On the Identification and Discrimination of Very Brief Vowels

Abstract

The distinction between categorical and continuous modes of speech perception has played an important role in theoretical accounts of the speech perception process. Certain classes of speech sounds, such as stop consonants, are usually perceived in a categorical or phonetic mode. Listeners can discriminate two sounds only to the extent that they have identified these stimuli as different phonetic segments. Discrimination functions are not monotonic with changes in the physical scale but show marked discontinuities at points along the continuum that are correlated with changes in identification. Recently, several findings have suggested that vowels, which are usually perceived in a continuous mode, may also be perceived categorically, although this outcome may be dependent upon various experimental manipulations. This paper reports the results of a series of experiments which examined the identification and discrimination of brief 50-msec vowels and longer 300-msec vowels under a variety of experimental conditions. The type of discrimination test, the duration of the stimuli, the range and spacing of the stimuli, and the context of the stimuli all contribute in various ways to the observed differences in shape and relative level of discrimination in vowel perception. Although under some circumstances vowels may be perceived in a categorical-like mode, quantitative differences still exist in the perception of stop consonants and vowels.