Abstract

Human observers can discriminate a 5% difference in velocity for a wide range of velocities. Using an apparent-motion stimulus, we demonstrated that velocity discrimination depends on the detection of small changes in asynchrony, changes of the order of 1 msec or less. The simplest component of an apparent-motion stimulus is a pair of spatially separate lines presented asynchronously. Generally the incremental asynchrony threshold for a single pair of lines is much too large to account for velocity discrimination. A sequence of five to eight asynchronously presented targets, equivalent to continuous motion viewed for a duration of 80–100 msec, is required to reach asymptotic velocity discrimination. Our experiments rule out probability summation as the explanation for the enhanced temporal sensitivity observed with the sequential presentation of multiple asynchronous targets. Sequential recruitment, a descriptive term for this enhanced temporal sensitivity, depends on the summation of a velocity-specific signal within the physiological network responding to motion.

© 1985 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. S. P. McKee, “A local mechanism for differential velocity detection,” Vision Res. 21, 491–500 (1981).
    [Crossref] [PubMed]
  2. E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control—III. Guessing unpredictable target displacements,” Vision Res. 21, 191–204 (1981).
    [Crossref]
  3. A. B. Watson, A. Ahumada, J. E. Farrell, “The window of visibility: a psychophysical theory of fidelity in time-sampled visual motion displays,” NASA Tech. Paper 2211 (1983).
  4. S. P. McKee, D. G. Taylor, “The discrimination of time: a comparison of foveal and peripheral sensitivity,” J. Opt. Soc. Am. A 1, 620–627 (1984).
    [Crossref] [PubMed]
  5. D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).
  6. The numbers labeled PROBABILITY SUMMATION in Fig. 3 were calculated from the measured psychometric functions for each subject. These functions described the detectability of various increments (Δt) added to either a basic 10-msec asynchrony or a basic 20-msec asynchrony. We asked what the summed detectability is of an increment added to one 20-msec interval plus half of that increment added to two 10-msec intervals. As an example, consider the data of subject SM for a single 20-msec interval (shown in the second column). This results shows that 6.8 msec added to 20 msec has a detectability (d′) of 0.68, our threshold criterion. If two 10-msec intervals of 9-min separation were wedged into the 20-msec interval separated by 18 min, then each 10-msec interval would have half of the added 6.8 increment, or an incremental change of 3.4 msec, because that is how the timing for the triplet of lines shown in the third column was distributed. From the 10-msec psychometric function for subject SM we then estimated the detectability of 3.4 msec and found it to be a d′ value of 0.613. Using the formula for the integration model, we then estimated the summed detectability of the three increments:d′sum=[(0.613)2+(0.613)2+(0.68)2]1/2.This calculation shows that the summed detectability of 6.8 msec for three intervals has been increased from 0.68 to 1.1. If 6.8 msec corresponds to a detectability of 1.1, what incremental change would produce a threshold d′ of 0.68? As the psychometric functions are well fitted by cumulative normal functions, we used probability paper to extrapolate down linearly to the appropriate threshold increment, which for this subject corresponds to 4 msec. Note that the third column for Fig. 3 reports the real threshold detected by a subject viewing the triplet stimulus, which for this subject is 3.4 msec.
  7. J. Cremieux, G. A. Orban, J. Duysens, “Response of cat visual cortical cells to continuously and stroboscopically illuminated moving light slits compared,” Vision Res. 24, 449–457 (1984).
    [Crossref]
  8. D. H. Kelly, “Theory of flicker and transient responses. I. Uniform fields,” J. Opt. Soc. Am. 61, 537–546 (1971).
    [Crossref] [PubMed]
  9. A. B. Watson, “Derivation of the impulse response: comments on the method of Roufs and Blommaert,” Vision Res. 22, 1335–1337 (1982).
    [Crossref] [PubMed]
  10. R. G. Bennett, G. Westheimer, “A shift in the perceived simultaneity of adjacent visual stimuli following adaptation to stroboscopic motion along the same axis,” Vision Res. (to be published).
  11. G. Westheimer, “Temporal order detection for foveal and peripheral visual stimuli,” Vision Res. 23, 759–764 (1983).
    [Crossref] [PubMed]
  12. G. A. Organ, J. de Wolf, H. Maes, “Factors influencing velocity coding in the human visual system,” Vision Res. 24, 33–39 (1984).
    [Crossref]
  13. J. P. H. Van Santen, G. Sperling, “Temporal covariance model of human motion perception,” J. Opt. Soc. AM. A 1, 451–473 (1984).
    [Crossref] [PubMed]
  14. G. A. Orban, “Velocity tuned cortical cells and human velocity discrimination,” in Brain Mechanisms of Spatial Vision, D. J. Ingle, M. Jeannerod, D. N. Lee, eds. (Martinus Nijhof, La Haye, The Netherlands, 1984).
  15. H. B. Barlow, W. R. Levick, “The mechanism of directionally selective units in rabbit’s retina,” J. Physiol. 178, 477–504 (1965).
    [PubMed]
  16. J. A. Movshon, I. D. Thompson, D. J. Tolhurst, “Receptive field organization of complex cells in the cat’s striate cortex, 283, 79–99 (1978).
  17. G. A. Orban, Katholieke Universiteit de Leuven, Leuven, Belgium, “Processing of moving images in geniculo-cortical pathway” ( personal communication, 1984).
  18. H. J. Wyatt, N. W. Daw, “Directionally sensitive ganglion cells in the rabbit retina: specificity for stimulus direction, size and speed,” J. Neurophysiol. 38, 613–626 (1975).
    [PubMed]
  19. K. Nakayama, G. H. Silverman, “Temporal and spatial characteristics of the upper displacement limit for motion in random dots,” Vision Res. 24, 293–300 (1984).
    [Crossref] [PubMed]
  20. J. S. Lappin, M. A. Fuqua, “Nonlinear recruitment in the visual detection of moving patterns,” Invest. Ophthal. Vis. Sci. Suppl. 22, 123 (1982).

