BackgroundUncertainty in medical decision-making is a significant challenge influenced by various patient- and physician-related factors. They include physicians’ clinical reasoning skills and their tolerance for uncertainty. Medical students are trained in clinical reasoning and have to learn to manage uncertainty. This study investigates the influence of personality traits on the need for cognitive closure (NCC) among final-year undergraduate medical students participating in a simulation of a first day of residency.MethodsThe study included 373 students who participated in a simulation of a first day of residency between March 2022 and November 2023. The simulation included a consultation, a management, and a patient handoff phase, followed by self-assessments of confidence in clinical reasoning. We used the 16-Need for Cognitive Closure Scale (16-NCCS) and the HEXACO Personality Inventory - Revised (HEXACO-PI-R) to assess NCC and personality traits. Multiple linear regression analysis was performed to explore the impact of personality traits and gender differences on the NCC.ResultsOpenness, Extraversion, and Honesty-Humility negatively predicted NCC, suggesting these dimensions favor a more explorative and less hurried approach to medical decision-making. Conscientiousness and Emotionality positively predicted NCC, indicating a preference for structured and decisive processes among medical students with high scores on these dimensions. Notably, gender emerged as a significant moderator, particularly influencing the relationship between Emotionality and NCC, with female students showing a higher tendency towards seeking closure when Emotionality was high.ConclusionThe personality dimensions Openness, Extraversion, and Honesty-Humility are negatively predictive of medical students’ tendency towards cognitive closure. Learning to reflect on these interrelations is critical for medical students, as inappropriate responses to uncertainty can lead to poor medical decisions. Integrating self-reflective exercises into the curriculum could support students to recognize how their personality influences their response to uncertainty in medical practice.