Purchase this article with an account.
K. Knoblauch, R. Bouet; Integration over the Equiluminant Plane during Chromatic Discrimination . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3192.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Two experiments evaluated how observers integrate information in color space during chromatic discrimination. First, chromatic discrimination thresholds were measured along cardinal and intermediate directions in the presence of sectored noise (SN) centered on the signal direction. Second, classification images (CI) (Ahumada, 1996) were obtained for discrimination of signals along the same directions in the presence of noise distributed independently along the signal and orthogonal directions. Methods: In both tasks, the observer was required to detect a gaussian temporal pulse (σ=160 ms) modulated over a gaussian region of the screen (σ=2.5 deg). In the SN task, threshold vs noise (tvn) curves were measured along the (L-M), -S and an intermediate axis, estimated as midway between the former two in threshold units. Three sector half-widths were tested (0, 30, 60 deg). In the CI task, the same signal axes were tested but the uniform masking noise was the sum of independent samples along the signal and orthogonal axes. CI's were calculated for both axes based on the observer's classification of signal and noise trials. Results: For the SN task, the tvn data were best described by a single curve independently of sector width of the noise for all signal directions. Along cardinal directions, the CI's for the noise axial with the signal direction followed the signal and were unmodulated about zero along the orthogonal direction. For intermediate directions, this was found to be true also except for an unmodulated bias away from zero along the orthogonal direction. Conclusions: The results demonstrate linear mechanisms intermediate to the cardinal directions. The classification image experiments, however, indicate a slight influence of the orthogonal direction on the observer's judgments, but not in a manner that follows the signal modulation.
This PDF is available to Subscribers Only