Características da fala materna e suas implicações para a aquisição inicial do vocabulário

Abstract

Over the past few years, several studies have been conducted to investigate the syntactic, prosodic and pragmatic aspects of child-directed speech (CDS). As a result of these studies, we now know that CDS is typically comprised of short and grammatically correct sentences, whose semantic content is restricted to the immediate context. However, the key characteristic of CDS is its prosodic variation and high pitch. Some authors have suggested that many of these features play an important role in language acquisition. In the present study, we investigated the characteristics of CDS in a group of Portuguese-speaking mother-child dyads in Brazil. We were particularly interested in investigating the relative frequency of different linguistic constructions in CDS and its impact on early vocabulary development. Apparently, this is the first study to investigate these questions in Portuguese. Participants were 35 mother-child dyads that were observed in a free-play situation in three different times: when the children were 9, 13, and 18 months of age. All observations were recorded and later transcribed and coded. At all times, mothers also completed the MacArthurs Communicative Development Inventory with the aim to provide information about the development of childrens expressive vocabulary. For each time, maternal utterances addressed to the child during the play session were classified according to the following types of linguistic construction: fragments (isolated words and sentence fragments), questions, imperatives, subject-predicate, copulasand complex sentences. Reliability, measured as the number of agreements divided by the number of agreements plusdisagreements between two independent coders, ranged between 0.88 and 0.90. Results showed a predominance of fragments, followed by imperatives, questions, copulas, subject-predicateand complex sentences, at all three times. Indeed, there was no difference in the incidence of these categories throughout the study. On the other hand,childrens vocabulary grew significantly over the study. Concurrent and longitudinal analyses were performed to investigate the relationship between CDS and childrens vocabulary growth. Overall, there was a trend for the number of nouns in childrens expressive vocabulary to correlate negatively with maternal use of imperatives, but positively with maternal use of copulas and questions. Few correlations were found between the incidence of fragments in CDS and children's vocabulary measures. These results are discussed in light of the hypothesis that some types of linguistic constructions in CDS, especially those that have a "frozen structure", play an important role in childrens language acquisition. For example, a very common type of copulain the speech of mothers who participated in the present study consisted of an invariant sequence of two or three words (e.g., "Here (is) the...", or That (is) the...) followed by a variable noun (e.g., kitty-cat, boy, etc.). It is possible that this kind of linguistic construction highlights the grammatical category "noun", thereby contributing to childrens acquisition of this type of words in the beginning of language acquisition.