Precursors to language in preterm infants: speech perception abilities in the first year of life

Language development in infants born very preterm is often compromised. Poor language skills have been described in preschoolers and differences between preterms and full terms, relative to early vocabulary size and morphosyntactical complexity, have also been identified. However, very few data are available concerning early speech perception abilities and their predictive value for later language outcomes. An overview of the results obtained in a prospective study exploring the link between early speech perception abilities and lexical development in the second year of life in a population of very preterm infants (≤32 gestation weeks) is presented. Specifically, behavioral measures relative to (a) native-language recognition and discrimination from a rhythmically distant and a rhythmically close nonfamiliar languages, and (b) monosyllabic word-form segmentation, were obtained and compared to data from full-term infants. Expressive vocabulary at two test ages (12 and 18 months, corrected age for gestation) was measured using the MacArthur Communicative Development Inventory. Behavioral results indicated that differences between preterm and control groups were present, but only evident when task demands were high in terms of language processing, selective attention to relevant information and memory load. When responses could be based on acquired knowledge from accumulated linguistic experience, between-group differences were no longer observed. Critically, while preterm infants responded satisfactorily to the native-language recognition and discrimination tasks, they clearly differed from full-term infants in the more challenging activity of extracting and retaining word-form units from fluent speech, a fundamental ability for starting to building a lexicon. Correlations between results from the language discrimination tasks and expressive vocabulary measures could not be systematically established. However, attention time to novel words in the word segmentation task yielded a significant correlation with vocabulary at both test ages. The predictive value of the behavioral measures in this research for an early identification of language delays in the preterm population was, thus, limited. However, early evidence of preterms' difficulties in speech and language processing tasks involving complex materials reveals a weakness in their initial approach to the language acquisition process that may constrain their future language skills well beyond the prelexical stage.