A visual mechanism tuned to black.
Chubb et al. [Journal of the Optical Society of America A 11 (1994) 2350] investigated preattentive discrimination of achromatic textures comprising random mixtures of 17 Weber contrasts ranging linearly from -1 to 1. They showed that only a single mechanism B is used to discriminate between textures whose histograms are equated in mean and in variance. Although they provided a partial characterization of B, their methods did not allow them to measure the sensitivity of B to texture mean and variance. Here, additional measurements are performed to complete the functional characterization of B. The results reveal that B (i) is strongly activated by texture elements of the lowest contrast (near -1), (ii) is slightly activated by texture elements of contrast -0.875, and (iii) barely distinguishes the 15 contrasts ranging from -0.75 all the way up to 1. To reflect the sharpness of its tuning to very dark, sparse elements in a predominantly bright scene, we call B the blackshot mechanism.
Department of Cognitive Sciences & Institute for Mathematical Behavioral Sciences, University of California at Irvine, USA.
Charles
C
Chubb
Michael S
MS
Landy
John
J
Econopouly
D015350:Contrast Sensitivity / Q000502:physiology; D004192:Discrimination, Psychological / Q000502:physiology*; D006801:Humans; D008297:Male; D008960:Models, Psychological; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011594:Psychometrics; D011601:Psychophysics