LUMINANCE, NOT BRIGHTNESS, DETERMINES TEMPORAL BRIGHTNESS ENHANCEMENT WITH CHROMATIC STIMULI

Brightness-duration relations for chromatic stimuli were studied using three pulse-to-background luminance relations: chromatic equal-luminance pulses (3. 2 cd/m**2) were presented as increments of 0. 3 or 1. 0 log units above a lower luminance achromatic background, or were presented in hue substitution, equated in luminance to the achromatic background, so that no spatio-temporal luminance transients occurred during stimulus presentation. Incremental pulses produced temporal brightness enhancement (the Broca-Sulzer phenomenon), but hue substitution pulses did not. Temporal brightness enhancement thus depends upon the occurrence of luminance transients and cannot be produced by pulsed-to-background brightness differences associated solely with chromaticity differences.