Oral vocabulary has been found to play a direct role in reading and to predict later reading comprehension competence
Studies have shown that children who are less skilled in oral language at age 3 years and older have been found to be at a disadvantage in acquiring speaking, listening, and reading skills during formal schooling. In fact, many studies have shown that oral language and reading abilities are closely related. Joanne Lee takes this a step further and investigates the relationship between oral language ability at the earlier age of 2 and literacy development up to age 11 using a large longitudinal data set of typically developing children from the NICHD Study of Early Child Care and Youth Development (SECCYD).
The study, carried out in the USA, calculated the vocabulary size of 1,071 children (549 boys, 522 girls) aged 2, based on a checklist used to assess the receptive and productive vocabularies of children between ages 16 and 30 months and also between 30 and 37 months. The primary purpose of the study was to test whether early words measured at age 2 would significantly and uniquely predict subsequent language and reading skills of typically developing children. Three measures of early vocabulary were used to test which was the better predictor for later language and literacy development, (1) total vocabulary size (2) total number of verbs and (3) the proportion of verbs as function of total words. The children were put into large or small vocabulary groups if they fell in the top or bottom one-third of the list respectively. This was done for each predictor so that there were two distinct categories of children (those with large vocabularies and those with small vocabularies) for each predictor. The scores were then compared to sixteen language and literacy measures taken for the children at various stages between the ages of 3 and 11. These consisted of such things as verbal comprehension, expressive language, picture vocabulary and different aspects of literacy such as decoding skills, word recognition and reading comprehension.
After controlling for individual differences in terms of socio-economic group, gender, birth order (whether the child was first-born, second-born etc. in a family) and ethnicity, the findings of this study show that early expressive vocabulary can significantly predict language and literacy outcomes such as letter identification, phonological awareness, vocabulary and reading comprehension over the span of 9 years. The best predictor was the total vocabulary size followed by the total number of verbs which was also a good predictor. The proportion of verbs as a function of total words did not turn out to be a good predictor. Thus, children with a larger vocabulary size (or even total verb size) at age 2 continued to be on an advanced language and literacy development trajectory than their peers with a smaller vocabulary size.
One limitation of this study, acknowledged by the researcher, is that although early expressive vocabulary appears to predict subsequent language and literacy competence, the analysis does not explore the causal relationship between the two. Furthermore, measures of lexical composition other than the number of verbs produced, such as mean length of utterance or grammatical markers, could also be used to see whether these are better predictors of subsequent language and literacy than total vocabulary size.
However, despite these limitations, the results indicate that there is a continuum between early oral development and literacy development and the work underscores the importance of starting work on literacy development with children as young as two years old. The researcher concludes by urging parents, caregivers and early educators to provide a language-rich environment for children in the earliest years in order to lay a solid foundation for their language and literacy outcome later in life.
Lee. J. (2011). Size matters: Early vocabulary as a predictor of language and literacy competence. Applied Psycholinguistics 32: 69–92. doi:10.1017/S0142716410000299
This summary was written by Sue Fox