The Impact of Cerebral Palsy on the Intelligibility of Pitch-based Linguistic Contrasts

Abstract

This study investigated the perception of three Cantonese level tones produced by speakers with dysarthria associated with cerebral palsy. Four speakers with dysarthria were selected on the basis of their distinctive patterns of fundamental frequency (F0) values observed in the level tones they produced, which showed errors in either F0 level or, F0 contour, or both. Monosyllabic words which contrasted in tone level were used as stimuli in an identification task. Five expert listeners identified the tones among the six Cantonese contrastive tones. Results showed that the tones produced by the dysarthric speakers were predominantly perceived as level tones; although a majority was perceived as the wrong level tone. The most important finding is that only the level tones produced by dysarthric speakers could be identified as rising or falling contour tones. The frequent perceptual confusion among the level tones, and the perception of contour tones, shows that a disorder in the production of pitch-based linguistic contrasts can have a substantial impact on the communication abilities of individuals with cerebral palsy.