Abstract

Just-noticeable differences (jnd’s) in velocity were measured as a function of reference velocity for central and peripheral vision. The velocity discrimination curves plotting jnd’s in velocity, expressed as Weber fractions, as a function of reference velocity were U shaped at all eccentricities. Under almost every stimulus condition the increase in jnd in velocity with increasing eccentricity was significantly larger at low reference velocities than at high reference velocities. Consequently the shift toward higher velocities with increasing eccentricity was much clearer for the lower end of the velocity-discrimination curve than for the upper end. These results are in agreement with the predictions derived from the response characteristics of velocity-tuned cells. Control experiments involving direction discrimination have shown that the impossibility of making fine velocity judgments at high speeds is due not to too weak a contrast for the stimulus motion to be visible but to a limitation in the neural apparatus analyzing velocity.

© 1985 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. W. A. van de Grind, A. J. van Doorn, J. J. Koenderink, “Detection of coherent movement in peripherally viewed random-dot patterns,” J. Opt. Soc. Am. 73, 1674–1683 (1983).
    [CrossRef] [PubMed]
  2. S. P. McKee, K. Nakayama, “The detection of motion in the peripheral visual field,” Vision Res. 24, 25–32.
    [PubMed]
  3. F. W. Weymouth, “Visual sensory units and the minimal angle of resolution,” Am. J. Ophthal. 46, 102–113 (1958).
    [PubMed]
  4. G. A. Orban, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
    [CrossRef] [PubMed]
  5. S. P. McKee, “A local mechanism for differential velocity detection,” Vision Res. 21, 491–500 (1981).
    [CrossRef] [PubMed]
  6. G. A. Orban, Neuronal Operations in the Visual Cortex, Vol. 11 of Studies of Brain Function, H. B. Barlow, T. H. Bullock, E. Forey, O. J. Grüsser, A. Peters, eds. (Springer-Verlag, Berlin, 1984).
    [CrossRef]
  7. G. A. Orban, H. Kennedy, H. Maes, “Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity,” J. Neurophysiol. 45, 1043–1058 (1981).
    [PubMed]
  8. J. H. R. Maunsell, d. C. Van Essen, “Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation,” J. Neurophysiol. 49, 1127–1147 (1983).
    [PubMed]
  9. B. De Bruyn, G. A. Orban, “Temporal summation in human velocity discrimination,” Arch. Int. Physiol. Biochim. 93(2), P11–P12 (1985).
  10. E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control. II. Single target displacements,” Vision Res. 19, 633–646. (1979).
    [CrossRef] [PubMed]
  11. G. Westheimer, “Eye movement responses to a horizontally moving visual stimulus,” AMA Arch. Ophthalmol. 52, 932–941 (1954).
    [CrossRef] [PubMed]
  12. G. B. Wethill, H. Levitt, “Sequential estimation of points on a psychometric function,” Brit. J. Math. Statist. Psychol. 18, 1–10 (1965).
    [CrossRef]
  13. A. P. Ginsburg, M. W. Cannon, “Comparison of three methods for rapid determination of threshold contrast sensitivity,” Invest. Ophthalmol. Vis. Sci. 24, 798–802 (1983).
    [PubMed]
  14. T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).
  15. V. Virsu, J. Rovamo, “Visual resolution, contrast sensitivity, and the cortical magnification factor,” Exp. Brain Res. 37, 475–494 (1979).
    [CrossRef] [PubMed]
  16. D. M. Levi, S. A. Klein, P. Aitsebaomo, “Detection and discrimination of the direction of motion in central and peripheral vision of normal and amblyopic observers,” Vision Res. 24, 789–800 (1984).
    [CrossRef] [PubMed]
  17. J. J. Koenderink, A. J. van Doorn, W. A. van de Grind, “Spatial and temporal parameters of motion detection in the peripheral visual field,” J. Opt. Soc. Am. A 2, 252–259 (1985).
    [CrossRef] [PubMed]
  18. G. A. Orban, J. Duysens, H. Maes, “Prediction of the optimal velocity of velocity tuned cells from their ON & OFF input,” Arch. Int. Physiol. Biochim. 93(1), P32–P33 (1985).
  19. J. Duysens, G. A. Orban, J. Cremieux, “Spatial and temporal constraints of direction selectivity in visual cortical neurones of the cat,” Arch. Int. Physiol. Biochim. 93(1), P5–P6 (1985).
  20. S. P. McKee, D. G. Taylor, “Discrimination of time: comparison of foveal and peripheral sensitivity,” J. Opt. Soc. Am. A 1, 620–627 (1984.)
    [CrossRef] [PubMed]
  21. G. Westheimer, “The spatial grain of the perifoveal visual,” Vision Res. 22, 157–162 (1982).
    [CrossRef]
  22. P. D. Tynan, R. Sekuler, “Motion processing in peripheral vision: reaction time and perceived velocity,” Vision Res. 22, 61–68 (1982).
    [CrossRef] [PubMed]