1984 (5)

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

J. Cremieux, G. A. Orban, J. Duysens, “Response of cat visual cortical cells to continuously and stroboscopically illuminated moving light slits compared,” Vision Res. 24, 449–457 (1984).
[Crossref]

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

J. P. H. Van Santen, G. Sperling, “Temporal covariance model of human motion perception,” J. Opt. Soc. AM. A 1, 451–473 (1984).
[Crossref] [PubMed]

K. Nakayama, G. H. Silverman, “Temporal and spatial characteristics of the upper displacement limit for motion in random dots,” Vision Res. 24, 293–300 (1984).
[Crossref] [PubMed]

1983 (1)

G. Westheimer, “Temporal order detection for foveal and peripheral visual stimuli,” Vision Res. 23, 759–764 (1983).
[Crossref] [PubMed]

1982 (2)

A. B. Watson, “Derivation of the impulse response: comments on the method of Roufs and Blommaert,” Vision Res. 22, 1335–1337 (1982).
[Crossref] [PubMed]

J. S. Lappin, M. A. Fuqua, “Nonlinear recruitment in the visual detection of moving patterns,” Invest. Ophthal. Vis. Sci. Suppl. 22, 123 (1982).

1981 (2)

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

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control—III. Guessing unpredictable target displacements,” Vision Res. 21, 191–204 (1981).
[Crossref]

1978 (1)

J. A. Movshon, I. D. Thompson, D. J. Tolhurst, “Receptive field organization of complex cells in the cat’s striate cortex, 283, 79–99 (1978).

1975 (1)

H. J. Wyatt, N. W. Daw, “Directionally sensitive ganglion cells in the rabbit retina: specificity for stimulus direction, size and speed,” J. Neurophysiol. 38, 613–626 (1975).
[PubMed]

1971 (1)

1965 (1)

H. B. Barlow, W. R. Levick, “The mechanism of directionally selective units in rabbit’s retina,” J. Physiol. 178, 477–504 (1965).
[PubMed]

Ahumada, A.

A. B. Watson, A. Ahumada, J. E. Farrell, “The window of visibility: a psychophysical theory of fidelity in time-sampled visual motion displays,” NASA Tech. Paper 2211 (1983).

Barlow, H. B.

H. B. Barlow, W. R. Levick, “The mechanism of directionally selective units in rabbit’s retina,” J. Physiol. 178, 477–504 (1965).
[PubMed]

Bennett, R. G.

R. G. Bennett, G. Westheimer, “A shift in the perceived simultaneity of adjacent visual stimuli following adaptation to stroboscopic motion along the same axis,” Vision Res. (to be published).

Cremieux, J.

J. Cremieux, G. A. Orban, J. Duysens, “Response of cat visual cortical cells to continuously and stroboscopically illuminated moving light slits compared,” Vision Res. 24, 449–457 (1984).
[Crossref]

Daw, N. W.

H. J. Wyatt, N. W. Daw, “Directionally sensitive ganglion cells in the rabbit retina: specificity for stimulus direction, size and speed,” J. Neurophysiol. 38, 613–626 (1975).
[PubMed]

de Wolf, J.

