OSA's Digital Library

Journal of the Optical Society of America A

Journal of the Optical Society of America A


  • Vol. 20, Iss. 7 — Jul. 1, 2003
  • pp: 1356–1370

Saccadic and perceptual performance in visual search tasks. II. Letter discrimination

Richard F. Murray, Brent R. Beutter, Miguel P. Eckstein, and Leland S. Stone  »View Author Affiliations

JOSA A, Vol. 20, Issue 7, pp. 1356-1370 (2003)

View Full Text Article

Acrobat PDF (722 KB)

Browse Journals / Lookup Meetings

Browse by Journal and Year


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools



Can the oculomotor system use shape cues to guide search saccades? Observers searched for target letters (D, U, or X) among distractors (the letter O in the discrimination task and blank locations in the detection task) in Gaussian white noise. We measured the accuracy of first saccadic responses on each trial and perceptual (i.e., button-press) responses in separate trials with the stimulus duration chosen so that the saccadic and perceptual processing times were matched. We calculated the relative efficiency of saccadic decisions compared with perceptual decisions, ηrel=(dsac/dper)2. Relative efficiency was low but consistently greater than zero in discrimination tasks (15%±6%) and high in detection tasks (60%±10%). We conclude that the saccadic targeting system can use shape cues, but less efficiently than the perceptual system can.

© 2003 Optical Society of America

OCIS Codes
(330.2210) Vision, color, and visual optics : Vision - eye movements
(330.4060) Vision, color, and visual optics : Vision modeling
(330.5000) Vision, color, and visual optics : Vision - patterns and recognition
(330.5510) Vision, color, and visual optics : Psychophysics
(330.6100) Vision, color, and visual optics : Spatial discrimination
(330.7310) Vision, color, and visual optics : Vision

Richard F. Murray, Brent R. Beutter, Miguel P. Eckstein, and Leland S. Stone, "Saccadic and perceptual performance in visual search tasks. II. Letter discrimination," J. Opt. Soc. Am. A 20, 1356-1370 (2003)

