The Pulfrich Effect: Alpern (1968)

Alpern, M. A Note on Visual Latency. Psychological Review, 1968, 75, 260 - 264.
Collage based on Drude 1902, p. 305:  Formula for the intensity of Newton's rings

Note: Permission to reproduce this paper has been withheld by the publisher,
The American Psychological Association.


by John Michael Williams, 1998. Placed in Public Domain.

A theoretical treatment of the Pulfrich effect is developed for combining data on the assumption that the time constant at corresponding depths in any human visual system will be the same for both eyes.

A superthreshold model of latency based on the Hodgkin-Huxley equations is derived. Setting a solution of the homogeneous system equal to the input retinal illuminance I yields a time constant tau such that,

tau = (tau0 * w) / vn

for vn the output of the n-th serial stage of visual processing, tau0 a dark-current time constant, and w a scaling constant.

This approach leads to a power-function formula for the Pulfrich latency,

delta-T = T0 - K * I -1/(n+1),

in which K is an arbitrary scaling constant, and T0 represents an offset latency associated with the lower-I Pulfrich target.
Lit's classic 1949 data then are fit almost perfectly by this formula with n = 4, K = 78, and T0 = 71.9.

One conclusion is that the system yielding the Pulfrich latencies must be equivalent temporally to a system with about four Hodgkin-Huxley-like stages.

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The Pulfrich Effect, SIU-C. Last updated 2000-07-23