Mesopic visual efficiency II: reaction time experiments

Reaction times are recorded to chromatic, mesopic stimuli to investigate mesopic reaction time spectral sensitivity. Measurements are made using three laboratory setups and a driving simulator. The chromatic stimuli have spectral distributions that range from quasi-monochromatic to broadband. Reaction time spectral sensitivity for small (0.29°) foveal stimuli changes little with luminance and is described adequately by V (λ). Reaction time spectral sensitivity for peripheral stimuli exhibits a Purkinje shift, and approaches V ' (λ) at 0.01 cd m -2 . In the periphery, the results for medium-sized stimuli (2°) reflect the activity of colour-opponent neurons in addition to rod and cone-based achromatic activity, resulting in three-peaked spectral sensitivity functions.