Dynamics of adaptation for vision with a stabilized image

The addition of a uniform increment of light to a high-contrast image that has been stabilized on the retina reveals marked perceptual nonlinearities. When the increment is small, the pattern appears in its original phase (OP), large increments produce an apparent phase reversal (APR), and intermediate increments may yield an apparently blank field or an oscillation of the apparent phase. In the present series of studies the threshold values used to produce a stable OP and APR were determined as a function of adaptation time before the application of the increment. The stabilized target had a luminance profile consisting of the difference of two Gaussians. A model of detection incorporating a multiplicative gain controlled by a filtered version of the stimulus was used to account for the occurrence of the OP and the APR and the transitory phenomena following the uniform increment. It is argued that the midpoint of the transition zone between the OP and APR, corresponding to blanking, enables us to estimate the shape of the step response function of the gain filter independently of the subsequent detection processes.