Exploring the Genetic and Environmental Etiologies of Phonological Awareness, Morphological Awareness, and Vocabulary Among Chinese–English Bilingual Children: The Moderating Role of Second Language Instruction

This study investigated the associations among bilingual phonological awareness, morphological awareness, and vocabulary by focusing on their genetic and environmental etiologies. It also explored the influence of family socio-economic status (SES) and language exposure amount on the genetic and environmental effects. A twin study was conducted with 349 pairs of Chinese–English bilingual twins (mean age = 7.37 years). Cross-language transfer was found in phonological and morphological awareness but not in vocabulary knowledge. A common genetic overlap was found among these bilingual abilities. We also found a common shared environmental effect that may account for the cross-language transfer in phonological awareness and the associations among English abilities. SES and language exposure were significant environmental influences on bilingual phonological awareness and English vocabulary. More teaching in Chinese was related to a stronger genetic effect on Chinese morphological awareness, whereas more teaching in English was related to a stronger environmental impact on English abilities.