Abstract

When filters of unequal optical density are placed in front of the two eyes, a target which is actually oscillating in a frontoparallel plane appears nearer than it really is for one direction of stroke and farther than it really is for the return stroke (Pulfrich stereophenomenon). Measurements of the near and far displacements of an oscillating black vertical rod are obtained as functions of (a) target thickness, (b) target velocity, and (c) condition of unequal binocular retinal illuminance.

The experimental data show that variation in target thickness has no effect on the magnitude of the apparent near and far displacements. Variations in target velocity and in condition of unequal binocular retinal illuminance produce characteristic effects which are shown to be in good quantitative agreement with geometrical predictions based on the theory of the Pulfrich stereophenomenon. Discrepancies in the magnitude of the displacements at low target velocities are noted and discussed.

© 1960 Optical Society of America

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References

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  1. C. Pulfrich, Naturwissenschaften 10, 553–564, 569–574, 596–601, 714–722, 735–743, and 751–761 (1922).
    [Crossref]
  2. A. Lit, Am. J. Psychol. 62, 159–181 (1949).
    [Crossref] [PubMed]
  3. A. Lit and A. Hyman, Am. J. Optom. 28, 564–580 (1951).
    [Crossref]
  4. A. Lit, J. Exptl. Psychol. (to be published).
  5. E. Engelking and F. Poos, Arch. Ophthalmol. 114, 340–379 (1924).
  6. F. W. Fröhlich, Z. Sinnesphysiol. 55, 1–46 (1923).

1951 (1)

A. Lit and A. Hyman, Am. J. Optom. 28, 564–580 (1951).
[Crossref]

1949 (1)

A. Lit, Am. J. Psychol. 62, 159–181 (1949).
[Crossref] [PubMed]

1924 (1)

E. Engelking and F. Poos, Arch. Ophthalmol. 114, 340–379 (1924).

1923 (1)

F. W. Fröhlich, Z. Sinnesphysiol. 55, 1–46 (1923).

1922 (1)

C. Pulfrich, Naturwissenschaften 10, 553–564, 569–574, 596–601, 714–722, 735–743, and 751–761 (1922).
[Crossref]

Engelking, E.

E. Engelking and F. Poos, Arch. Ophthalmol. 114, 340–379 (1924).

Fröhlich, F. W.

F. W. Fröhlich, Z. Sinnesphysiol. 55, 1–46 (1923).

Hyman, A.

A. Lit and A. Hyman, Am. J. Optom. 28, 564–580 (1951).
[Crossref]

Lit, A.

A. Lit and A. Hyman, Am. J. Optom. 28, 564–580 (1951).
[Crossref]

A. Lit, Am. J. Psychol. 62, 159–181 (1949).
[Crossref] [PubMed]

A. Lit, J. Exptl. Psychol. (to be published).

Poos, F.

E. Engelking and F. Poos, Arch. Ophthalmol. 114, 340–379 (1924).

Pulfrich, C.

C. Pulfrich, Naturwissenschaften 10, 553–564, 569–574, 596–601, 714–722, 735–743, and 751–761 (1922).
[Crossref]

Am. J. Optom. (1)

A. Lit and A. Hyman, Am. J. Optom. 28, 564–580 (1951).
[Crossref]

Am. J. Psychol. (1)

A. Lit, Am. J. Psychol. 62, 159–181 (1949).
[Crossref] [PubMed]

Arch. Ophthalmol. (1)

E. Engelking and F. Poos, Arch. Ophthalmol. 114, 340–379 (1924).

Naturwissenschaften (1)

C. Pulfrich, Naturwissenschaften 10, 553–564, 569–574, 596–601, 714–722, 735–743, and 751–761 (1922).
[Crossref]

Z. Sinnesphysiol. (1)

F. W. Fröhlich, Z. Sinnesphysiol. 55, 1–46 (1923).

Other (1)

A. Lit, J. Exptl. Psychol. (to be published).

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Figures (5)

Fig. 1
Fig. 1

Geometrical representation of the Pulfrich stereophenomenon indicating the stereoscopic space-image in the horizontal plane of fixation.

Fig. 2
Fig. 2

Schematic representation of the apparatus and observer’s view of stimulus targets. (a) The observer is seated in a dark room (D) and binocularly observes the fixation target (FT) located in the lower visual field and the oscillating target (OT) located in the upper visual field through a pair of artificial pupils (E). Movement of the oscillating target in a frontoparallel plane 100 cm from the observer’s eyes can be varied over a wide range of constant linear velocities. The fixation target in the observer’s vertical median plane can be moved either toward or away from his eyes by means of a pulley-wheel (W) located in the dark room. Background illumination is provided by a lightbox (L). The retinal illuminance of each eye is controlled by neutral density filters placed in the pair of filter boxes (F). Horizontal (H) and vertical (V) screens provide a constant rectangular field of view. (b) The upper rod is the oscillating target; the lower rod is the fixation target. (From Lit and Hyman.3)

Fig. 3
Fig. 3

Average latency difference as a function of target velocity. The number accompanying each curve represents the magnitude of the difference in binocular retinal illuminance, log (ER/EL), where the retinal illuminance of the left eye, logEL, is kept constant at 2.06 log trolands.

Fig. 4
Fig. 4

Average latency difference as a function of differences in binocular retinal illuminance. The number accompanying each curve represents the prevailing target velocity in deg/sec.

Fig. 5
Fig. 5

The hypothesized absolute visual latent period (t) as a function of retinal illuminance (logE). The curve represents an assumed relationship proposed to account for the experimental fact that, for the given constant retinal illuminance of the left eye (logEL), latency difference (Δt) increases progressively as the difference in binocular retinal illuminance [log(ER/EL) is increased.

Tables (3)

Tables Icon

Table I Depth displacements obtained under a given condition of unequal binocular retinal illuminance for six target thicknesses (diameters) and eight target velocities. The retinal illuminance of the left eye is 2.06 log trolands and that of the right eye is 3.13 log trolands. CN and CF refer, respectively, to the near and far displacements of a target oscillating at the specified linear velocities in a frontoparallel plane located 100 cm from the observer’s eyes. Each entry for the two observers (F.C. and M.M.) is based on the mean of 12 settings.

Tables Icon

Table II Depth displacements obtained under three conditions of unequal binocular retinal illuminance, log(ER/EL), for two target thicknesses (diam) and eight target velocities. The retinal illuminance of the left eye, logEL, is kept constant at 2.06 log trolands. CN and CF refer, respectively, to the near and far displacements of a target oscillating in a frontoparallel plane located 100 cm from the observer’s eyes. Each entry is based on the mean of 12 settings obtained from observer M.M.

Tables Icon

Table III Average latency difference 〈Δt〉 as a function of target thickness (diam) and target velocity. Each entry represents the average of the near and far latency differences (ΔtN and ΔtF) computed from Eq. (4) for each set of values of the near and far displacements (CN and CF) obtained from observer M.M. The retinal illuminance of the left eye, logEL, is kept constant at 2.06 log trolands. The latency differences are given in msec.

Equations (4)

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X = b C N / ( d - C N )             and             X = b C F / ( d + C F ) ,
t = X / V .
Δ t = 2 X / V .
and             Δ t N = 2 b V · C N d - C N Δ t F = 2 b V · C F d + C F .