Abstract
Simple reaction times to a visual stimulus include visual response time as well as cognitive and motor response umes. To isolate visual response =e and to linut the influence of the cognitive and motor components, a novel psychophysical technique was developecl Two identical targets were flashed, one to each eye of a human subject, against different background luminances and at different times. When the subject perceived the two targets as Sashing simultaneously, the diSerence in presentation times was taken as the measure of the rehtive visual reaction time necessary to process a target at different adaptation levels. Reaction-time differences as measured by this new technique corroborate data from simple reaction times but show much less variability. A small bur measurable drifting of the comparative performance of each eye was observed, perhaps placing an upper limit on the precision of the method. This new technique is an efficient way to determine mesopic luminous efficiency func. tions, among other possible uses.
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