Reaction time and accuracy

The fraction of errors in a binary reaction experiment is found to depend upon reaction time. This effect, already apparent in a free reaction time experiment, is corroborated by using the method of forced reaction time. In this method the subject is instructed to react in coincidence with an additional command signal. The binary stimulus then serves as an information signal only. The dependence of the fraction of errors upon reaction time seems to rule out any theory based upon the assumption that the subject reacts if and when he has obtained a fixed certainty regarding the quality of the stimulus.