Factors Influencing Listener Comprehension in Multicultural Dysarthria

Abstract

The dysarthrias are a group of motor speech disorders which may be congenital, or may be acquired due to neurological injury or disease. Dysarthria frequently affects the intelligibility of speech, that is, the ability of the listener to decode the signals produced by the speaker, as well as the ability of the listener to understand the meaning of the speaker's message. As such, it has a great impact on the ability of the speaker to function in daily life and on quality of life. Most research is focused on the speaker with the impairment, but the listener plays a key role in the chain of communication. This study examined listeners in an attempt to describe some of the variables which may affect their ability to comprehend dysarthric speech. Given the multilingual and multicultural environment of South Africa, a particular focus was on language mismatch between speaker and listener. A mixed methods design was used in which the main aim was to identify barriers and facilitators of listener comprehension in dysarthria. Sub-aims were to compare the performance of listeners on tasks of intelligibility evaluation and comprehension; to identify the role of second language use in listener comprehension and intelligibility; to identify the role of experience in listener comprehension and intelligibility; to evaluate whether a training programme could be effective in improving listeners' comprehension and to describe the strategies used by a small group of successful listeners to decode dysarthric speech. The research comprised three sub-studies: The first quasi-experimental sub-study examined the variables of language use and experience in groups of listeners (n=93) on tasks evaluating the intelligibility and comprehensibility of the speech of four speakers with dysarthria; The second, qualitative sub-study focused on the listening strategies used by a small group of people (n=3) identified as being “successful” listeners; The third was an experimental study to investigate the effect of a training intervention, in which a group of 15 listeners were evaluated on intelligibility and comprehension tasks before and after receiving training. The results indicated that neither speaking the same language as the speaker nor previous iv experience with dysarthric speakers was a predictor of success in comprehending dysarthric speech. However, the combination of experience and matching language was a significant facilitator. The group who underwent the short training programme performed significantly better than the untrained control group, suggesting that training could be an important facilitator of comprehension. These results provide a very preliminary understanding of how the comprehension of dysarthric speech may be affected in the multilingual environment, a completely neglected area of research, and thus have potential theoretical implications as well as raising several implications for future research in the area. They also have important clinical implications, especially for resource-limited populations who do not have access to intensive rehabilitation, and for those whose dysarthria is progressive and whose speech will thus deteriorate. For both of these groups, greater focus on the listener, rather than the speaker, is likely to be more effective in improving communication.