Maternal speech disfluency: How it relates to lexical diversity, syntactic complexity, and child language outcomes Open Access
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Disfluencies have been examined by many different fields. Examination of disfluencies gives valuable insight into the internal nature of the speech production process and listeners' perspectives. Disfluencies include filled pauses, hesitations, and repetitions. It has been found that factors including syntactic complexity (i.e. grammar) and lexical diversity (i.e. vocabulary) influence the production of disfluencies. When speakers direct speech to particular listeners, changes in lexical diversity and syntactic complexity can occur. These changes can be seen when speaking to infants, children, and adults and are referred to as speech registers. The registers are referred to as infant-directed speech (IDS), child-directed speech (CDS), and adult-directed speech (ADS). The exact changes across these three registers are still somewhat unknown. Recent research suggests infants and children are sensitive to disfluencies and may use disfluencies for language learning. This study followed a group of 40 mothers speaking to their infant during a play session at 11-months of age, then again at 24-months of age, and finally to an adult. This allowed for changes in lexical and syntactic complexity to change naturally across the three different conditions. Disfluency rates and linguistic measures including lexical diversity and syntactic complexity were measured for each condition. A repeated measures MANOVA revealed differences in fluency, lexical diversity, and syntactic complexity among the registers. Spearman correlation coefficients revealed no significant relationships between fluency rates and lexical diversity or syntactic complexity. Spearman correlation coefficients revealed a significant relationship between fluency rates and child receptive language standardized test scores.