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

Duysens, J.

J. Cremieux, G. A. Orban, J. Duysens, “Response of cat visual cortical cells to continuously and stroboscopically illuminated moving light slits compared,” Vision Res. 24, 449–457 (1984).
[Crossref]

Farrell, J. E.

A. B. Watson, A. Ahumada, J. E. Farrell, “The window of visibility: a psychophysical theory of fidelity in time-sampled visual motion displays,” NASA Tech. Paper 2211 (1983).

Fuqua, M. A.

J. S. Lappin, M. A. Fuqua, “Nonlinear recruitment in the visual detection of moving patterns,” Invest. Ophthal. Vis. Sci. Suppl. 22, 123 (1982).

Green, D. M.

D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).

Kelly, D. H.

Kowler, E.

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control—III. Guessing unpredictable target displacements,” Vision Res. 21, 191–204 (1981).
[Crossref]

Lappin, J. S.

J. S. Lappin, M. A. Fuqua, “Nonlinear recruitment in the visual detection of moving patterns,” Invest. Ophthal. Vis. Sci. Suppl. 22, 123 (1982).

Levick, W. R.

H. B. Barlow, W. R. Levick, “The mechanism of directionally selective units in rabbit’s retina,” J. Physiol. 178, 477–504 (1965).
[PubMed]

Maes, H.

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

McKee, S. P.

Movshon, J. A.

J. A. Movshon, I. D. Thompson, D. J. Tolhurst, “Receptive field organization of complex cells in the cat’s striate cortex, 283, 79–99 (1978).

Nakayama, K.

K. Nakayama, G. H. Silverman, “Temporal and spatial characteristics of the upper displacement limit for motion in random dots,” Vision Res. 24, 293–300 (1984).
[Crossref] [PubMed]

Orban, G. A.

J. Cremieux, G. A. Orban, J. Duysens, “Response of cat visual cortical cells to continuously and stroboscopically illuminated moving light slits compared,” Vision Res. 24, 449–457 (1984).
[Crossref]

G. A. Orban, Katholieke Universiteit de Leuven, Leuven, Belgium, “Processing of moving images in geniculo-cortical pathway” ( personal communication, 1984).

G. A. Orban, “Velocity tuned cortical cells and human velocity discrimination,” in Brain Mechanisms of Spatial Vision, D. J. Ingle, M. Jeannerod, D. N. Lee, eds. (Martinus Nijhof, La Haye, The Netherlands, 1984).

Organ, G. A.

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

Silverman, G. H.

K. Nakayama, G. H. Silverman, “Temporal and spatial characteristics of the upper displacement limit for motion in random dots,” Vision Res. 24, 293–300 (1984).
[Crossref] [PubMed]

Sperling, G.

Steinman, R. M.

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control—III. Guessing unpredictable target displacements,” Vision Res. 21, 191–204 (1981).
[Crossref]

Swets, J. A.

D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).

Taylor, D. G.

Thompson, I. D.

J. A. Movshon, I. D. Thompson, D. J. Tolhurst, “Receptive field organization of complex cells in the cat’s striate cortex, 283, 79–99 (1978).

Tolhurst, D. J.

J. A. Movshon, I. D. Thompson, D. J. Tolhurst, “Receptive field organization of complex cells in the cat’s striate cortex, 283, 79–99 (1978).

Van Santen, J. P. H.

Watson, A. B.

A. B. Watson, “Derivation of the impulse response: comments on the method of Roufs and Blommaert,” Vision Res. 22, 1335–1337 (1982).
[Crossref] [PubMed]

A. B. Watson, A. Ahumada, J. E. Farrell, “The window of visibility: a psychophysical theory of fidelity in time-sampled visual motion displays,” NASA Tech. Paper 2211 (1983).

Westheimer, G.

G. Westheimer, “Temporal order detection for foveal and peripheral visual stimuli,” Vision Res. 23, 759–764 (1983).
[Crossref] [PubMed]

R. G. Bennett, G. Westheimer, “A shift in the perceived simultaneity of adjacent visual stimuli following adaptation to stroboscopic motion along the same axis,” Vision Res. (to be published).

Wyatt, H. J.

H. J. Wyatt, N. W. Daw, “Directionally sensitive ganglion cells in the rabbit retina: specificity for stimulus direction, size and speed,” J. Neurophysiol. 38, 613–626 (1975).
[PubMed]

Invest. Ophthal. Vis. Sci. Suppl. (1)

J. S. Lappin, M. A. Fuqua, “Nonlinear recruitment in the visual detection of moving patterns,” Invest. Ophthal. Vis. Sci. Suppl. 22, 123 (1982).

