Disruption of categorical processing in music

Abstract

Musicians judged 13 tonal intervals under magnitude estimation instructions. The intervals were spaced in 20-cent steps and covered a range of three semitone categories. In experiment I, the subjects were naive with respect to the exact nature of the stimulus set, and under these conditions, evidence for categorical perception was obtained. The psychometric functions were well predicted by these subjects identification of the same stimuli. Stimuli in different categories were judged as perceptually distinct, but the judgment of intonation within a category was poor. That is, these subjects were unable to distinguish among sharp, in-tune, and flat stimuli with the same interval name. In Experiment II, subjects were given specific information concerning the nature of the stimuli. Their judgment of within-category differences failed to improve, and their assignment of the stimuli to the three interval categories became more variable. It appears that musicians are poor at judging within-category differences in intonation, and that attempting to do so disrupts the processing of categorical information.