Reaction times to chromatic stimuli

The relative contributions of chromatic and achromatic activity to reaction time were investigated under conditions in which spatial and temporal transients were manipulated. Simple reaction times (RT) were obtained to eight photometrically matched (1 cd/m2) wavelengths between 448 and 658 nm. These stimuli were incrementally presented on a spatially coextensive 1.2 degrees white adapting field. RT was wavelength dependent for 5 or 10 cd/m2 steady backgrounds or a 5 Hz 1.2 cd/m2 flickering background. RT varied as a trichromatic saturation-like function (slowest RT at 572 nm). In comparison, RT was wavelength independent when no adapting field was present and when the 1.2 cd/m2 field was flickered at 15 Hz.