J. Neurophysiol. (1)

H. J. Wyatt, N. W. Daw, “Directionally sensitive ganglion cells in the rabbit retina: specificity for stimulus direction, size and speed,” J. Neurophysiol. 38, 613–626 (1975).
[PubMed]

J. Opt. Soc. Am. (1)

J. Opt. Soc. AM. A (1)

J. Physiol. (1)

H. B. Barlow, W. R. Levick, “The mechanism of directionally selective units in rabbit’s retina,” J. Physiol. 178, 477–504 (1965).
[PubMed]

Receptive field organization of complex cells in the cat’s striate cortex (1)

J. A. Movshon, I. D. Thompson, D. J. Tolhurst, “Receptive field organization of complex cells in the cat’s striate cortex, 283, 79–99 (1978).

Vision Res. (7)

K. Nakayama, G. H. Silverman, “Temporal and spatial characteristics of the upper displacement limit for motion in random dots,” Vision Res. 24, 293–300 (1984).
[Crossref] [PubMed]

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

E. Kowler, R. M. Steinman, “The effect of expectations on slow oculomotor control—III. Guessing unpredictable target displacements,” Vision Res. 21, 191–204 (1981).
[Crossref]

J. Cremieux, G. A. Orban, J. Duysens, “Response of cat visual cortical cells to continuously and stroboscopically illuminated moving light slits compared,” Vision Res. 24, 449–457 (1984).
[Crossref]

A. B. Watson, “Derivation of the impulse response: comments on the method of Roufs and Blommaert,” Vision Res. 22, 1335–1337 (1982).
[Crossref] [PubMed]

G. Westheimer, “Temporal order detection for foveal and peripheral visual stimuli,” Vision Res. 23, 759–764 (1983).
[Crossref] [PubMed]

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

Other (6)

G. A. Orban, “Velocity tuned cortical cells and human velocity discrimination,” in Brain Mechanisms of Spatial Vision, D. J. Ingle, M. Jeannerod, D. N. Lee, eds. (Martinus Nijhof, La Haye, The Netherlands, 1984).

R. G. Bennett, G. Westheimer, “A shift in the perceived simultaneity of adjacent visual stimuli following adaptation to stroboscopic motion along the same axis,” Vision Res. (to be published).

A. B. Watson, A. Ahumada, J. E. Farrell, “The window of visibility: a psychophysical theory of fidelity in time-sampled visual motion displays,” NASA Tech. Paper 2211 (1983).

D. M. Green, J. A. Swets, Signal Detection Theory and Psychophysics (Wiley, New York, 1966).

The numbers labeled PROBABILITY SUMMATION in Fig. 3 were calculated from the measured psychometric functions for each subject. These functions described the detectability of various increments (Δt) added to either a basic 10-msec asynchrony or a basic 20-msec asynchrony. We asked what the summed detectability is of an increment added to one 20-msec interval plus half of that increment added to two 10-msec intervals. As an example, consider the data of subject SM for a single 20-msec interval (shown in the second column). This results shows that 6.8 msec added to 20 msec has a detectability (d′) of 0.68, our threshold criterion. If two 10-msec intervals of 9-min separation were wedged into the 20-msec interval separated by 18 min, then each 10-msec interval would have half of the added 6.8 increment, or an incremental change of 3.4 msec, because that is how the timing for the triplet of lines shown in the third column was distributed. From the 10-msec psychometric function for subject SM we then estimated the detectability of 3.4 msec and found it to be a d′ value of 0.613. Using the formula for the integration model, we then estimated the summed detectability of the three increments:d′sum=[(0.613)2+(0.613)2+(0.68)2]1/2.This calculation shows that the summed detectability of 6.8 msec for three intervals has been increased from 0.68 to 1.1. If 6.8 msec corresponds to a detectability of 1.1, what incremental change would produce a threshold d′ of 0.68? As the psychometric functions are well fitted by cumulative normal functions, we used probability paper to extrapolate down linearly to the appropriate threshold increment, which for this subject corresponds to 4 msec. Note that the third column for Fig. 3 reports the real threshold detected by a subject viewing the triplet stimulus, which for this subject is 3.4 msec.

G. A. Orban, Katholieke Universiteit de Leuven, Leuven, Belgium, “Processing of moving images in geniculo-cortical pathway” ( personal communication, 1984).

