Predicting the predictors: Individual differences in longitudinal relationships between infant phonetic perception, toddler vocabulary, and preschooler language and phonological awareness.

摘要

Despite evidence indicating the importance of phonological sensitivity in early literacy, few studies have investigated predictors of preschool phonological awareness (PA) starting in infancy. With exposure to the ambient language, sensitivity to native contrasts generally increases over the first year of life, though there is wide variability in how this develops. This dissertation addresses how individual differences in preverbal phonetic perception are related to toddler and preschool language and PA, a documented precursor to reading. In a longitudinal sample (N=25), phonetic sensitivity was measured behaviorally at ages 7 and 11 months through native vowel discrimination. Vocabulary development was measured at ages 18 and 24 months, and general language, PA, home literacy environment, and SES were measured at age 5 years using standardized tools.;Results suggest a positive relationship between phonetic sensitivity at 7 months and PA in preschool, after controlling for overall cognition, language, and SES. Analyses of individual trajectories revealed three distinct subgroups of infants who showed either comparatively low phonetic sensitivity at both 7 and 11 months, a marked increase in sensitivity, or consistently high sensitivity. The Low-Low group had an average vocabulary about half as large as the other groups at 18 and 24 months, was less likely to combine words at 24 months, and scored about a half-standard deviation lower than the other groups on language tests at 5 years. The Low-Low and Low-High subgroups performed nearly one standard deviation lower than the High-High subgroup on advanced PA tasks at 5 years. Predictions were improved when home literacy environment was considered.;Together, findings suggest that individual learning trajectories around native language phonetic sensitivity within the first year of life predict aspects of language and pre-literacy skills through at least 5 years. Specifically, pre-verbal infants who demonstrate greater early sensitivity, and/or the greatest growth in sensitivity, to native phonetic cues tend to show greater and earlier proficiency at phonological awareness in preschool, especially when coupled with an optimal home literacy environment. Results are consistent with current models of early language and literacy development, where domain-general cognitive ability is likely to influence observed relationships.