Abstract

We explored the human observer's ability to discriminate changes in the spatial frequency of Gaussian-truncated sinewave gratings before and after adaptation to high-contrast gratings. The Weber fraction for spatial-frequency discrimination (f/f) was measured for one reference frequency (5 c/deg) as a function of contrast (0.020.32) at a photopic (270 cd/m²) luminance level. Thresholds were estimated before and after adaptation by means of a maximum-likelihood procedure (the BestPEST). Adaptation was for 200 s, with 15 s readaptation after each trial. As was found in earlier studies, f/f decreases monotonically with increasing contrast and approaches an asymptote at contrast levels of 0.030.05 in the unadapted state. After adaptation to a 5 c/deg, high contrast (0.7), counterphase flickered (5 Hz) grating, the function relating f/f to log-contrast shifts to higher contrasts, but the shape of the function and the asymptotic value of f/f do not change. Adaptation to gratings of other spatial frequencies produces smaller shifts. These findings are in line with recent results by Sclar et al.¹ on the effects of adaptation on V1 cells in the macaque.

© 1990 Optical Society of America