Early lexical development: the contribution of parental labelling and infants' categorization abilities.

In the present longitudinal study, we examined changes in parental labelling and infants' categorization skills as potential predictors of vocabulary composition, the age of the naming explosion, and the acquisition of subordinate labels. Sixteen French- and English-speaking parent-child dyads were videotaped during a 20-minute free-play session every month beginning when the child was 1;0 and ending at 2;0. The children received object-manipulation tasks every three months and their vocabulary growth was recorded. Parental labelling practices were assessed monthly using a picture-book reading task. Both parental labelling and children's categorization skills predicted the content of children's lexicon, with children with more names in their vocabulary having better categorization skills. Furthermore, the naming explosion was found to coincide with improvement of categorization skills. These findings suggest that the influence of each factor varies as a function of the stage and aspect of lexical development considered.