Reaction-Time Measurements: Their Use and Limitations in Diagnosis

From the early stages of modern experimental psychology-reaction-time experiments have been used in the endeavor to study different psychological processes such as the effect of distracting stimuli on attention, the influence of drugs and alcohol, the influence of the reactor's "attitude", etc. Usually the total number of reactions made by any one subject under one experimental condition did not exceed two hundred; many conclusions drawn from these small samples are not warrantable. The conclusions based on the means of those performances and their dispersion constants would probably have been different had larger samples been taken; but even then, at some specific stage in procedure, the individuals might differ from each other so greatly as to render the reaction-time test useless as a delicate means of diagnosing individual differences. The present experiment was aimed at finding out how widely the individuals vary at different times in their manner of making choice-reactions; how reliable these differences are; and what uses and limitations the choice-reaction test may have in detecting obscure physiological and psychological changes in the human organism.