title: Input Subject Diversity Enhances Early Grammatical Growth: Evidence from a Parent-Implemented Intervention.
abstract: OBJECTIVE
  The current study used an intervention design to test the hypothesis that parent input sentences with diverse lexical noun phrase (NP) subjects would accelerate growth in children's sentence diversity.
  
  
  METHODS
  Child growth in third person sentence diversity was modeled from 21 to 30 months (n= 38) in conversational language samples obtained at 21, 24, 27, and 30 months. Treatment parents (n= 19) received instruction on strategies designed to increase lexical NP subjects (e.g.,The baby is sleeping.). Instruction consisted of one group education session and two individual coaching sessions which took place when children were approximately 22 to 23 months of age.
  
  
  RESULTS
  Treatment substantially increased parents' lexical NP subject tokens and types (ηp2≥ .45) compared to controls. Children's number of different words was a significant predictor of sentence diversity in the analyses of group treatment effects and individual input effects. Treatment condition was not a significant predictor of treatment effects on children's sentence diversity, but parents' lexical NP subject types was a significant predictor of children's sentence diversity growth, even after controlling for children's number of different words over time.
  
  
  CONCLUSIONS
  These findings establish a link between subject diversity in parent input and children's early grammatical growth, and the feasibility of using relatively simple strategies to alter this specific grammatical property of parent language input.
authors.affiliation: Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign.
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Hadley
authors.affiliation: Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign.
authors.forename: Matthew
authors.initials: M
authors.lastname: Rispoli
authors.affiliation: Illinois Educational Research Council, Southern Illinois University Edwardsville.
authors.forename: Janet K
authors.initials: JK
authors.lastname: Holt
authors.affiliation: Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign.
authors.forename: Theodora
authors.initials: T
authors.lastname: Papastratakos
authors.affiliation: Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign.
authors.forename: Ning
authors.initials: N
authors.lastname: Hsu
authors.affiliation: Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign.
authors.forename: Mary
authors.initials: M
authors.lastname: Kubalanza
authors.affiliation: Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign.
authors.forename: Megan M
authors.initials: MM
authors.lastname: McKenna
keywords: child-directed speech; language intervention; parent input; syntax; toddlers