Abstract:  The oral vocabulary knowledge is a crucial factor for language development and school success for children, and develops rapidly in childhood. The present study was aimed to extend our current understanding of oral vocabulary knowledge development, at first by examining its growth from grades 1 to 3. Based on such findings, further question was asked about how to explain the individual differences in the growth rate of oral vocabulary acquisition. Therefore, the current research also investigated the additive effects of family socioeconomic status (SES), children’s phonological awareness, homograph awareness and compounding awareness on initial levels and growth rate in oral vocabulary knowledge. Participants were 149 children in grade one, who were followed up for three years from grade one entering to grade three. They were assessed on phonological awareness, homograph awareness, and compounding awareness at Time 1, oral vocabulary knowledge from Time 1 to Time 5. Family socioeconomic status was obtained from parents of these children. Latent growth modeling was conducted to examine: (1) children’s initial levels and growth rate in oral vocabulary knowledge over time; and (2) the predictive effects of family SES, phonological awareness, homograph awareness, and compounding awareness on both initial levels and growth rate in oral vocabulary knowledge. Unconditional latent growth modeling analyses revealed that children’s oral vocabulary knowledge increased in a non-linear trajectory during the follow-up period. In specific, (1) children showed individual differences in the initial levels and growth rate in oral vocabulary knowledge. (2) the initial level of oral vocabulary knowledge was not related to later growth rate. Conditional latent growth modeling was examined with family SES, phonological awareness, homograph awareness, and compounding awareness as time-invariant predictors on both initial levels and growth rate in oral vocabulary knowledge. It was found that (1) children who have higher level of phonological awareness, homograph awareness, and compounding awareness had higher initial levels of oral vocabulary knowledge than others did (β = 0.15, p < 0.05; β = 0.28, p < 0.001; β = 0.20, p < 0.05, respectively); (2) Family SES significantly predicted the initial levels of oral vocabulary knowledge (β = 0.35, p < 0.001); (3) Growth rate in oral vocabulary knowledge was predicted significantly by family SES (β = 0.26, p < 0.05) and children’s homograph awareness (β = 0.30, p < 0.01), respectively. The present findings have an important role in elucidating developmental changes of children’s oral vocabulary knowledge. It also highlights the predictive role of family SES, phonological awareness, homograph awareness, and compounding awareness in oral vocabulary development. More importantly, in the consideration of our findings that family SES and homograph awareness at Time 1 could predict growth rate in children’s oral vocabulary knowledge from T1 to T5. To improve the oral vocabulary knowledge for children, teachers need to pay special attention to children’s homograph awareness.

Key words: oral vocabulary knowledge, developmental trajectories, latent growth modeling, family SES, morphological awareness