A FAST PROCEDURE FOR STUDYING CONDITIONAL ACCURACY FUNCTIONS

This paper describes a procedure for obtaining conditional accuracy fu nctions (CAFs) from naive observers and a restricted number of trials. The method permits the experimenter to counter the subjects' tendency to favor accuracy in tasks in which stimulus discrimination is easy. Each time a block of 12 trials contains less than three errors, observ ers are instructed, by means of a speed-up signal, to respond faster. The subject is continuously informed about her/his effective reaction time. The data show that the desired speed-accuracy tradeoff was obtai ned within each of the 7 observers. The mean percent error was around 25%.