An unusual kind of contrast adaptation: shifting a contrast comparison level.
We have found an unusual kind of contrast adaptation in human pattern vision that seems fundamentally different from previously reported effects. As the observer adapts to different levels of contrast, the visibility of some contrast-defined (second-order) patterns dramatically increases and that of others dramatically decreases. Oddly, visibility is poor for patterns containing contrasts both above and below the recent average contrast. To explain these effects, we hypothesize a new kind of process acting in concert with a known contrast-gain control of the normalization type. The new process compares current contrast to an adaptable comparison level; this level reflects the recent average contrast. Such a process existing at an early stage of visual processing is likely to have widespread effects at higher stages.
Department of Psychology, Columbia University, New York, NY 10027, USA. sabina@psych.columbia.edu
S Sabina
SS
Wolfson
Norma
N
Graham
D000223:Adaptation, Psychological / Q000502:physiology*; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008960:Models, Psychological; D010364:Pattern Recognition, Visual / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology