The development of vocabulary and grammar: a longitudinal study of European Portuguese-speaking toddlers.

The goals of this study were to analyze the growth and stability of vocabulary, mean length of the three longest utterances (MLLUw), and sentence complexity in European Portuguese-speaking children aged 1;4-2;6, to explore differences in growth as a function of personal and family-related variables, and to investigate the inter-relationships among the three language dimensions. Fifty-one European Portuguese-speaking toddlers were longitudinally assessed at 1;4, 1;9, 2;1, and 2;6, through parent reports. Exponential growth models best described acquisition patterns during this period, but the vocabulary growth accelerated across the full age-range, whereas the growth of grammar dimensions accelerated mainly after 1;9. High variability was observed in the scores, but the toddlers' relative positions were mostly stable over time. Gender approached significance as a predictor of vocabulary growth. Maternal educational level did not predict the growth of any of the three language dimensions. Both vocabulary and MLLUw predicted sentence complexity.