1985 (4)

B. De Bruyn, G. A. Orban, “Temporal summation in human velocity discrimination,” Arch. Int. Physiol. Biochim. 93(2), P11–P12 (1985).

J. J. Koenderink, A. J. van Doorn, W. A. van de Grind, “Spatial and temporal parameters of motion detection in the peripheral visual field,” J. Opt. Soc. Am. A 2, 252–259 (1985).
[CrossRef] [PubMed]

G. A. Orban, J. Duysens, H. Maes, “Prediction of the optimal velocity of velocity tuned cells from their ON & OFF input,” Arch. Int. Physiol. Biochim. 93(1), P32–P33 (1985).

J. Duysens, G. A. Orban, J. Cremieux, “Spatial and temporal constraints of direction selectivity in visual cortical neurones of the cat,” Arch. Int. Physiol. Biochim. 93(1), P5–P6 (1985).

1984 (4)

S. P. McKee, D. G. Taylor, “Discrimination of time: comparison of foveal and peripheral sensitivity,” J. Opt. Soc. Am. A 1, 620–627 (1984.)
[CrossRef] [PubMed]

T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).

D. M. Levi, S. A. Klein, P. Aitsebaomo, “Detection and discrimination of the direction of motion in central and peripheral vision of normal and amblyopic observers,” Vision Res. 24, 789–800 (1984).
[CrossRef] [PubMed]

G. A. Orban, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
[CrossRef] [PubMed]

1983 (3)

W. A. van de Grind, A. J. van Doorn, J. J. Koenderink, “Detection of coherent movement in peripherally viewed random-dot patterns,” J. Opt. Soc. Am. 73, 1674–1683 (1983).
[CrossRef] [PubMed]

J. H. R. Maunsell, d. C. Van Essen, “Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation,” J. Neurophysiol. 49, 1127–1147 (1983).
[PubMed]

A. P. Ginsburg, M. W. Cannon, “Comparison of three methods for rapid determination of threshold contrast sensitivity,” Invest. Ophthalmol. Vis. Sci. 24, 798–802 (1983).
[PubMed]

1982 (2)

G. Westheimer, “The spatial grain of the perifoveal visual,” Vision Res. 22, 157–162 (1982).
[CrossRef]

P. D. Tynan, R. Sekuler, “Motion processing in peripheral vision: reaction time and perceived velocity,” Vision Res. 22, 61–68 (1982).
[CrossRef] [PubMed]

1981 (2)

S. P. McKee, “A local mechanism for differential velocity detection,” Vision Res. 21, 491–500 (1981).
[CrossRef] [PubMed]

G. A. Orban, H. Kennedy, H. Maes, “Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity,” J. Neurophysiol. 45, 1043–1058 (1981).
[PubMed]

1979 (2)

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control. II. Single target displacements,” Vision Res. 19, 633–646. (1979).
[CrossRef] [PubMed]

