Abstract

Vision seems to be a continuous process even though eye movements occupy a portion of the time spent in reading or inspecting objects in the field of view. This observation has led to the supposition that a “blanking out” of vision occurs with saccadic eye movements. Some workers attribute this effect to the rapid motion of the image on the retina. Others have suggested a central inhibition, possibly related to the physiological mechanisms of attention. The present research compared vision during saccades with vision during fixation by means of three representative psychophysical tasks. Each stimulus pattern was presented to the fovea in the form of an instantaneous flash that was delivered before, during, or after an eye movement. The flash lasted only 20 μsec, so that retinal blur due to movement was reduced to a negligible amount. The time of the stimulus flash was signaled on a continuously moving film on which the eye movements were recorded by a corneal reflection technique. Detection thresholds for dot patterns and recognition thresholds for words were found to be about 0.5 log unit higher during saccades than during steady fixation. Similar differences, though smaller and less consistent, were found in the minimum angles for the resolution of gratings. It is concluded that vision is not “blanked out” during eye movements, but that it is significantly depressed even under conditions that minimize blur due to movement of the retinal image, and that assure foveal stimulation.

© 1962 Optical Society of America

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References

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  1. B. Erdmann and R. Dodge, Psychologische Untersuchungen über das Lesen auf Experimenteller Grundlage (Max Niemeyer, Halle a. S., 1898), pp. 69–76.
  2. R. Dodge and T. S. Cline, Psychol. Rev. 8, 145 (1901).
    [CrossRef]
  3. R. Dodge, Psychol. Rev. 7, 454 (1900).
    [CrossRef]
  4. R. Dodge, Psychol. Bull. 2, 193 (1905).
    [CrossRef]
  5. R. S. Woodworth, Psychol. Bull. 3, 68 (1906).
  6. See reference 5, p. 68ff.
  7. E. B. Holt, Harvard Psychol. Stud. I, 3 (1903).
  8. S. Exner, Z. Psychol. I, 47 (1890).
  9. G. H. Bell and J. B. deV. Wier, Trans. Ophthalmol. Soc. U. K. LXVII, 221 (1947).
  10. R. W. Ditchburn, Optica Acta I, 171 (1954–1955).
  11. D. B. Lindsley, EEG Clin. Neurophysiol. 4, 443 (1952).
    [CrossRef]
  12. R. K. Meister, “Hypothesis concerning the function of the occipital alpha rhythm in vision with special reference to the perception of movement,” unpublished doctoral dissertation (University of Chicago, 1951).
  13. See reference 11, p. 448ff.
  14. H. Cason, J. Exptl. Psychol. 16, 295 (1933).
    [CrossRef]
  15. The results obtained by stimulating the eye when it was moving to the right and when it was moving to the left have been plotted separately, since vision was always slightly better when the flash arrived during movements to the left. For the present three subjects this effect was independent of handedness and of the relative velocities of saccades in the two directions.
  16. S. Siegel, Nonparametric Statistics (McGraw-Hill Book Company, Inc., New York, 1956), Chap. 9, p. 229.
  17. These figures represent the maximum amount of smear which could be expected, based on the mean peak velocity of the eye movements from the subject whose saccades were most rapid, and on a figure for the flash duration which includes the entire time at which the flash exceeded one-third of its peak intensity. For near-threshold flashes, it is doubtful that all of this light was effective.
  18. The ellipse of light which struck the eye had to be exactly centered on the cornea in order to be reflected accurately to the photomultiplier tube when the subject looked straight ahead. Since the light fell on the cornea at a 20° angle, however, only a portion of it entered the pupil, at the left side. When the 20° angle of incidence is considered along with the location of the fixation marks in each experimental condition (see Fig. 4) it may be seen that when the subject looked at the left-hand fixation mark in the FIX R 2 condition, the angle at which the focused light struck the eye was increased to 26°, and a considerable portion of this light could enter the eye through the pupil. When the subject looked at the right-hand fixation mark in the FIX L 2 condition, this angle decreased to 14°, and very little light entered the pupil. The angles of incidence and corresponding amounts of light entering the pupil were intermediate between these limits in the other experimental conditions.

