Categorical Perception of Musical Intervals

A body of evidence indicates that certain speech units are perceived in a special mode called “categorical perception,” the characteristics of which are (1) the existence of well-defined identification functions and (2) the ability to predict precisely the discrimination functions from the identification functions, based on the assumption that the subjects can discriminate two stimuli no better than they can differentially identify them. Categorical perception is usually assumed to be a unique property of speech and is part of the evidence supporting the idea that “speech is special.” A study of the perception of musical intervals by experienced musicians was performed using the procedures associated with categorical perception experiments; that is, identification and discrimination functions were obtained for points equally spaced along a physical continuum, in this case equal distances in cents along the logarithmic frequency scale defining musical pitch. The results show that the musicians exhibit categorical perception, some to a degree approaching that shown in the perception of stop consonants. The relation of these results to those of the relevant speech perception experiments and of other experiments in musical perception is discussed.