V. Virsu, J. Rovamo, “Visual resolution, contrast sensitivity, and the cortical magnification factor,” Exp. Brain Res. 37, 475–494 (1979).
[CrossRef] [PubMed]

1965 (1)

G. B. Wethill, H. Levitt, “Sequential estimation of points on a psychometric function,” Brit. J. Math. Statist. Psychol. 18, 1–10 (1965).
[CrossRef]

1958 (1)

F. W. Weymouth, “Visual sensory units and the minimal angle of resolution,” Am. J. Ophthal. 46, 102–113 (1958).
[PubMed]

1954 (1)

G. Westheimer, “Eye movement responses to a horizontally moving visual stimulus,” AMA Arch. Ophthalmol. 52, 932–941 (1954).
[CrossRef] [PubMed]

Aitsebaomo, P.

D. M. Levi, S. A. Klein, P. Aitsebaomo, “Detection and discrimination of the direction of motion in central and peripheral vision of normal and amblyopic observers,” Vision Res. 24, 789–800 (1984).
[CrossRef] [PubMed]

Cannon, M. W.

A. P. Ginsburg, M. W. Cannon, “Comparison of three methods for rapid determination of threshold contrast sensitivity,” Invest. Ophthalmol. Vis. Sci. 24, 798–802 (1983).
[PubMed]

Cremieux, J.

J. Duysens, G. A. Orban, J. Cremieux, “Spatial and temporal constraints of direction selectivity in visual cortical neurones of the cat,” Arch. Int. Physiol. Biochim. 93(1), P5–P6 (1985).

De Bruyn, B.

B. De Bruyn, G. A. Orban, “Temporal summation in human velocity discrimination,” Arch. Int. Physiol. Biochim. 93(2), P11–P12 (1985).

de Wolf, J.

G. A. Orban, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
[CrossRef] [PubMed]

Duysens, J.

G. A. Orban, J. Duysens, H. Maes, “Prediction of the optimal velocity of velocity tuned cells from their ON & OFF input,” Arch. Int. Physiol. Biochim. 93(1), P32–P33 (1985).

J. Duysens, G. A. Orban, J. Cremieux, “Spatial and temporal constraints of direction selectivity in visual cortical neurones of the cat,” Arch. Int. Physiol. Biochim. 93(1), P5–P6 (1985).

Ginsburg, A. P.

A. P. Ginsburg, M. W. Cannon, “Comparison of three methods for rapid determination of threshold contrast sensitivity,” Invest. Ophthalmol. Vis. Sci. 24, 798–802 (1983).
[PubMed]

Gizzi, M. S.

T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).

Kennedy, H.

G. A. Orban, H. Kennedy, H. Maes, “Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity,” J. Neurophysiol. 45, 1043–1058 (1981).
[PubMed]

Klein, S. A.

D. M. Levi, S. A. Klein, P. Aitsebaomo, “Detection and discrimination of the direction of motion in central and peripheral vision of normal and amblyopic observers,” Vision Res. 24, 789–800 (1984).
[CrossRef] [PubMed]

Koenderink, J. J.

Kowler, E.

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control. II. Single target displacements,” Vision Res. 19, 633–646. (1979).
[CrossRef] [PubMed]

Levi, D. M.

D. M. Levi, S. A. Klein, P. Aitsebaomo, “Detection and discrimination of the direction of motion in central and peripheral vision of normal and amblyopic observers,” Vision Res. 24, 789–800 (1984).
[CrossRef] [PubMed]

Levitt, H.

G. B. Wethill, H. Levitt, “Sequential estimation of points on a psychometric function,” Brit. J. Math. Statist. Psychol. 18, 1–10 (1965).
[CrossRef]

Maes, H.

G. A. Orban, J. Duysens, H. Maes, “Prediction of the optimal velocity of velocity tuned cells from their ON & OFF input,” Arch. Int. Physiol. Biochim. 93(1), P32–P33 (1985).

