Abstract

A study of the eye-movement control system shows the dependence of many of the system parameters on target luminance and contrast. Saccadic reaction time was found to decrease from a high value toward a fixed minimum as target luminance was increased, whether with a zero background (high contrast) or a fixed low contrast with respect to the background. The magnitude of the visual dead zone created when target luminance went below foveal threshold was also measured as a function of target luminance. The closed-loop gain of the eye-movement control system for ±2° sinusoidal target motion was measured as a function of luminance for high- and low-contrast targets. The results showed two changes of system gain as target luminance was decreased: (a) There was a decrease of the high-frequency response associated with target energies (luminance-by-time products) falling below a critical value required to produce visual sensation, resulting in a cutoff frequency; (b) for high-contrast targets only, there was an over-all decrease of system gain as target luminance was decreased, for luminances well above foveal threshold and for frequencies well below cutoff. This latter, unexplained effect cannot be interpreted as resulting from an increase of retinal latency, the effect of a visual dead zone, or the lack of sufficient target energy for visibility. A similar tracking experiment was performed for “unpredictable” target motion. Several changes were observed in the response of the eye-movement control system, and these were related to the effects of luminance upon system parameters and target predictability.

© 1967 Optical Society of America

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References

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  1. D. H. Fender and P. W. Nye, Kybernetik 1, 81 (1961).
    [CrossRef] [PubMed]
  2. D. A. Robinson, J. Physiol. 180, 569 (1965).
  3. L. R. Young, A Sampled Data Model for Eye Tracking Movements, Sc.D. thesis, Massachusetts Institute of Technology (1962).
  4. L. L. Wheeless, R. M. Boynton, and G. H. Cohen, J. Opt. Soc. Am. 56, 956 (1966).
    [CrossRef] [PubMed]
  5. T. N. Cornsweet, J. Opt. Soc. Am. 46, 987 (1956).
    [CrossRef] [PubMed]
  6. G. Van den Brink, Retinal Summation and the Visibility of Moving Objects (Natl. Council for Applied Science Research, Netherlands, 1958).

1966 (1)

1965 (1)

D. A. Robinson, J. Physiol. 180, 569 (1965).

1961 (1)

D. H. Fender and P. W. Nye, Kybernetik 1, 81 (1961).
[CrossRef] [PubMed]

1956 (1)

Boynton, R. M.

Cohen, G. H.

Cornsweet, T. N.

Fender, D. H.

D. H. Fender and P. W. Nye, Kybernetik 1, 81 (1961).
[CrossRef] [PubMed]

Nye, P. W.

D. H. Fender and P. W. Nye, Kybernetik 1, 81 (1961).
[CrossRef] [PubMed]

Robinson, D. A.

D. A. Robinson, J. Physiol. 180, 569 (1965).

Van den Brink, G.

G. Van den Brink, Retinal Summation and the Visibility of Moving Objects (Natl. Council for Applied Science Research, Netherlands, 1958).

Wheeless, L. L.

Young, L. R.

L. R. Young, A Sampled Data Model for Eye Tracking Movements, Sc.D. thesis, Massachusetts Institute of Technology (1962).

J. Opt. Soc. Am. (2)

J. Physiol. (1)

D. A. Robinson, J. Physiol. 180, 569 (1965).

Kybernetik (1)

D. H. Fender and P. W. Nye, Kybernetik 1, 81 (1961).
[CrossRef] [PubMed]

Other (2)

L. R. Young, A Sampled Data Model for Eye Tracking Movements, Sc.D. thesis, Massachusetts Institute of Technology (1962).

G. Van den Brink, Retinal Summation and the Visibility of Moving Objects (Natl. Council for Applied Science Research, Netherlands, 1958).

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Figures (10)

Fig. 1
Fig. 1

Reaction time to ±6° horizontal target steps vs log target luminance. Subject L. W.

Fig. 2
Fig. 2

Histograms of percent occurrence of eye-movement reaction times. (a) Target luminance 1.5 log units below foveal threshold; (b) 1.0 log units below; (c) at foveal threshold; (d) 1.0 log units above; (e) 2.0 log units above. Subject L. W. Note that histogram (a) is represented in an abscissa that is shifted to the left with respect to the other four plots.

Fig. 3
Fig. 3

Reaction time to ±6° horizontal target steps vs target luminance (log–log plot). Subject L. W.

Fig. 4
Fig. 4

Average reaction time to ±6° horizontal target steps vs log target luminance. Luminance was varied while contrast was kept constant. Subject L. W.

Fig. 5
Fig. 5

Average foveal dead zone vs luminance, 5 subjects. Vertical bars indicate standard deviation. (Dashed line to 8° dead zone at D=1.5 below foveal threshold is lower limit since dead zones were not measured above 8°.)

Fig. 6
Fig. 6

Gain vs frequency for sinusoidal ±2° horizontal target motion at various target luminances, (high-contrast condition). Subject J. T. ○ target luminance 1.25 log units above foveal threshold, ● is 0.5 log units above foveal threshold, △ is at foveal threshold, ▲ is 0.3 log units below foveal threshold, and □ is 1.0 log units below foveal threshold.

Fig. 7
Fig. 7

Gain vs frequency for sinusoidal ±2° horizontal target motion at various target luminances, (high-contrast condition). Subject T. J. ○ is target luminance 1.25 log units above foveal threshold, ● is 0.3 log units above foveal threshold, and △ is at foveal threshold.

Fig. 8
Fig. 8

Gain vs frequency for sinusoidal ±2° horizontal target motion (low-contrast condition). Luminance varied while contrast was kept constant. Subject J. T. ○ is target luminance 2.0 log units above contrast threshold, ● is 0.5 log units above contrast threshold, and △ is at contrast threshold.

Fig. 9
Fig. 9

Gain vs frequency for sinusoidal ±2° horizontal target motion (low-contrast condition). Luminance varied while contrast was kept constant. Subject T. J. ○ is target luminance 2.0 log units above contrast threshold, ● is 1.0 log units above contrast threshold, and △ is 0.7 log units above contrast threshold.

Fig. 10
Fig. 10

Average gain and phase vs frequency for unpredictable target motion at various target luminances. Subject L. W. ○ is target luminance 1.5 log units above foveal threshold, ● is 0.5 log units above foveal threshold, and △ is at foveal threshold.