ROCs obtained with two signal intensities presented in random order,and a comparison between yes-no and rating ROCs

Two experiments are presented. The first experiment investigated the effect of mixing signals of two different intensities within the same blocks of trials upon receiver operating characteristics (ROCs) obtained with the rating procedure. The ROCs obtained when the signals of differing intensity were mixed in blocks of trials were found to be quite similar to those obtained when only one signal intensity was presented in any given block of trials. In the second experiment ROCs were determined by having subjects adopt different decision criteria on different blocks of trials in a yes-no experiment. The data points obtained in this experiment fell quite close to the ROCs obtained from the same subjects with the rating procedure in the first experiment.