Sampling limits and critical bandwidth for letter discrimination in peripheral vision.

We develop and test two functional hypotheses based on the sampling theory of visual resolution that might account for letter acuity in peripheral vision. First, a letter smaller than the acuity limit provides insufficient veridical energy for performing the task, and, second, the available veridical energy is masked by increased amounts of visible but aliased energy. These two hypotheses make opposite predictions about the effect of low-pass filtering on letter acuity, which we tested experimentally by using filtered letters from the tumbling-E alphabet. Our results reject the masking hypothesis in favor of the energy insufficiency hypothesis. Additional experiments in which high-pass-filtered letters were used permitted the isolation of a critical band of spatial frequencies, which is necessary and sufficient for achieving maximum visual acuity. This critical band varied with the particular pair of letters to be discriminated but was in the range 0.9-2.2 cycles per letter.

[1]  J Rovamo,et al.  Resolution of gratings oriented along and across meridians in peripheral vision. , 1982, Investigative ophthalmology & visual science.

[2]  David Williams,et al.  No aliasing at edges in normal viewing , 1992, Vision Research.

[3]  G. Legge,et al.  Psychophysics of reading—I. Normal vision , 1985, Vision Research.

[4]  G. Sperling,et al.  Object spatial frequencies, retinal spatial frequencies, noise, and the efficiency of letter discrimination , 1991, Vision Research.

[5]  A. Bradley,et al.  Aliased Frequencies Enable the Discrimination of Compound Gratings in Peripheral Vision , 1997, Vision Research.

[6]  A. Bradley,et al.  Interaction between sub- and supra-Nyquist spatial frequencies in peripheral vision , 1997, Vision Research.

[7]  V. M. Bondarko,et al.  What spatial frequency do we use to detect the orientation of a Landolt C? , 1997, Vision Research.

[8]  David Williams.  Aliasing in human foveal vision , 1985, Vision Research.

[9]  L N Thibos,et al.  Relationship between acuity for gratings and for tumbling-E letters in peripheral vision. , 1999, Journal of the Optical Society of America. A, Optics, image science, and vision.

[10]  L. N. Thibos,et al.  Vision beyond the resolution limit: Aliasing in the periphery , 1987, Vision Research.

[11]  L N Thibos,et al.  Effect of window size on detection acuity and resolution acuity for sinusoidal gratings in central and peripheral vision. , 1996, Journal of the Optical Society of America. A, Optics, image science, and vision.

[12]  L A Temme,et al.  Peripheral Visual Field is Radially Organized , 1985, American journal of optometry and physiological optics.

[13]  D. Williams,et al.  Cone spacing and the visual resolution limit. , 1987, Journal of the Optical Society of America. A, Optics and image science.

[14]  David R. Williams,et al.  Off-axis optical quality and retinal sampling in the human eye , 1996, Vision Research.

[15]  Dennis M. Levi,et al.  The role of separation and eccentricity in encoding position , 1990, Vision Research.

[16]  L N Thibos,et al.  Psychophysical Localization of the Human Visual Streak , 1992, Optometry and vision science : official publication of the American Academy of Optometry.

[17]  Gordon E. Legge,et al.  Spatial-frequency dependence of eetter recognition in central and peripheral vision , 1997 .

[18]  A. Bradley,et al.  Characterization of spatial aliasing and contrast sensitivity in peripheral vision , 1996, Vision Research.

[19]  Larry N. Thibos,et al.  Undersampling produces non-veridical motion perception, but not necessarily motion reversal, in peripheral vision , 1996, Vision Research.

[20]  Robert F. Hess,et al.  Is the increased spatial uncertainty in the normal periphery due to spatial undersampling or uncalibrated disarray? , 1993, Vision Research.

[21]  M. Banks,et al.  Sensitivity loss in odd-symmetric mechanisms and phase anomalies in peripheral vision , 1987, Nature.

[22]  L N Thibos.  Acuity perimetry and the sampling theory of visual resolution. , 1998, Optometry and vision science : official publication of the American Academy of Optometry.

[23]  Denis G. Pelli,et al.  The visual filter mediating letter identification , 1994, Nature.

[24]  K. Alexander,et al.  Spatial-frequency characteristics of letter identification. , 1994, Journal of the Optical Society of America. A, Optics, image science, and vision.