Covert contrast in the speech of an adolescent with Apraxia of Speech : a case study

Churchill, Kimberley (2009) Covert contrast in the speech of an adolescent with Apraxia of Speech : a case study. Masters thesis, Memorial University of Newfoundland.

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Abstract

This is a case study of Marshall, a 15-year-old with Apraxia of Speech (AoS). AoS is an articulatory disorder affecting ability to program speech musculature. This thesis examines Marshall's production of the approximants /r, l, w, j/. In singleton onsets Marshall's /r/ sounds like /w/, ‘red’ [wεd]. For reasons outlined in the thesis, we expect Marshall to produce a contrast between /w/ and /r/ in singleton onsets, however, Marshall appears to produce both as [w]. This apparent lack of contrast prompted this investigation into the possibility of a “covert” contrast between /r/ and /w/ (a difference that is measurable but not perceivable to listeners). Marshall's approximants in singleton onsets were acoustically analysed. Statistical analysis revealed contrasts between all four approximants. Furthermore, acoustic correlates of /r/ and /w/ were statistically different indicating covert contrast. Verifying the existence of covert contrast in an individual with AoS may have implications on the diagnosis and treatment of such speech disorders.

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