Segmental diagnostics of neurogenic and functional foreign accent syndrome

Abstract Previous research suggests differences in speech patterns between speakers with foreign accent syndrome (FAS) associated with a neurological (neurogenic FAS) versus a psychological aetiology (functional FAS). Differentiating sub-types holds important clinical implications, affecting the nature of follow-up assessment and treatment. To date, there exist no systematic comparisons between these sub-groups. To investigate possible differences, we employed auditory and acoustic analyses to compare schwa insertion and /r/production in speakers with FAS (12 neurogenic, 5 functional). Schwa insertion and /r/ production demonstrated significant differences between groups. Neurogenic aetiology was associated with higher within and between speaker performance consistency and congruence of derailments with phonetic-phonological and neurological accounts of ‘error’ origin. Individuals with functional FAS showed significant within and between speaker variability, which was poorly accounted for by linguistic and speech motor control explanations. We argue that schwa insertion and differences in /r/ realisations provide reliable and accessible variables for clinicians to employ to support differential diagnosis of functional versus neurogenic speech disorders. Findings are discussed in the context of understanding FAS and the broader context of understanding functional speech and language disorders.