1952 (1)

D. B. Lindsley, EEG Clin. Neurophysiol. 4, 443 (1952).
[CrossRef]

1947 (1)

G. H. Bell and J. B. deV. Wier, Trans. Ophthalmol. Soc. U. K. LXVII, 221 (1947).

1933 (1)

H. Cason, J. Exptl. Psychol. 16, 295 (1933).
[CrossRef]

1906 (1)

R. S. Woodworth, Psychol. Bull. 3, 68 (1906).

1905 (1)

R. Dodge, Psychol. Bull. 2, 193 (1905).
[CrossRef]

1903 (1)

E. B. Holt, Harvard Psychol. Stud. I, 3 (1903).

1901 (1)

R. Dodge and T. S. Cline, Psychol. Rev. 8, 145 (1901).
[CrossRef]

1900 (1)

R. Dodge, Psychol. Rev. 7, 454 (1900).
[CrossRef]

1890 (1)

S. Exner, Z. Psychol. I, 47 (1890).

Bell, G. H.

G. H. Bell and J. B. deV. Wier, Trans. Ophthalmol. Soc. U. K. LXVII, 221 (1947).

Cason, H.

H. Cason, J. Exptl. Psychol. 16, 295 (1933).
[CrossRef]

Cline, T. S.

R. Dodge and T. S. Cline, Psychol. Rev. 8, 145 (1901).
[CrossRef]

Ditchburn, R. W.

R. W. Ditchburn, Optica Acta I, 171 (1954–1955).

Dodge, R.

R. Dodge, Psychol. Bull. 2, 193 (1905).
[CrossRef]

R. Dodge and T. S. Cline, Psychol. Rev. 8, 145 (1901).
[CrossRef]

R. Dodge, Psychol. Rev. 7, 454 (1900).
[CrossRef]

B. Erdmann and R. Dodge, Psychologische Untersuchungen über das Lesen auf Experimenteller Grundlage (Max Niemeyer, Halle a. S., 1898), pp. 69–76.

Erdmann, B.

B. Erdmann and R. Dodge, Psychologische Untersuchungen über das Lesen auf Experimenteller Grundlage (Max Niemeyer, Halle a. S., 1898), pp. 69–76.

Exner, S.

S. Exner, Z. Psychol. I, 47 (1890).

Holt, E. B.

E. B. Holt, Harvard Psychol. Stud. I, 3 (1903).

Lindsley, D. B.

D. B. Lindsley, EEG Clin. Neurophysiol. 4, 443 (1952).
[CrossRef]

Meister, R. K.

R. K. Meister, “Hypothesis concerning the function of the occipital alpha rhythm in vision with special reference to the perception of movement,” unpublished doctoral dissertation (University of Chicago, 1951).

Siegel, S.

S. Siegel, Nonparametric Statistics (McGraw-Hill Book Company, Inc., New York, 1956), Chap. 9, p. 229.

Wier, J. B. deV.

G. H. Bell and J. B. deV. Wier, Trans. Ophthalmol. Soc. U. K. LXVII, 221 (1947).

Woodworth, R. S.

R. S. Woodworth, Psychol. Bull. 3, 68 (1906).

EEG Clin. Neurophysiol. (1)

D. B. Lindsley, EEG Clin. Neurophysiol. 4, 443 (1952).
[CrossRef]

Harvard Psychol. Stud. (1)

E. B. Holt, Harvard Psychol. Stud. I, 3 (1903).

J. Exptl. Psychol. (1)

H. Cason, J. Exptl. Psychol. 16, 295 (1933).
[CrossRef]

Optica Acta (1)

R. W. Ditchburn, Optica Acta I, 171 (1954–1955).

Psychol. Bull. (2)

R. Dodge, Psychol. Bull. 2, 193 (1905).
[CrossRef]

R. S. Woodworth, Psychol. Bull. 3, 68 (1906).

Psychol. Rev. (2)

