY06644 (SPM); NASA grant NAG9-1461 (PV)
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