Early foreign language exposure and its dual effects on cognitive development and language competence in childhood
摘要
This systematic critical review synthesizes findings from 47 studies to examine the cognitive benefits and linguistic challenges associated with early foreign language exposure. The analysis reveals a complex picture: while multilingualism can enhance metalinguistic awareness (e.g., a 16% advantage in phonological segmentation accuracy) and executive function (aggregate d = 0.39), it may also coincide with short-term vocabulary deficits (12–18% smaller lexicons per language), grammatical delays, and socioemotional stress (e.g., 23% higher anxiety rates). Key moderators include cognitive ability, phonological memory, sociocultural context, and input quality. The findings challenge the "earlier is better" assumption, highlighting complex interactions between environment and development. The review concludes that structured bilingual programs, caregiver education, and additive language policies can mitigate risks while preserving cognitive advantages. Theoretically, the findings align with Dynamic Systems Theory, illustrating nonlinear, ecologically influenced growth. Practical recommendations include policy reforms, heritage language support, and differentiated instruction. Limitations, such as cultural biases in English-focused research and inconsistent exposure measures, underscore the need for longitudinal, cross-cultural studies. This review advances the argument for an equitable, context-sensitive framework for assessing early language exposure.