G. A. Orban, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
[CrossRef] [PubMed]

G. A. Orban, H. Kennedy, H. Maes, “Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity,” J. Neurophysiol. 45, 1043–1058 (1981).
[PubMed]

Maunsell, J. H. R.

J. H. R. Maunsell, d. C. Van Essen, “Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation,” J. Neurophysiol. 49, 1127–1147 (1983).
[PubMed]

McKee, S. P.

S. P. McKee, D. G. Taylor, “Discrimination of time: comparison of foveal and peripheral sensitivity,” J. Opt. Soc. Am. A 1, 620–627 (1984.)
[CrossRef] [PubMed]

S. P. McKee, “A local mechanism for differential velocity detection,” Vision Res. 21, 491–500 (1981).
[CrossRef] [PubMed]

S. P. McKee, K. Nakayama, “The detection of motion in the peripheral visual field,” Vision Res. 24, 25–32.
[PubMed]

Movshon, J. A.

T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).

Nakayama, K.

S. P. McKee, K. Nakayama, “The detection of motion in the peripheral visual field,” Vision Res. 24, 25–32.
[PubMed]

Orban, G. A.

B. De Bruyn, G. A. Orban, “Temporal summation in human velocity discrimination,” Arch. Int. Physiol. Biochim. 93(2), P11–P12 (1985).

J. Duysens, G. A. Orban, J. Cremieux, “Spatial and temporal constraints of direction selectivity in visual cortical neurones of the cat,” Arch. Int. Physiol. Biochim. 93(1), P5–P6 (1985).

G. A. Orban, J. Duysens, H. Maes, “Prediction of the optimal velocity of velocity tuned cells from their ON & OFF input,” Arch. Int. Physiol. Biochim. 93(1), P32–P33 (1985).

G. A. Orban, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
[CrossRef] [PubMed]

G. A. Orban, H. Kennedy, H. Maes, “Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity,” J. Neurophysiol. 45, 1043–1058 (1981).
[PubMed]

G. A. Orban, Neuronal Operations in the Visual Cortex, Vol. 11 of Studies of Brain Function, H. B. Barlow, T. H. Bullock, E. Forey, O. J. Grüsser, A. Peters, eds. (Springer-Verlag, Berlin, 1984).
[CrossRef]

Pasternak, T.

T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).

Rovamo, J.

V. Virsu, J. Rovamo, “Visual resolution, contrast sensitivity, and the cortical magnification factor,” Exp. Brain Res. 37, 475–494 (1979).
[CrossRef] [PubMed]

Schumer, R. A.

T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).

Sekuler, R.

P. D. Tynan, R. Sekuler, “Motion processing in peripheral vision: reaction time and perceived velocity,” Vision Res. 22, 61–68 (1982).
[CrossRef] [PubMed]

Steinman, R. M.

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control. II. Single target displacements,” Vision Res. 19, 633–646. (1979).
[CrossRef] [PubMed]

Taylor, D. G.

Tynan, P. D.

P. D. Tynan, R. Sekuler, “Motion processing in peripheral vision: reaction time and perceived velocity,” Vision Res. 22, 61–68 (1982).
[CrossRef] [PubMed]

van de Grind, W. A.

van Doorn, A. J.

Van Essen, d. C.

J. H. R. Maunsell, d. C. Van Essen, “Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation,” J. Neurophysiol. 49, 1127–1147 (1983).
[PubMed]

Virsu, V.

V. Virsu, J. Rovamo, “Visual resolution, contrast sensitivity, and the cortical magnification factor,” Exp. Brain Res. 37, 475–494 (1979).
[CrossRef] [PubMed]

Westheimer, G.

G. Westheimer, “The spatial grain of the perifoveal visual,” Vision Res. 22, 157–162 (1982).
[CrossRef]

G. Westheimer, “Eye movement responses to a horizontally moving visual stimulus,” AMA Arch. Ophthalmol. 52, 932–941 (1954).
[CrossRef] [PubMed]

Wethill, G. B.