Sort:  Author  |  Year  |  Journal  |  Reset


  1. J. M. Findlay, “Saccade target selection during visual search,” Vision Res. 37, 617–631 (1997).
  2. I. T. Hooge and C. J. Erkelens, “Peripheral vision and oculomotor control during visual search,” Vision Res. 39, 1567–1575 (1999).
  3. P. Viviani and R. G. Swensson, “Saccadic eye movements to peripherally discriminated visual targets,” J. Exp. Psychol. Hum. Percept. Perform. 8, 113–126 (1982).
  4. P. Y. He and E. Kowler, “The role of location probability in the programming of saccades: implications for ‘center-of-gravity’ tendencies,” Vision Res. 29, 1165–1181 (1989).
  5. L. G. Williams, “The effects of target specification on objects fixated during visual search,” Acta Psychol. 27, 355–360 (1967).
  6. G. J. Zelinsky, “Using eye saccades to assess the selectivity of search movements,” Vision Res. 36, 2177–2187 (1996).
  7. M. P. Eckstein, B. R. Beutter, and L. S. Stone, “Quantifying the performance limits of human saccadic targeting during visual search,” Perception 30, 1389–1401 (2001).
  8. B. R. Beutter, M. P. Eckstein, and L. S. Stone, “Saccadic and perceptual performance in visual search tasks. I. Contrast detection and discrimination,” J. Opt. Soc. Am. A 20, 1341–1355 (2003).
  9. D. M. Green and J. A. Swets, Signal Detection Theory and Psychophysics (Krieger, Huntington, N.Y., 1974).
  10. W. S. Geisler, “Sequential ideal-observer analysis of visual discriminations,” Psychol. Rev. 96, 267–314 (1989).
  11. H. Kukkonen, J. Rovamo, K. Tiippana, and R. Nasanen, “Michelson contrast, RMS contrast and energy of various spatial stimuli at threshold,” Vision Res. 33, 1431–1436 (1993).
  12. P. Whittle, “Increments and decrements: luminance discrimination,” Vision Res. 26, 1677–1691 (1986).
  13. D. J. Tolhurst and Y. Tadmor, “Band-limited contrast in natural images explains the detectability of changes in the amplitude spectra,” Vision Res. 37, 3203–3215 (1997).
  14. B. R. Beutter and L. S. Stone, “Human motion perception and smooth eye movements show similar directional biases for elongated apertures,” Vision Res. 38, 1273–1286 (1998).
  15. W. Becker and R. Jurgens, “An analysis of the saccadic system by means of double step stimuli,” Vision Res. 19, 967–983 (1979).
  16. Oculomotor error in directing saccades almost certainly had little effect on saccadic accuracy, because there was a 360 deg ÷10=36 deg range corresponding to each stimulus location. Using identical methods, Beutter et el.8 recorded saccadic responses approaching 100% correct.
  17. W. W. Peterson, T. G. Birdsall, and W. C. Fox, “The theory of signal detectability,” IRE Trans. Inf. Theory 4, 171–212 (1954).
  18. In an M-alternative localization task, the ideal observer’s strategy is to cross-correlate the stimulus at each of the M possible target locations with a template that is the difference image between the target and the distractor and to choose the location with the largest cross correlation. See Ref. 8 for details.
  19. See Ref. 9, Appendix 1, for a description of how to calculate d in an M-alternative forced-choice task.
  20. J. A. Solomon and D. G. Pelli, “The visual filter mediating letter identification,” Nature (London) 369, 395–397 (1994).
  21. J. R. Taylor, An Introduction to Error Analysis: The Study of Uncertainties in Physical Measurements (University Science, Mill Valley, Calif., 1982).
  22. M. P. Eckstein, A. J. Ahumada, Jr., and A. B. Watson, “Visual signal detection in structured backgrounds. II. Effects of contrast gain control, background variations, and white noise,” J. Opt. Soc. Am. A 14, 2406–2419 (1997).
  23. B. Efron and R. Tibshirani, An Introduction to the Bootstrap (Chapman & Hall, New York, 1993).
  24. For all observers, the uncertainty parameters of the pooled oculometric and psychometric functions were significantly greater than zero (p<0.01). Beutter et el.8 found that in disk contrast discrimination tasks, uncertainty was near zero for both saccadic and perceptual responses. This difference is probably due to the fact that Beutter et el.’s discrimination task had a contrast pedestal, whereas ours did not. That is, at low SNRs in our task, target and distractor letters were shown at contrasts that were near their detec-tion threshold. Low-contrast viewing conditions tend to increase uncertainty (see Ref. 22).
  25. D. G. Pelli, C. W. Burns, B. Farrell, and D. C. Moore, “Identifying letters,” Vision Res. (in press).
  26. A. B. Watson, “Visual detection of spatial contrast patterns: evaluation of five simple models,” Opt. Express 6, 12–33 (2000).
  27. M. P. Eckstein and S. S. Shimozaki, “Classification images for saccadic targeting and perceptual decisions during search,” Perception 32 (supplement), 10 (2002).
  28. R. H. Wurtz and J. E. Albano, “Visual-motor function of the primate superior colliculus,” Annu. Rev. Neurosci. 3, 189–226 (1980).
  29. A. F. Fuchs, C. R. Kaneko, and C. A. Scudder, “Brainstem control of saccadic eye movements,” Annu. Rev. Neurosci. 8, 307–337 (1985).
  30. D. L. Sparks, “The brainstem control of saccadic eye movements,” Nature Rev. Neurosci. 3, 952–964 (2002).
  31. P. H. Schiller and E. J. Tehovnik, “Look and see: how the brain moves your eyes about,” Prog. Brain Res. 134, 127–142 (2001).
  32. J. D. Schall, “The neural selection and control of saccades by the frontal eye field,” Philos. Trans. R. Soc. London Ser. B 357, 1073–1082 (2002).
  33. W. Fries, “Cortical projections to the superior colliculus in the macaque monkey: a retrograde study using horseradish peroxidase,” J. Comp. Neurol. 230, 55–76 (1984).
  34. R. J. Krauzlis and L. S. Stone, “Tracking with the mind’s eye,” Trends Neurosci. 22, 544–550 (1999).
  35. M. A. Goodale and A. D. Milner, “Separate visual pathways for perception and action,” Trends Neurosci. 15, 20–25 (1992).
  36. J. Theeuwes, A. F. Kramer, S. Hahn, and D. E. Irwin, “Our eyes do not always go where we want them to go: capture of the eyes by new objects,” Psycholo. Sci. 9, 379–385 (1998).
  37. R. Desimone, J. Fleming, and C. G. Gross, “Prestriate afferents to inferior temporal cortex: an HRP study,” Brain Res. 184, 41–55 (1980).
  38. T. Moore, “Shape representations and visual guidance of saccadic eye movements,” Science 285, 1914–1917 (1999).
  39. U. Rajashekar, L. K. Cormak, and A. C. Bovik, “Visual search: structure from noise,” presented at the Symposium on Eye Tracking Research & Application 2002, New Orleans, La., March 25–27, 2002.
  40. M. P. Eckstein and A. J. Ahumada, Jr., “Classification images: a tool to analyze visual strategies,” J. Vision 2, 1x (2002).
  41. A. Ahumada, Jr., “Perceptual classification images from Vernier acuity masked by noise,” Perception 26 (supplement), 18 (1996).
  42. J. M. Gold, R. F. Murray, P. J. Bennett, and A. B. Sekuler, “Deriving behavioural receptive fields for visually completed contours,” Curr. Biol. 10, 663–666 (2000).
  43. A. B. Watson and R. Rosenholtz, “A Rorschach test for visual classification strategies,” Invest. Ophthalmol. Visual Sci. 38, S1 (1997).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited