Beyond the foreign language effect: unravelling the impact of l2 proficiency on rationality

Abstract This study investigated the impact of reading statements in a second language (L2) versus the first language (L1) on core knowledge confusion (CKC), superstition, and conspiracy beliefs. Previous research on the Foreign Language Effect (FLE) suggests that using an L2 elicits less intense emotional reactions, promotes rational decision-making, reduces risk aversion, causality bias and superstition alters the perception of dishonesty and crime, and increases tolerance of ambiguity. Our results do not support the expected FLE and found instead an effect of L2 proficiency: Participants with lower proficiency exhibited more CKC, were more superstitious and believed more in conspiracy theories, regardless of whether they were tested in L1 or L2. The study emphasises the importance of considering L2 proficiency when investigating the effect of language on decision-making and judgements: It—or related factors—may influence how material is judged, contributing to the FLE, or even creating an artificial effect.