Note on measurement of visual after-image intencity as a function of time.

A simple scaling technique is described, by means of which proportions of an all-or-none type may be transformed to scale values representing the intensity of the perceptual process. This technique is applied to data from experiments on negative visual after-images. The regularity and interpretability of the results support the technique. The fading and returning of the negative after-image is accounted for by a composite function, involving (1) an experimental decline and (2) a sine function with amplitude damping.