Simple reaction time to chromatic changes along L&M-constant and S-constant cone axes

The present study uses simple reaction time (RT) to examine the temporal re sponse to chromatic changes of the red-green (L-2M) and yellow-blue (S-(L+M )I chromatic opponent channels. The hue-substitution method,vas adopted to negate the luminance channel and generate changes in the chromatic input. T he equiluminant stimuli were distributed along three tritanopic and three r ed-green confusion lines. RTs were measured at equiluminance from three ref erence stimuli with chromatic changes occurring in either the tritan or red -green directions. These reference stimuli also allowed evaluation of the i nfluence of chromatic adaptation level on RT The results show ed that the m ean value of RT, for the cone-input variation either of the L-2M channel (S -constant cone axis) or of the S-(L+M) channel (L&M-constant cone axis), wa s described by a similar law as for luminance variations (Pieron's law). Th en, the sensitivity of the two channels for chromatic changes lr us equaliz ed to study their relative response speed in addition, for both axes, an in crease in the chromatic adaptation level lengthens response delay. (C) 2001 John Wiley & Sons, Inc.