Panum’s fusional area estimated with a criterion-free technique

It has been reported that criterion-free estimates of the upper disparity limits for fusion of line targets are small enough to be accounted for by monocular vernier sensitivity. However, targets such as lines, which contain high spatial frequencies, may ensure small fusion limits, since fusion limits obtained with criterion-dependent methods for narrow-band targets, such as sinusoids or difference-of-Gaussian luminance profiles, are proportional to target spatial periods. Experiment 1 therefore explored whether criterion-free methods give fusion limits for narrow-band targets that can be accounted for by vernier sensitivity. Vertical fusion limits were estimated by a method that forced observers to discriminate a disparate sinusoidal grating from an immediately adjacent zero-disparity grating. Fusion limits were too large to be explained by monocular vernier thresholds obtained for the same targets. In addition, fusion limits were not affected by large changes in target contrast, whereas vernier thresholds increased as contrast was decreased. The results of Experiment 1 also argued against interocular suppression as the cause of single vision, since vernier offsets that were visible when viewed monocularly were invisible under binocular viewing conditions. In Experiment 2, manual adjustment of disparities yielded fusion limits little different from those obtained with the forced-choice method of Experiment 1, demonstrating that it is possible to design adjustment methods for assessing fusion limits that are as sensitive as forced-choice methods. In Experiment 3, large reductions in target contrast, which have the effect of decreasing disparity sensitivity, did not alter fusion limits, disconfirming the idea that fusion limits estimated with discriminative procedures represent disparity-detection thresholds. In Experiment 4, disparities were adjusted until a just noticeable difference in grating contrast appeared. These disparities were larger than fusion limits, indicating that fusion limits did not represent a change in apparent contrast arising from disparity limitations of binocular summation. Together, the four experiments support the existence of binocular fusion as a unique category of sensory performance, disconfirm several nonfusional explanations of single vision, and support the use of criterion-free as well as adjustment methods in measuring fusion limits.

[1]  G. Brink,et al.  What is the diplopia threshold? , 1981, Perception & psychophysics.

[2]  R Blake,et al.  Disparity range for binocular summation. , 1988, Investigative ophthalmology & visual science.

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

[4]  H. Levitt.  Transformed up-down methods in psychoacoustics. , 1971, The Journal of the Acoustical Society of America.

[5]  R. A. Smith,et al.  Disparity processing of spatial frequencies in man , 1972, The Journal of physiology.

[6]  Aries Arditi,et al.  Singleness of vision and the initial appearance of binocular disparity , 1978, Vision Research.

[7]  Gordon E. Legge,et al.  Stereopsis and contrast , 1989, Vision Research.

[8]  L. Kaufman,et al.  Handbook of perception and human performance , 1986 .

[9]  C. Blakemore,et al.  Evidence for disparity detecting neurones in the human visual system , 1972, The Journal of physiology.

[10]  D. Ferster.  A comparison of binocular depth mechanisms in areas 17 and 18 of the cat visual cortex , 1981, The Journal of physiology.

[11]  Ian P. Howard,et al.  Human visual orientation , 1982 .

[12]  C. Tyler.  Spatial organization of binocular disparity sensitivity , 1975, Vision Research.

[13]  G. Brink,et al.  The effect of presentation time on detection and diplopia thresholds for vertical disparities , 1982, Vision Research.

[14]  C. Schor,et al.  Binocular sensory fusion is limited by spatial resolution , 1984, Vision Research.

[15]  P. Panum.  Physiologische Untersuchungen über das Sehen mit zwei Augen , 1858 .

[16]  B. Skottun,et al.  Effects of contrast and spatial frequency on vernier acuity , 1987, Vision Research.

[17]  R. Nussenblatt,et al.  Dynamics of experimental autoimmune uveoretinitis induced by adoptive transfer of S-antigen-specific T cell line. , 1988, Investigative ophthalmology & visual science.

[18]  B. Julesz,et al.  Extension of Panum's fusional area in binocularly stabilized vision. , 1967, Journal of the Optical Society of America.

[19]  Aries Arditi,et al.  The fusion illusion , 1976, Vision Research.

[20]  Clifton M. Schor,et al.  Is edge information for stereoacuity spatially channeled? , 1989, Vision Research.

[21]  M. De.  A review of the concept of "Panum's fusional areas". , 1966 .

[22]  James E. Sheedy,et al.  The perceived direction of the binocular image , 1979, Vision Research.

[23]  C. H. Graham,et al.  Vision and visual perception , 1965 .

[24]  A. Kertesz,et al.  The effect of stimulus complexity on human cyclofusional response. , 1972, Vision research.

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

[26]  Christopher W. Tyler,et al.  Spatio-temporal properties of Panum's fusional area , 1981, Vision Research.

[27]  Clifton Schor,et al.  Interocular differences in contrast and spatial frequency: Effects on stereopsis and fusion , 1989, Vision Research.

[28]  Christopher W. Tyler,et al.  Binocular fusion limits are independent of contrast, luminance gradient and component phases , 1989, Vision Research.

[29]  H. Ono,et al.  The cyclopean eye vs. the sighting-dominant eye as the center of visual direction , 1982, Perception & psychophysics.