Perceptual assimilation in context and isolation

Abstract

A study was conducted to examine the effects of sentence context and speaking rate in the perceptual assimilation of non-native speech sounds. Native speakers of American English were presented with two voicing contrasts, [k]-[g] and [t\/sh]-[d\/yog], produced by two Hindi speakers. They appeared word-initially before [a] and within a short sentence frame. These sentences were produced at three speaking rates (slow, normal, and fast). Listeners were administered a categorial AXB discrimination test and a forced-choice identification test. The results were compared to those collected in a previous study that employed the same contrasts appearing in isolated words and produced by the same talkers. The results showed that the discrimination of these speech sounds in a sentence frame was significantly poorer relative to the isolation context. Moreover, the modal native consonant used to classify the Hindi stops varied depending upon the sentence context variable: in isolation, more discriminable uncategorizable assimilation types were elicited, while in a sentence frame, Hindi contrasts tended to be classified using a single English (voiced) consonant. Speaking rate only showed modest effects on proportion of responses represented by the modal native consonants. These results highlight the sensitivity of perceptual patterns elicited in the laboratory to experimental variables.