title: Genetic evidence for bidirectional effects of early lexical and grammatical development.
abstract: This article addresses the autonomy hypothesis of vocabulary and grammar and bootstrapping mechanisms in early language development. Two birth cohorts of 1,505 and 1,049 same-sex twin pairs from the UK were assessed at 2 and 3 years on grammar and vocabulary, using adapted versions of the MacArthur Communicative Development Inventory. Vocabulary and grammar correlate strongly at both 2 and 3 years in both cohorts. Multivariate genetic modeling reveals a consistently high genetic correlation between vocabulary and grammar at 2 and 3 years. This finding suggests the same genetic influences operate for both vocabulary and grammar, a finding incompatible with traditional autonomy hypothesis, at least in early acquisition. Crosslagged longitudinal genetic models indicate both lexical and syntactical bootstrapping operate from 2 to 3 years.
authors.affiliation: Ecole de psychologie, Université Leval, Québec, Qc, Canada. ginette@psy.ulaval.ca
authors.forename: Ginette
authors.initials: G
authors.lastname: Dionne
authors.forename: Philip S
authors.initials: PS
authors.lastname: Dale
authors.forename: Michel
authors.initials: M
authors.lastname: Boivin
authors.forename: Robert
authors.initials: R
authors.lastname: Plomin
mesh_terms: D002663:Child Language; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008037:Linguistics; D008297:Male; D011795:Surveys and Questionnaires; D014427:Twins / Q000235:genetics*