Bowers, E.P., & Vasilyeva, M. (2011). The relation between teacher input and lexical growth of preschoolers. Applied Psycholinguistics, 32, 221-241.
This study examined the relationship between teacher speech and vocabulary (lexical) growth in 29 English language learners (ELL) of varying native languages, and 75 monolingual English preschoolers over the course of one academic year. Children’s lexical or word knowledge was assessed at the beginning and end of the same academic year using a well-accepted standardized vocabulary test, the Peabody Picture Vocabulary Test – Third Edition (PPVT-IIIB). In the middle of the school year, samples of teacher input were recorded from 10 classrooms over a 1.5 hour period that included circle time (group instruction), and snack time. Teacher speech was measured by input quantity (total number of words), lexical diversity (number of different words), and structural complexity (average number of words per utterance).
Results indicated that while the lexical growth of monolingual English speakers was significantly and positively related to the lexical diversity of teacher input with a relatively small effect size. In contrast, the lexical growth of ELLs was significantly and positively related to the quantity of teacher input but significantly and negatively related to the complexity of teacher input.
A possible explanation for this finding is that monolingual English preschoolers have already mastered the basics of English, and are therefore not thrown off by the lexical diversity. Instead, these children’s lexical growth is dependent on exposure to new words. In comparison, the ELL children have not yet mastered the basics of English and can be thrown off by the cognitive demand of complex utterances. These children benefit more from repetition of English words in simple sentences.
The main limitations of this study are the small sample size, particularly with respect to the ELL group, the single sample of teacher speech, and the lack of information provided about the teaching context (experience, class size, etc.). The strengths of this study include the novelty of comparing teacher speech to lexical growth of preschoolers (as it is typically parental speech that has been studied), and the promising suggestive results and effect size despite the small sample size.
Although the data is suggestive, it offers a promising path for future research in the area of language development and teacher input particularly highlighting the need to repetition in simple sentences to promote growth of word knowledge in children learning English whose first language is not English.
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