The role of verbal working memory in new word learning in toddlers 24 to 30 months

Introduction. The purpose of this study was to evaluate the relative contribution of phonological loop capacity and of existing word knowledge to the ability of children 24-30 months to learn new words.;Methods. Children were tested at their home during the course of two sessions of about 45 minutes each. We took three measures for this study: a measure of the size of productive vocabulary using the Expressive Vocabulary Checklist of the Toddler's version of the MCDI (Fenson et al., 1993); a measure of phonological loop capacity using a non-word repetition task and a measure of expressive (naming) and receptive (recognition) fast mapping. We randomized both the measure of phonological loop capacity and the measure of word learning. The three measures performed were used to compute three statistics. A correlation between the phonological loop capacity and the size of the child's productive vocabulary indicated the strength of the relationship between those two variables. Multiple linear regressions computed the predictive value of phonological loop capacity and of the size of productive vocabulary to expressive fast mapping and to receptive fast-mapping.;Results. Findings revealed a moderate to strong positive correlation between phonological loop capacity and the size of productive vocabulary (r =.71, p<.01). Together, the phonological loop capacity and the size of expressive vocabulary explained 20% of the results in expressive fast-mapping (R2 = .20) and 48% of the results in receptive fast-mapping (R2 = .48). Findings also indicated that phonological loop capacity is a better predictor of both expressive and receptive fast mapping (β2 = .11, p = .02), than size of expressive vocabulary. Demographic findings indicated a moderate positive correlation between birth order and both size of productive vocabulary (r =.34) and nonword repetition scores (r =.43). Findings also showed a moderate positive correlation between maternal level of education and both size of productive vocabulary (ρ =.31) and nonword repetition scores (ρ =.49). Toddlers enrolled in care had a larger vocabulary size (Mean=358, SD=146) and lower non-word repetition scores (Mean=13.4, SD=5.7) than toddlers not enrolled. Females had larger vocabulary size (Mean=376, SD=168) and higher non-word repetition scores (Mean=16.2, SD=4.9) than males. Finally, age was not correlated with either of the independent variables.;Discussion. Typically developing toddlers 24 to 30 months old toddlers with large phonological loop capacity have a larger vocabulary size than toddlers with small phonological loop capacity. Toddler's phonological loop capacity is a better predictor of their ability to produce new words than the size of their productive vocabulary. This is true especially for toddler's ability to remember new words. As word learning involves complex cognitive processes, a variety of factors might affect their ability to remember, to retrieve and to produce new words. It is noteworthy that social environment also plays a significant role in toddlers' ability to learn new words.;Conclusion. Findings of this study confirm the positive relationship between verbal working memory and the size of toddler's productive vocabulary. They also provide preliminary evidence that verbal working memory contributes significantly to the ability of toddlers to learn new words. Those findings are consistent with the hypothesis of verbal working memory serving as a language learning device for children four years and older but extend the model to younger children. (Abstract shortened by UMI.).