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 (9)

Fig. 1
Fig. 1

Velocity increment-threshold factors for apparent motion (9 min of arc/10 msec; circles) and for continuous motion (54 sec of arc/1 msec; crosses) plotted as a function of duration. Subjects asked to judge whether the target moved faster or slower than the mean velocity. Mean velocity 15 deg/sec, target lines 9 min of arc long. Pattern of improvement with increasing duration is equivalent for apparent motion and continuous motion.

Fig. 2
Fig. 2

Thresholds for targets moving a fixed distance on each trial and for targets where distance traversed varied randomly from trial to trial. Fixed distance equalled 2.1 deg; duration (mean, 140 msec) covaried with the velocity variations of ±10% (e.g., from 126 to 154 msec). Average duration of the random distance was the same, 140 msec, but was varied independently of the velocity variations by ±20% (from 112 to 168 msec). Variations in overall duration are not the basis of these thresholds for either continuous or apparent motion.

Fig. 3
Fig. 3

Asynchrony increment thresholds for the three-line sequence, its components, and the thresholds predicted by probability summation. The components of the three-line sequence are two two-line intervals of 9 min of arc, 10 msec, and one two-line interval of 18 min of arc, 20 msec, defined by the outer lines of the three-line stimulus. Probability-summation calculations are based on these three temporal intervals. At the bottom of the table are the average thresholds for the four subjects expressed as percentages of the total temporal interval and as factors.

Fig. 4
Fig. 4

Comparison between the increment thresholds for the three-line sequential configuration and for a configuration in which the components of the three-line sequence are segregated vertically. The three leftmost bars of the stimultaneous configuration come on at the same time, followed 10 msec later by the two right lines of the two bottom pairs, followed another 10 msec later (20 msec total) by the right line of the top pair. Target lines 9 min of arc long separated vertically by 10 min of arc for total vertical length of 47 min of arc. Average thresholds are expressed as percentages of the 20-msec interval and as factors. The simultaneous configuration is not an adequate substitute for the sequential configuration.

Fig. 5
Fig. 5

Comparison between the increment thresholds for a 10-msec asynchrony for the three-line sequential stimulus and for three successive observations of a two-line 9-min-of-arc, 10-msec stimulus. The three successive presentations in the same place are separated temporally by 174 msec.

Fig. 6
Fig. 6

Asynchrony increment thresholds for apparent motion. In one condition, line spacing was fixed on each trial, and, for the other condition, spacing was varied randomly from trial to trial. The optimum separation for each subject was used; fixed spacing for ST and LW (6 min of arc, 10 msec) and for SM (9 min of arc, 10 msec). Variable spacing centered around the same optimal separation and had values of 4.5, 6, and 7.5 min of arc for ST, from 3.75 to 8.25 min of arc in 7 steps for LW, from 6.75 to 11.25 min of arc in seven steps for SM. The total duration for both fixed and variable spacing varied ±20% around 140 msec. The variable spacing and the variable velocity that it creates degrade temporal sensitivity.

Fig. 7
Fig. 7

Thresholds for continuous motion (18 arc sec/1 msec; crosses) and apparent motion (6 min of arc/20 msec; circles) plotted as a function of duration. Mean velocity, 5 deg/sec. Velocity discrimination thresholds reach a minimum in about 100 msec.

Fig. 8
Fig. 8

Thresholds for apparent motion with 10-msec intervals, velocity 15 deg/sec (circles), and apparent motion with 100-msec intervals, velocity 1.5 deg/sec (triangles), plotted as a function of the number of lines presented. Thresholds for the 100-msec intervals show only weak improvement with the addition of more lines. The square point for subject LW is the velocity threshold for continuous motion at 1.5 deg/sec (700-msec duration). For this temporal sampling rate (9 min/100 msec), apparent motion is not equivalent to continuous motion.

Fig. 9
Fig. 9

Comparison between the asynchrony increment thresholds, expressed as proportional values, for a sequential three-line stimulus (triplet) and for a temporal sequence combining orthogonal directions. Target lines 9 min of arc long, temporal interval 10 msec. In the left-hand target, the second line appears above the first (vertical gap 3 min of arc), followed by a third line 9 min to the right of the first. The configuration combining orthogonal directions of motion shows no sequential recruitment.

Equations (2)

Equations on this page are rendered with MathJax. Learn more.

d sum = [ d Δ t 2 ( 10 msec ) + d Δ t 2 ( 10 msec ) + d Δ t 2 ( 20 msec ) ] 1 / 2
dsum=[(0.613)2+(0.613)2+(0.68)2]1/2.

Metrics