Abstract
The advantage of Chinese-as-a-heritage-language (CHL) learners in acquiring Chinese has been widely recognized. However, it is still unclear whether the effect of CHL background on Chinese receptive vocabulary breadth varies across different countries. To address this gap, the present study recruited 232 Chinese language learners (half were CHL learners) from Indonesia and Thailand and administered a Chinese vocabulary proficiency test. The results of regression analysis revealed an interaction effect between country and CHL background on vocabulary breadth, with the contribution of CHL background to vocabulary breadth more robust in the Indonesian group than that in the Thai group. Interviews were then conducted to explore the factors that might influence such an interaction effect. Analysis of the interview data found that the influencing factors could be categorized into four themes, including individual differences, family background, Chinese language education and socio-cultural factors. The overall results were discussed within the framework of ecological system theory, and pedagogical implications for CHL learners were proposed.