G. B. Wethill, H. Levitt, “Sequential estimation of points on a psychometric function,” Brit. J. Math. Statist. Psychol. 18, 1–10 (1965).
[CrossRef]

Weymouth, F. W.

F. W. Weymouth, “Visual sensory units and the minimal angle of resolution,” Am. J. Ophthal. 46, 102–113 (1958).
[PubMed]

Am. J. Ophthal. (1)

F. W. Weymouth, “Visual sensory units and the minimal angle of resolution,” Am. J. Ophthal. 46, 102–113 (1958).
[PubMed]

AMA Arch. Ophthalmol. (1)

G. Westheimer, “Eye movement responses to a horizontally moving visual stimulus,” AMA Arch. Ophthalmol. 52, 932–941 (1954).
[CrossRef] [PubMed]

Arch. Int. Physiol. Biochim. (3)

B. De Bruyn, G. A. Orban, “Temporal summation in human velocity discrimination,” Arch. Int. Physiol. Biochim. 93(2), P11–P12 (1985).

G. A. Orban, J. Duysens, H. Maes, “Prediction of the optimal velocity of velocity tuned cells from their ON & OFF input,” Arch. Int. Physiol. Biochim. 93(1), P32–P33 (1985).

J. Duysens, G. A. Orban, J. Cremieux, “Spatial and temporal constraints of direction selectivity in visual cortical neurones of the cat,” Arch. Int. Physiol. Biochim. 93(1), P5–P6 (1985).

Brit. J. Math. Statist. Psychol. (1)

G. B. Wethill, H. Levitt, “Sequential estimation of points on a psychometric function,” Brit. J. Math. Statist. Psychol. 18, 1–10 (1965).
[CrossRef]

Exp. Brain Res. (1)

V. Virsu, J. Rovamo, “Visual resolution, contrast sensitivity, and the cortical magnification factor,” Exp. Brain Res. 37, 475–494 (1979).
[CrossRef] [PubMed]

Invest. Ophthalmol. Vis. Sci. (1)

A. P. Ginsburg, M. W. Cannon, “Comparison of three methods for rapid determination of threshold contrast sensitivity,” Invest. Ophthalmol. Vis. Sci. 24, 798–802 (1983).
[PubMed]

J. Neurophysiol. (2)

G. A. Orban, H. Kennedy, H. Maes, “Response to movement of neurons in areas 17 and 18 of the cat: velocity sensitivity,” J. Neurophysiol. 45, 1043–1058 (1981).
[PubMed]

J. H. R. Maunsell, d. C. Van Essen, “Functional properties of neurons in middle temporal visual area of the macaque monkey. I. Selectivity for stimulus direction, speed, and orientation,” J. Neurophysiol. 49, 1127–1147 (1983).
[PubMed]

J. Opt. Soc. Am. (1)

J. Opt. Soc. Am. A (2)

Soc. Neurosci. Abstr. (1)

T. Pasternak, R. A. Schumer, M. S. Gizzi, J. A. Movshon, “Abolition of cortical directional selectivity impairs direction discrimination of cats,” Soc. Neurosci. Abstr. 10, 799 (1984).

Vision Res. (7)

D. M. Levi, S. A. Klein, P. Aitsebaomo, “Detection and discrimination of the direction of motion in central and peripheral vision of normal and amblyopic observers,” Vision Res. 24, 789–800 (1984).
[CrossRef] [PubMed]

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control. II. Single target displacements,” Vision Res. 19, 633–646. (1979).
[CrossRef] [PubMed]

S. P. McKee, K. Nakayama, “The detection of motion in the peripheral visual field,” Vision Res. 24, 25–32.
[PubMed]

G. A. Orban, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
[CrossRef] [PubMed]

S. P. McKee, “A local mechanism for differential velocity detection,” Vision Res. 21, 491–500 (1981).
[CrossRef] [PubMed]

