Speech disfluencies in children with developmental dyslexia: How do they differ from typical development?

BACKGROUND Disfluency is a multifactorial concept that can be linked to several of the language production levels, in both typical and atypical populations. In children, the language system is still developing and few studies have explored disfluency patterns. In typical development (TD), in particular, studies have shown discrepancies according to the language being considered. In neurodevelopmental disorders, such as developmental dyslexia (DD), it is still unclear whether the pattern of disfluency is similar to TD. AIMS To analyse the type of disfluency and their evolution in French children aged 8-12 years. Also to compare the pattern of disfluency in DD and TD, and to test whether disfluencies were correlated with reading difficulties. METHODS & PROCEDURES A total of 25 children with DD and 21 children with TD aged 8-12.6 years produced an autobiographical narrative. Seven types of disfluencies were coded: part-word repetitions; repetitions of monosyllabic words; other types of repetitions (words and phrases); filled pauses; revisions-substitutions; revisions-additions; and abandoned utterances. We compared the proportion of each disfluency in DD and TD. Spearman correlations were then performed between disfluencies, reading performance and age. OUTCOMES & RESULTS The results showed that both DD and TD children mainly produced filled pauses, repetitions of monosyllabic words and substitutions. Both groups displayed a high rate of disfluency (> 10%). No correlations with age were found. Correlations with reading performance were significant in the TD group only. CONCLUSIONS & IMPLICATIONS The study showed that DD is not characterized by a specific pattern of disfluency. Additionally, disfluency rates were similar in children aged 8-12 years. In contrast to other languages, the current study suggests that French-speaking children have a high rate of disfluency. The study also suggests that disfluency should be interpreted with caution in DD, given that TD children also have a high rate of disfluency. Therefore, it seems important to adapt the pathological threshold of disfluency to the language being spoken in order to avoid an overestimation of the prevalence of these deficits in French-speaking children. WHAT THIS PAPER ADDS What is already known on this subject TD children produce a high rate of disfluency, which is also influenced by the language being spoken. No study looked at the effect of DD on disfluency production. Nonetheless, problems in reading comprehension and reduced reading experience may impact lexical development and speech fluency. What this paper adds to the existing knowledge In our study, both groups (French-speaking children) produced a substantial amount of disfluency as compared with other languages (> 10%). Additionally, the pattern of disfluency was similar in TD and DD (namely, filled pauses, prolongations repetitions of monosyllabic words and substitutions). In the DD group, disfluency production was not correlated with reading performance. What are the potential or actual clinical implications of this work? These results indicate that it is crucial to consider the language being spoken when examining disfluency in order to avoid an overestimation of language difficulties in some languages, such as in French. Moreover, the production of disfluencies in DD should not be considered as language dysfunction since the pattern of disfluency what quite similar in TD and DD, and did not correlate with their reading difficulties.