Effects of spatial separation and retinal eccentricity on two-dot vernier acuity

Experiments investigated how vernier acuity for dot targets is affected by dot spatial separation and retinal eccentricity. Beck and Schwartz [Vision Res. 19, 313-319, 1979] found that the vernier thresholds increased linearly with interdot separation from 7.5 to 30 min arc. Experiment 1 showed that the vernier thresholds increased linearly with interdot separation from 0.5 to 8 deg arc. Experiments 2 and 3 showed that moving the dots into the periphery while keeping the interdot separation constant increased the threshold little if at all. The results are interpreted as supporting the hypothesis that there is (1) an encoding of dot positions in retinal coordinates, and (2) that the relative positions of the dots are made explicit in terms of the slope of the virtual line joining them. The increase in threshold with dot separation indicates that the visual system is unable to directly access and compare the retinal positions of the dots. The constancy of the threshold with eccentricity indicates that the visual system encodes the retinal positions of two well-separated dots as accurately in the periphery as in the fovea.

[1]  D. Hubel,et al.  Receptive fields, binocular interaction and functional architecture in the cat's visual cortex , 1962, The Journal of physiology.

[2]  S. McKee,et al.  Visual acuity in the presence of retinal-image motion. , 1975, Journal of the Optical Society of America.

[3]  L. Matin.  Eye Movements and Perceived Visual Direction , 1972 .

[4]  R. J. Watt,et al.  The use of different cues in vernier acuity , 1983, Vision Research.

[5]  F. W. Weymouth.  Visual sensory units and the minimal angle of resolution. , 1958, American journal of ophthalmology.

[6]  Yves le Grand,et al.  Form and Space Vision , 1967 .

[7]  H W Leibowitz,et al.  Independence of radial localization from refractive error. , 1980, Journal of the Optical Society of America.

[8]  D. P. Andrews,et al.  Acuities for spatial arrangement in line figures: human and ideal observers compared. , 1973, Vision research.

[9]  R. J. Watt,et al.  Mechanisms responsible for the assessment of visual location: Theory and evidence , 1983, Vision Research.

[10]  E. Ludvigh.  Direction sense of the eye. , 1953, American journal of ophthalmology.

[11]  S. McKee,et al.  Spatial configurations for visual hyperacuity , 1977, Vision Research.

[12]  G Stigmar,et al.  BLURRED VISUAL STIMULI , 1971 .

[13]  J. Beck,et al.  Vernier acuity with dot test objects , 1979, Vision Research.

[14]  S. McKee,et al.  Exposure duration affects the sensitivity of vernier acuity to target motion , 1983, Vision Research.

[15]  R. Watt,et al.  The recognition and representation of edge blur: Evidence for spatial primitives in human vision , 1983, Vision Research.

[16]  Suzanne P. McKee,et al.  Integration regions for visual hyperacuity , 1977, Vision Research.