Although the phenotypic correlation between language and nonverbal cognitive ability is well-documented, studies examining the etiology of the covariance between these abilities are scant, particularly in very young children. The goal of this study was to address this gap in the literature by examining the genetic and environmental links between…

Quantity and quality of caregiver input was examined longitudinally in a sample of 50 parent-child dyads to determine which aspects of input contribute most to children's vocabulary skill across early development. Measures of input gleaned from parent-child interactions at child ages 18, 30, and 42 months were examined in relation to children's…

Children vary widely in the rate at which they acquire words--some start slow and speed up, others start fast and continue at a steady pace. Do early developmental variations of this sort help predict vocabulary skill just prior to kindergarten entry? This longitudinal study starts by examining important predictors (socioeconomic status [SES],…

Working class and upper-middle class mothers were videotaped interacting with their toddlers in four settings. Samples of the mothers' adult-directed speech were also collected. Observed were social class differences in the mothers' child-directed speech and some parallel differences in the mothers' adult-directed speech. This may reflect more…