Maternal speech styles to children between 20 and 34 months of age who were slow to acquire expressive language were compared to those of mothers with normally speaking toddlers. Aspects of the mothers' speech examined included use of various sentence types (declaratives, negative, questions, etc.); the mother's lexical contingency with regard to the child's utterance; mother's use of pragmatic functions such as requests, comments, and conversational devices; and the mother's use of topic management. Results revealed that mothers of toddlers with slow language development are different from mothers of normal speakers only in their frequency of use of lexical contingency devices, specifically, expansion and extension. However, the proportion of expansions and extensions relative to the number of child utterances is not different, indicating that when late talkers give their mothers something to expand, the mothers do so, but that the late talkers do not give their mothers as much speech to work with as do the normal toddlers. Implications of these findings for parent training are discussed.
Paul, Rhea, Elwood, T.J. "Maternal Linguistic Input to Toddlers With Slow Expressive Language Development." Journal of Speech and Hearing Research 34.5 (1991): 982-988.