Deliberate reasoning is not affected by language

Background Millions of people use a second language every day. Does this have an effect on their decision-making? Are decisions in a second language more deliberate? Two mechanisms have been proposed: reduced emotionality or increased deliberation. Most studies so far used problems where both mechanisms could contribute to a foreign language effect. Here, we aimed to identify whether deliberate reasoning increases for problems that are devoid of any emotional connotation when using a second language or having to switch between native and second language. Method We measured deliberate reasoning with items from the cognitive reflection test, ratio bias, a probability matching task, and base rate neglect items. We recruited over 500 participants from Norway and the Netherlands that had English as their second language. Participants were randomly assigned to either the native, switching or second language condition. We measured: number of correctly answered items-deliberate reasoning score, perceived effort, perceived accuracy or confidence, and language proficiency. Results Deliberate reasoning was not increased when using a second language or when having to switch between native and second language. All three groups performed equally well. Significant predictors of deliberate reasoning were age, gender, education, perceived effort, and confidence but not the language context. Participants with low English proficiency spent more time reading compared to more fluent speakers. Conclusion There is no advantage of second language on deliberate reasoning in the absence of time pressure. Deliberation was not increased by providing items in a second language, but through the willingness to spend cognitive effort and time to read carefully.