Burns, E.M., Ward, W.D. (1978). Categorical perception - Phenomenon or epiphenomenon: Evidence from experiments in the perception of melodic musical intervals. J. Acoust. Soc. Am. 63, 456-468

Categorical perception was investigated in a series of experiments on the perception of melodic musical intervals (sequential frequency ratios). When procedures equivalent to those typically used in speech-perception experi- ments were employed (i.e., determination of identification and discrimination functions for stimuli separated by equal physical increments), musical inter- vals were perceived categorically by trained musicians. When a variable-step-size (adaptive) discrimination procedure was used, evidence of categorical perception (in the form of smaller interval-width DL's for ratios at identi- fication category boundaries than for ratios within categories), although present initially, largely disappeared after subjects had reached asymptotic performance in the adaptive paradigm were not substantially different from those initially obtained. The results of other experiments imply that this dependence of categorical perception on procedure may be related to differences in stimulus uncertainty between the procedures. An experiment on the perception of melodic intervals by musically untrained observers showed no evidence for the existence of "natural" categories for musical intervals.