REACTION-TIMES REVEAL THE CONTRIBUTION OF THE DIFFERENT RECEPTOR COMPONENTS IN LUMINANCE PERCEPTION

Pieron (1914, 1920, 1952) demonstrated that simple reaction time decay s as a hyperbolic function of luminance. Similarities between cell lat encies and reaction time (RT) to luminance suggest that this relations hip may be determined by retinal processes. If the exponent of the Pie ron function is specific to a given sensory modality, as assumed by so me authors (e.g., Bonnet, 1992a, 1992b; Norwich, 1987), it should refl ect receptor activities. Consequently, functions with different expone nts should fit data for different luminance ranges. In a contrast-disc rimination experiment, we investigated this question with a large rang e of luminance levels in a two-alternative spatial forced-choice task. The results of the experiment show that three functions with differen t exponents fit RT to the three luminance ranges (scotopic, mesopic, a nd photopic). The exponent decreases with increasing luminance. The fi ndings indicate that the exponent and the asymptotic latency of the RT function reflect receptor activities of the visual system.