The Eyes Have It

The Measurement of Sensation: A Critique of Perceptual Psychophysics

by C. Wade Savage
University of California, 590 pp., $15.00

Selective History of Theories of Visual Perception: 1650-1950

by Nicholas Pastore
Oxford, 464 pp., $10.00

The Intelligent Eye

by R.L. Gregory
McGraw-Hill, 191 pp., $7.95

Eye and Brain: The Psychology of Seeing

by R.L. Gregory
McGraw-Hill, 303 pp., $2.45 (paper)

The World Through Blunted Sight

by Patrick Trevor-Roper
Bobbs-Merrill, 191 pp., $12.50

If any part of psychology has enjoyed undisputed respectability it is the ritual of getting people to lift two small weights one after the other and say whether the second is heavier or lighter than the first. Or they can watch lights or listen to tones and make a judgment of relative brightness or loudness. Endless man-hours have been spent in these devoted exercises, all supposedly establishing numerical relations between physical dimensions like the amplitude of sound waves and sensory or psychological dimensions like loudness. As an impatient undergraduate putting in my stint on the treadmill, I comforted myself with the belief that this activity was a vestige, a hangover from the nineteenth century, soon to be displaced by real psychology. Today it still flourishes, claiming notable advances in method, statistical elaboration, and conceptual sophistication.

And now Mr. Savage, a philosopher at UCLA, denies that psychophysics measures psychological dimensions at all. Without questioning the value of what has been done he argues that the nature of the undertaking has been misconceived; his title is an irony since his theme is that what has been measured is neither sensation, as Fechner supposed in 1860, nor the psychological magnitudes that S. S. Stevens of Harvard has claimed to measure a hundred years later by different methods from Fechner’s.

It may be surprising that such an apparently arid topic still gains attention, but it forms part, perhaps the basis, of the interest in perception, and especially visual perception, which is very much alive at the present time among artists as well as philosophers and psychologists. Of course psychophysical measurement serves a diversity of purposes. Like any other academic pursuit it provides a medium in which reputations and careers are made. It produces, as spin-off, some refinements of practical techniques for assessing individuals’ sensory equipment, mainly sight and hearing. But eventually its nourishment is drawn from a perennial interest in the processes by which physical events such as light waves or the pull of gravity produce experience or, if we prefer, discriminatory response in a living organism.

Nicholas Pastore provides an extremely useful critical introduction to three centuries of observation and thinking about visual perception, especially the question whether our perception of depth, solidity, and distance has to be learned through touching, grasping, reaching—muscular exploration in general—or comes as an immediate visual datum, as immediate as two-dimensional shape. Associated with this question is the problem of the “constancies,” the fact that we recognize objects as the same even though differences of distance or tilt or illumination produce sharply different retinal images. The view that all these things depend on inference and learning prevailed throughout the greater part of the period Mr. Pastore surveys and has been maintained in one form or another by influential modern psychologists, whether in the conditioning theories of Hull and Hebb or in the “transactionalism” of Ames, whose work comes just at the end of the three centuries.

Ames’s demonstrations are striking and well-known, especially the …

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Letters

Psychophysical Research October 7, 1971