R. Dodge and T. S. Cline, Psychol. Rev. 8, 145 (1901).
[CrossRef]

R. Dodge, Psychol. Rev. 7, 454 (1900).
[CrossRef]

Trans. Ophthalmol. Soc. U. K. (1)

G. H. Bell and J. B. deV. Wier, Trans. Ophthalmol. Soc. U. K. LXVII, 221 (1947).

Z. Psychol. (1)

S. Exner, Z. Psychol. I, 47 (1890).

Other (8)

B. Erdmann and R. Dodge, Psychologische Untersuchungen über das Lesen auf Experimenteller Grundlage (Max Niemeyer, Halle a. S., 1898), pp. 69–76.

See reference 5, p. 68ff.

R. K. Meister, “Hypothesis concerning the function of the occipital alpha rhythm in vision with special reference to the perception of movement,” unpublished doctoral dissertation (University of Chicago, 1951).

See reference 11, p. 448ff.

The results obtained by stimulating the eye when it was moving to the right and when it was moving to the left have been plotted separately, since vision was always slightly better when the flash arrived during movements to the left. For the present three subjects this effect was independent of handedness and of the relative velocities of saccades in the two directions.

S. Siegel, Nonparametric Statistics (McGraw-Hill Book Company, Inc., New York, 1956), Chap. 9, p. 229.

These figures represent the maximum amount of smear which could be expected, based on the mean peak velocity of the eye movements from the subject whose saccades were most rapid, and on a figure for the flash duration which includes the entire time at which the flash exceeded one-third of its peak intensity. For near-threshold flashes, it is doubtful that all of this light was effective.

The ellipse of light which struck the eye had to be exactly centered on the cornea in order to be reflected accurately to the photomultiplier tube when the subject looked straight ahead. Since the light fell on the cornea at a 20° angle, however, only a portion of it entered the pupil, at the left side. When the 20° angle of incidence is considered along with the location of the fixation marks in each experimental condition (see Fig. 4) it may be seen that when the subject looked at the left-hand fixation mark in the FIX R 2 condition, the angle at which the focused light struck the eye was increased to 26°, and a considerable portion of this light could enter the eye through the pupil. When the subject looked at the right-hand fixation mark in the FIX L 2 condition, this angle decreased to 14°, and very little light entered the pupil. The angles of incidence and corresponding amounts of light entering the pupil were intermediate between these limits in the other experimental conditions.

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Figures (7)

Fig. 1
Fig. 1

Schematic diagram of optical system, not to scale. Path A indicates the subjects’ view of the stimulus (R) and fixation (T) fields. Path B shows the arrangement of the light used to provide the corneal reflection for recording eye movements on moving film (F) and for triggering the stimulus flash by means of the photomultiplier tube (PM). Path C shows the optical system used to record the stimulus flash on the film. For further explanation see text.

Fig. 2
Fig. 2

Wiring diagram showing how light falling on the photo-multiplier tube from the corneal reflection was used to trigger the stimulus strobe flash.

Fig. 3
Fig. 3

Examples of photographic records showing the relation of a stimulus flash to each eye movement in the various experimental conditions. The 35-mm film moved at 25 cm per sec.

Fig. 4
Fig. 4

Schematic diagram of fixation marks and a sample stimulus pattern, showing how the fixation marks were adjusted to provide foveal stimulation in all experimental conditions. Not to scale.

Fig. 5
Fig. 5

Percentage of light flashes detected, as a function of the log relative luminance of the flash for each subject in each experimental condition.

Fig. 6
Fig. 6

Percentage of flashes in which grating test objects were resolved, as a function of lines per inch of the grating, for each subject in each experimental condition. A forced-choice method of report was used; thus the curves begin at the 50% chance level on the ordinate.

Fig. 7
Fig. 7

Percentage of exposures in which words were recognized, as a function of the log relative luminance of the flash for each subject in each experimental condition.