Long-distance coarticulation: A production and perception study of English and American Sign Language

This project investigates the production and perception of long-distance coarticulation, defined here as the articulatory influence of one phonetic element (e.g. consonant or vowel) on another across more than one intervening element. Part I explores anticipatory vowel-to-vowel (VV) coarticulation in English; Part II deals with anticipatory location-to-location (LL) effects in American Sign Language (ASL). Long-distance effects were observed in both speech and sign production, sometimes across several intervening elements. Even such long-distance effects were sometimes found to be perceptible.;For the spoken-language study, sentences were created in which multiple consecutive schwas (target vowels) were followed by various context vowels. Thirty-eight English speakers were recorded as they repeated each sentence six times, and statistical tests were performed to determine the extent to which target vowel formant frequencies were influenced differently by the context vowels. For some speakers, significant effects of one vowel on another were found across as many as five intervening segments. The perception study used behavioral methods and found that even the longest-distance effects were perceptible to some listeners; nearer-distance effects were detected by all participants. Subjects' coarticulatory production tendency was not correlated with either speaking rate or perceptual sensitivity.;Seventeen perception-study subjects also provided EEG data for an event-related potential (ERP) study, which used the same vowel stimuli as the behavioral perception study, and sought to determine whether ERP methodology might provide a more sensitive measure than behavioral methods. Significant ERP effects were found in response to nearer-distance VV coarticulatory effects, but generally not for the longest-distance ones. This is the first ERP study to investigate the sub-phonemic processing associated with the perception of coarticulation.;In Part II, motion-capture technology was used to investigate LL coarticulation in the signing of five ASL users. Evidence was found of significant LL coarticulatory influence of one sign on another across as many as three intervening signs. However, LL effects were weaker and less frequent than the VV effects found in the spoken-language study. The perceptibility of these LL effects was then tested on both deaf and hearing subjects; some subjects in each group scored significantly better than chance on the task.