G. Westheimer, “The spatial grain of the perifoveal visual,” Vision Res. 22, 157–162 (1982).
[CrossRef]

P. D. Tynan, R. Sekuler, “Motion processing in peripheral vision: reaction time and perceived velocity,” Vision Res. 22, 61–68 (1982).
[CrossRef] [PubMed]

Other (1)

G. A. Orban, Neuronal Operations in the Visual Cortex, Vol. 11 of Studies of Brain Function, H. B. Barlow, T. H. Bullock, E. Forey, O. J. Grüsser, A. Peters, eds. (Springer-Verlag, Berlin, 1984).
[CrossRef]

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (7)

Fig. 1
Fig. 1

Comparison of velocity discrimination curves obtained with the method of single stimuli (MSS) and with the transformed up–down method (TUDM). The differential thresholds of jnd’s in velocity are expressed as Weber fractions and plotted as a function of reference velocity. A and B, mean 75% thresholds obtained for central vision with the SS method in a previous study4 with a slit width of 0.2° (A, n = 3) and in the present study with a slit width of 0.1° (B, n = 2); C, comparison of thresholds obtained for central vision (slit width 0.1°) with the TUDM tracking a 84% correct level (mean of three subjects, B.G., B.D.B., and V.B.) with the 84% level obtained with the SS method (mean of two subjects, B.D.B. and V.B.). D, comparison of thresholds for subject B.D.B. at 20° eccentricity. The agreement between the SS method and TUDM thresholds is good although the TUDM yields systematically lower thresholds than the SS method at low velocities. Vertical bars in A and C indicate standard deviations.

Fig. 2
Fig. 2

Comparison of velocity discrimination at different retinal loci: 30° below and 30° above the fixation point on the vertical meridian and 30° right of the fixation point on the horizontal meridian for binocular and monocular viewing conditions. Same conventions as in Fig 1. Subject F.V.C., slit width 0.1°, and high contrast (log ΔI/I = 3.64).

Fig. 3
Fig. 3

Velocity discrimination at different eccentricities. Same conventions as in Fig. 1. Condition 1, high contrast (log ΔI/I = 3.64) and fixed slit width (0.1°); condition 2, high contrast and slit width scaled according to MAR; condition 3, low contrast (log ΔI/I = –0.63) and slit width scaled according to MAR. Note that in condition 2 thresholds for more peripherally viewed slits could not be determined at the slowest speeds because of window width limitations.

Fig. 4
Fig. 4

jnd’s in velocity expressed as Weber fractions plotted as a function of eccentricity for a slow (4°/sec) and a fast (64°/sec) reference velocity. Subjects F.V.C. and V.B. were tested with the SS method, subjects D.G. and B.D.B. with the TUD method. The results of F.V.C. and the first set of results of B.D.B. (indicated by filled circles and crosses) are derived from Fig. 3. Notice the good agreement between the two sets of jnd’s obtained for subject B.D.B. at a several-month interval.

Fig. 5
Fig. 5

Comparison of the resolution ratio (acuity) and the scale factor necessary to make the lower branch (A, B) and upper branch (D, E) of the velocity discrimination curves coincident for the three conditions of Fig. 3 and subjects B.D.B. (A, D) and F.V.C. (B, E). Inset (C): example of fit between central and peripheral branches after scaling. Notice the difference in scale between upper and lower panels.

Fig. 6
Fig. 6

Differential duration threshold expressed as Weber fractions plotted as a function of reference duration at different eccentricities for high contrast (A) and low contrast (B). Subject F.V.C., slit width 0.55°.

Fig. 7
Fig. 7

Direction discrimination at different eccentricities. Same conditions as in Fig. 3 except that for subject L.D.B. the low contrast was somewhat higher, log ΔI/I = –0.2.

Tables (2)

Tables Icon

Table 1 Stimulus Conditions

Tables Icon

Table 2 Analysis of Variance: Simple Main Effects of Eccentricity at Different Reference Velocitiesa

Metrics