L1 Influence on Familiar and Unfamiliar L2 Idiom Comprehension: An Investigation Across L2 Proficiency Levels

Research in bilingualism has repeatedly demonstrated the profound challenge bilinguals experience with L2 idioms due to their opaque figurative meanings. Despite the attempts to reveal significant influences on this challenging task, studies and models usually fail to consider all key determinants, either due to demanding sample sizes or due to the simple omission of potential effects. While individual idiom characteristics are commonly examined in the literature, the interplay between L1 influence, idiom familiarity, and L2 proficiency in L2 idiom comprehension is usually overlooked. By recruiting a large pool of bilinguals (n = 251) across varying L2 proficiency levels, this study primarily focused on these interactive variables from a developmental perspective. Additionally, idiom characteristics (transparency and imageability) and individual differences (L2 Age of Acquisition, reading exposure, and listening exposure) were explored as secondary factors. The analyses revealed distinct developmental trajectories. Familiar L2 idioms seemed to follow holistic processing patterns, while unfamiliar L2 idiom comprehension was likely to be affected by crosslinguistic influences. In particular, the findings indicated a developmental path in which bilinguals abandon surface-level L1 lexical overlap with increasing L2 proficiency and rely more on conceptual features, with L1 lexical overlap becoming inhibitory. In addition, the findings suggested that imageability could decrease L2 idiom comprehension accuracy, while L2 reading and listening exposure could boost accuracy and comprehension speed. Overall findings suggest that current idiom comprehension models require fundamental modifications in order to account for the dynamic and proficiency-dependent nature of bilingual idiom comprehension.