The influence of psycholinguistic variables on articulatory errors in naming in progressive motor speech degeneration

We describe an analysis of speech errors on a confrontation naming task in a man with progressive speech degeneration of 10-year duration from Pick's disease. C.S. had a progressive non-fluent aphasia together with a motor speech impairment and early assessment indicated some naming impairments. There was also an absence of significant phonological or semantic impairment. In order to examine naming difficulties and the factors that influence his speech production errors, we selected 210 words varying in frequency, age of acquisition (AoA), imageability, phonemic length and syllable length and conducted a logistic regression analysis on a range of speech production error types (phone omissions, additions, substitutions, response delays, overall errors). No significant naming errors due to lexical access were found. The only significant predictor of speech articulation errors was phonemic length, with none of the other lexical variables influencing speech production error. The only error type predicted was phone omissions. Results suggest that C.S.'s speech and naming errors indicate compromised speech programming/planning rather than lexical selection and we conclude that this pattern of findings is indicative of problems with motor speech production.