OBSERVATIONAL AND CHECKLIST MEASURES OF VOCABULARY COMPOSITION - WHATDO THEY MEAN

Observational and checklist measures of vocabulary composition have bo th recently been used to look at the absolute proportion of nouns in c hildren's early vocabularies. However, they have tended to generate ra ther different results. The present study is an attempt to investigate the relationship between such measures in a sample of 26 children bet ween 1;1 and 2;1 at approximately 50 and 100 words. The results show t hat although observational and checklist measures are significantly co rrelated, there are also systematic quantitative differences between t hem which seem to reflect a combination of checklist, maternal-report and observational sampling biases. This suggests that, although both k inds of measure may represent good indices of differences in vocabular y size and composition across children and hence be useful as dependen t variables in correlational research, neither may be ideal for estima ting the absolute proportion of nouns in children's vocabularies. The implication is that questions which rely on information about the abso lute proportion of particular kinds of words in children's vocabularie s can only be properly addressed by detailed longitudinal studies in w hich an attempt is made to collect more comprehensive vocabulary recor ds for individual children.