Differences in the Semantic Structure of the Speech Experienced by Late Talkers, Late Bloomers, and Typical Talkers

The present study investigates the relation between language environment and language delay in 63 British-English speaking children (19 typical talkers (TT), 22 late talkers (LT), and 22 late bloomers (LB) aged 13 to 18 months. Families audio recorded daily routines and marked the new words their child produced over a period of 6 months. To investigate how language environments differed between talker types and how environments corresponded with children's developing lexicons, we evaluated contextual diversity-a word property that measures semantic richness-and network properties of language environments in tandem with developing vocabularies. The language environment experienced by the three talker types differed in their structural properties, with LT environments being least contextually diverse and least well-connected in relation to network properties. Notably, LBs' language environments were more like those of TTs. Network properties of language environments also correlate with the rate of vocabulary growth over the study period. By comparing differences between language environments and lexical network development, we also observe results consistent with contributions to lexical development from different learning strategies for expressive vocabularies and different environments for receptive vocabularies. We discuss the potential consequences that structural differences in parental speech might have on language development and the contribution of this work to the debate on quantity versus quality.