A Systematic Review of Language Development in Simultaneous Bilinguals and Sequential Bilinguals: An Exploration from Cognitive Approach

This systematic review investigates the lexical and grammatical development of simultaneous and sequential bilinguals. Grounded in a cognitive approach, the review analyzes how age of second language onset, input quantity, and contextual variables influence bilingual language acquisition. Findings indicate that monolinguals generally outperform both bilingual groups in vocabulary and grammar tasks, although simultaneous bilinguals tend to perform comparably to monolinguals in receptive vocabulary. Results on lexical and grammatical performance among bilingual groups are inconsistent, potentially due to factors such as age, input quality, and task design. Notably, lexical-grammatical associations are found to be stronger within a single language than across languages, and more robust in the second language than the first among sequential bilinguals. The review highlights the need for longitudinal designs and larger sample sizes in future research to enhance generalizability and understand developmental trajectories more comprehensively.