The establishment of open articulatory postures by deaf and hearing talkers.

Previous researchers have proposed that prelingually deafened talkers do not displace the tongue body to establish vowel steady-state postures and displace the jaw excessively. The purpose of this investigation was to evaluate the opening gesture lingual displacement patterns of three deaf and two hearing adult talkers. Cinefluorography and x-ray microbeam data indicated that the deaf subjects displaced their tongue bodies during the opening gestures. However, their glossal movement trajectories were qualitatively dissimilar to those of the hearing subjects. Whereas the hearing subjects moved the tongue differently for different vowel contexts, the deaf subjects had similar trajectories for all contexts. The common trajectories suggest that some deaf talkers contract their tongue muscles such that the tongue body moves similarly for all vowels. The deaf subjects also appeared to have a less flexible tongue body during speech production than the hearing subjects. Means for quantifying and comparing the lingual behaviors of deaf and hearing talkers are considered.