Cite as:
Nieves J L, Valero E M, Garcia J A, Romero J, 1999, "Do chromatic sensitivity thresholds reveal red - green dominance in grating-detection tasks?" Perception 28 ECVP Abstract Supplement

Do chromatic sensitivity thresholds reveal red - green dominance in grating-detection tasks?

J L Nieves, E M Valero, J A Garcia, J Romero

We have tested the influence of colour vision mechanisms in chromatic-grating detection thresholds. The stimuli were isoluminant red - green (r/g) or blue - yellow (b/y) sine-wave gratings generated on a CRT colour monitor. Chromatic contrast values were selected along the r/g axis (deutan line) or y/b axis (tritan line) according to Boynton's model; in addition, two intermediate axes were selected by adding the same r/g and y/b contrast values. Along each axis, we measured the threshold contrast for sixteen spatial frequencies from 1.0 to 4.0 cycles deg^-1. Each threshold was the mean of two measurements obtained with a three-interleaved 2AFC staircase procedure. The test stimulus appeared in one of two time intervals and the other interval was blank. On one hand, the results showed a significant increase of b/y sensitivity for both intermediate axes. This apparently indicates a strong dominance of the r/g mechanism over this range of spatial conditions. On the other hand, the results derived from r/g sensitivity were also in agreement with the aforementioned r/g dominance. For one of the observers, this dominance seemed to be so strong that the addition of some amount of b/y contrast to the r/g contrast did not modify the r/g sensitivity threshold.

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