This article investigates the relationship between third person singular present tense agreement morphemes, copula "is" and verb-"s", at 2;00 and 2;03. Language samples from 60 children at 2;00 were analyzed for the productivity of copula "is" as measured by the number of different morphemes preceding "is"…

Purpose: The goals of this study were to quantify longitudinal expectations for verb lexicon growth and to determine whether verb lexicon measures were better predictors of later grammatical outcomes than noun lexicon measures. Method: Longitudinal parent-report measures from the MacArthur-Bates Communicative Development Inventory (Fenson et al.,…

Purpose: 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. Method: Child growth in third person sentence diversity was modeled from 21-30 months (n = 38) in conversational language samples obtained…

Purpose: Evidence for tense marking in child-directed speech varies both across languages (Guasti, 2002; Legate & Yang, 2007) and across speakers of a single language (Hadley, Rispoli, Fitzgerald, & Bahnsen, 2011). The purpose of this study was to understand how parent interaction styles and register use overlap with the tense-marking…