The Basis of Psychophysical Judgments

The notion that we learn to judge the intensities of our sensations only by noting their relation to one or another stimulus property is becoming less plausible as new discoveries are made in psychophysics. (1) By direct cross-modality comparisons, great variety has been demonstrated in the operating characteristics of the various sensory channels. (2) Loudness grows as a power function of sound pressure with an exponent different from that which the learning theory predicts. (3) In the visual system, the operating characteristic can be drastically altered by changing the state of adaptation of the sense organ and by setting up inhibitory processes under simultaneous contrast.