China
Second language (L2) learners’ awareness of first language-second language (L1–L2) semantic differences plays a critical role in L2 vocabulary learning. This study investigates the long-term development of eight university-level Chinese English as a foreign language learners’ cross-linguistic semantic awareness over the course of 10 months. A longitudinal multiple-case study approach was adopted and the learners’ introspective think-aloud protocols, elicited by a custom-built vocabulary depth test, were explored. Qualitative data analysis of the learners’ verbal reports revealed that the development of cross-linguistic semantic awareness was slow, unpredictable, and characterised by phases of incremental growth, stabilisation, and attrition. The fluctuating development of such awareness implicates the deep entrenchment of L1 lemma information and a competitive relationship between L1 and L2 lemma information. The pedagogical implications for instructed L2 vocabulary learning and teaching are that continued reinforcement is needed to draw learners’ attention to the overall differences of the L1 and L2 lexical systems.