What is it about?
Consonant and vowel distortions don't change the meaning of words they way phonemic errors do. Listeners hear them as subtle, yet incorrect, speech sound versions. Hearing sound distortions is an important criterion for diagnosing apraxia of speech. In this third study about audible consonant and vowel distortions in apraxia of speech, we examined audio-recordings from 66 people with speech sound production difficulties after left-hemisphere stroke or trauma. They were divided into 2 groups based on a single measurement of prosody. We reasoned that those who scored abnormally on the prosody measure would be likely to have apraxia of speech. Our coders were highly trained and equipped with audio recordings, headphones, and a narrow phonetic transcription system that included 29 distortion codes (diacritic marks).
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Why is it important?
The group who scored abnormally on the prosodic criterion for apraxia of speech produced more distortion errors than those who scored normally on this criterion. We think this means that distortion frequency helps separate people who have aphasia and apraxia of speech from those who have only aphasia. On the other hand, it seems the discrimination is far from perfect. Contrary to what traditional theories may have you believe, we found a lot of overlap between the groups.
Perspectives
I am so appreciative of the research assistants who were willing to spend months learning to transcribe disordered speech and then help us with the study. Thanks to their hard work, we can start to define much more precisely what we mean by distortion errors in aphasia and apraxia of speech. It is also easy to appreciate that behavioral syndromes like apraxia of speech and aphasia with phonemic paraphasia are multidimensional constellations with fuzzy boundaries. We need to understand what constellations are important for theory and practice and how we should define them quantitatively.
Katarina L Haley
University of North Carolina at Chapel Hill
Read the Original
This page is a summary of: Perceptually Salient Sound Distortions and Apraxia of Speech: A Performance Continuum, American Journal of Speech-Language Pathology, June 2017, American Speech-Language-Hearing Association (ASHA),
DOI: 10.1044/2017_ajslp-16-0103.
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