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 interrelationships
among the three language dimensions. Fifty-one European Portuguesespeaking
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.
This research was supported by European Regional Development Fund (FEDER) through the European program COMPETE (Operational Programme for Competitiveness Factors), under the National Strategic Reference Framework (QREN) - FCOMP-01-0124-FEDER-029556, by FCT (Fundação para a Ciência e a Tecnologia PTDC/MHC-PED/4725/2012), and by the Research Centre on Child Studies (CIEC-UM, reference POCI-01-0145-FEDER-007562). The first and fourth authors are also supported by grants SFRH/BPD/102549/2014 and SFRH/BD/86795/2012 from FCT.