Familiarisation conditions and the mechanisms that underlie improved recognition of dysarthric speech

Abstract

This investigation evaluated the familiarisation conditions required to promote subsequent and more long-term improvements in perceptual processing of dysarthric speech and examined the cognitive-perceptual processes that may underlie the experience-evoked learning response. Sixty listeners were randomly allocated to one of three experimental groups and were familiarised under the following conditions: (1) neurologically intact speech (control), (2) dysarthric speech (passive familiarisation), and (3) dysarthric speech coupled with written information (explicit familiarisation). All listeners completed an identical phrase transcription task immediately following familiarisation, and listeners familiarised with dysarthric speech also completed a follow-up phrase transcription task 7 days later. Listener transcripts were analysed for a measure of intelligibility (percent words correct), as well as error patterns at a segmental (percent syllable resemblance) and suprasegmental (lexical boundary errors) level of perceptual processing. The study found that intelligibility scores for listeners familiarised with dysarthric speech were significantly greater than those of the control group, with the greatest and most robust gains afforded by the explicit familiarisation condition. Relative perceptual gains in detecting phonetic and prosodic aspects of the signal varied dependent upon the familiarisation conditions, suggesting that passive familiarisation may recruit a different learning mechanism to that of a more explicit familiarisation experience involving supplementary written information. It appears that decisions regarding resource allocation during subsequent processing of dysarthric speech may be informed by the information afforded by the conditions of familiarisation.

Keywords:

• Dysarthria
• Perceptual learning
• Speech perception

Acknowledgments

We thank the participants with Parkinson's disease, and their families, for their participation in this study. We also gratefully acknowledge the contribution of the listener participants. Primary support for this study was provided by a University of Canterbury Doctoral Scholarship (Ms Borrie). Support from the New Zealand Neurological Foundation (Grant 0827-PG) and Health Research Council of New Zealand (Grant HRC09/251) (Dr McAuliffe) and National Institute on Deafness and Other Communicative Disorders Grant (R01 DC 6859) (Dr Liss) is also gratefully acknowledged.

Notes

¹Only speakers with dysarthria completed the SIT.

²The criteria for words correct were based on other published studies which have also examined listener transcripts following familiarisation with dysarthric speech (Liss et al., 2002, 1998; Liss, Spitzer, Caviness, Adler, & Edwards, 2000).