A contrast paradox in stereopsis, motion detection, and vernier acuity

Stereoacuity improves with increasing contrast, unless the increase is mono cular. In this case performance paradoxically suffers. This study examined whether this contrast paradox occurs for two other classes of visual judgme nt: two-frame motion and vernier acuity. We constructed three homologous ta sks in which the two components of a gabor stimulus (stereo half-images, mo tion frames, vernier components) were either both high contrast, both low c ontrast, or mismatched. The contrast paradox was evident in all three tasks and showed a similar spatial frequency dependence. We suggest the contrast paradox results from the combination of mismatched signals by a single fil ter. (C) 2000 Elsevier Science Ltd. All rights reserved.