ON MEASURING PSYCHOMETRIC FUNCTIONS - A COMPARISON OF THE CONSTANT-STIMULUS AND ADAPTIVE UP-DOWN METHODS

Psychometric functions were obtained using the conventional constant-s timulus method and an adaptive up-down method, for both computer-simul ated and human observers. Except when the stimuli are closely placed, psychometric functions obtained with the adaptive method are as accura te as those obtained with the constant-stimulus method. Empirically, t he adaptive method has some potential advantages owing to its ability to automatically concentrate the trials within the dynamic range of th e psychometric function. It needs no pilot measurements for setting th e signals as required by the constant-stimulus method. Furthermore, fo llowing a marked change in the underlying psychometric function, the d istribution of the trials is automatically readjusted. Thus, on the ba sis of empirical considerations, the adaptive method is a better choic e than the constant-stimulus method for measuring psychometric functio ns. (C) 1995 Acoustical Society of America.