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The Etiology of Individual Differences in Second Language Acquisition in Australian School Students: A Behavior-Genetic Study


  • This research was supported by funds from the Language Learning Round Table Conference Program and was facilitated through the Australian Twin Registry which is supported by an Enabling Grant from the National Health & Medical Research Council administered by The University of Melbourne.

William Coventry, Discipline of Psychology, University of New England, Armidale, NSW 2351, Australia. Internet:


We present one of the first behavior-genetic studies of individual differences in school students’ levels of achievement in instructed second language acquisition (ISLA). We assessed these language abilities in Australian twin pairs (maximum N pairs = 251) by means of teacher ratings, class rankings, and self-ratings of proficiency, and used the classic twin design to estimate the relative influences of genes, shared (family/school) environment, and unique environment. Achievement in ISLA was more influenced by additive genetic effects (72%, 68%, and 38% for teacher ratings, class rankings, and twin self-ratings, respectively) than by shared environment effects, which were generally not substantial (20%, 07%, and 13%). Genetic effects distinct to speaking and listening, on the one hand, and reading and writing, on the other, were evident for the twin self-ratings. We discuss the limitations and implications of these findings and point to research questions that could profitably be addressed in future studies.