| Author: | Chen, Fei |
| Title: | Cracking the speech code in tone language speakers with autism spectrum disorders : mechanisms and treatment |
| Advisors: | Peng, Gang (CBS) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Autistic children -- Language Communicative disorders in children -- Treatment Language disorders in children -- Treatment Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Chinese and Bilingual Studies |
| Pages: | xiv, 212 pages : color illustrations |
| Language: | English |
| Abstract: | Atypical auditory processing has been regarded as a potential factor related to pathological speech and language processing in individuals with Autism Spectrum Disorders (ASD). Motivated by the linguistic function of pitch in tone languages (such as Mandarin and Cantonese), several recent studies with Chinese people with ASD have provided an updated perspective in this field. Yet, our full understanding of speech processing difficulties and its underlying mechanisms and treatment in tone language speakers with ASD are still far from complete. This dissertation utilized auditory and speech stimuli varying in acoustic cue (spectral or temporal), sound type (speech or nonspeech), and linguistic relevance (native vs. non-native), to reveal the nature of speech processing difficulties in tone language speakers with ASD. Moreover, the training study proposed a music-assisted approach to help improve speech sound acquisition in Mandarin-speaking children with ASD. The first study compared the categorical perception (CP) of two prominent phonological features in Mandarin Chinese, lexical tones and voice onset time (VOT), which utilize pitch and time changes respectively to convey phonemic contrasts. Results indicated that the basic CP pattern of perceiving both native lexical tones and VOT was largely preserved in high-functioning adolescents with ASD, whereas the degree of CP of lexical tones was much higher than that of VOT. These findings suggest that the unbalanced acoustic processing capacities for pitch and time can be generalized to higher-level phonological processing in ASD. Furthermore, only in the real word condition, the Mandarin-speaking autistic individuals showed a "psychophysical boundary" similar to that observed in non-tonal language speakers who have no tonal language experience. The second cross-linguistic study evaluated the capacity of imitating complex Cantonese tones and their non-linguistic pitch counterparts in Cantonese-speaking (native) and Mandarin-speaking (non-native) children with and without ASD. Acoustic analyses showed that both native and non-native children with ASD could generally imitate the global tone contours for three level tones and three contour tones in Cantonese, pointing to a preserved acoustic pitch imitation skill in tone-language-speaking children with ASD. However, both Mandarin-speaking and Cantonese-speaking children with ASD exhibited atypical prosodic pitch pattern with increased pitch variations relative to TD children when imitating speech tones, but no group difference when imitating nonspeech sounds. Furthermore, unlike TD children, the non-native Mandarin-speaking children with ASD failed to exploit the phonological knowledge of the familiar segment to compensate for the imitation of syllables with an unfamiliar tonal category. These findings supported the notion that lexical tone imitation was largely intact at the bottom-up acoustic pitch processing level but impaired due to a top-down phonological processing deficit in individuals with ASD. The third training study evaluated the therapeutic potential of an adapted Melodic Intonation Therapy (MIT) in facilitating speech output for Mandarin-speaking nonverbal and low-verbal children with autism, in comparison with a matched non-MIT-based control treatment. Results indicated that our MIT-based treatment provided a more effective training approach in accelerating the rate of word and speech sound acquisition, especially lexical tone acquisition in the trained items. More importantly, the enhanced training efficacy on Mandarin tone acquisition remained at two weeks post-therapy, and generalized to novel items that were not practiced. These data provide the first empirical evidence for taking advantage of the cognitive strength of pitch processing in music, a ubiquitous nonspeech form, to compensate for the relative weakness of processing in speech sounds, especially lexical tones, in tone-language-speaking children with ASD. Taken together, the current findings in this dissertation lend support to the notion of speech-specific lexical tone processing difficulties in ASD. Furthermore, the high-functioning tone language speakers with ASD preserved the capacity to perceive or imitate the bottom-up acoustic pitch information of lexical tones, while showed deficits in exploiting the phonological information from the carrying syllables. Thus, speech processing atypicality in ASD is presumably to be not merely domain-specific and cue-specific but also language-dependent. Finally, the efficacy of music-assisted training approach was well proved for improving the spoken language in autistic children from a tonal language background, which adds a new clinical perspective to our understanding of the close relationship between music and speech. |
| Rights: | All rights reserved |
| Access: | open access |
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