<p>Scientific reasoning is essential for developing learners’ higher-order thinking skills. Learners with different personality traits exhibit distinct behaviors and cognitive patterns in reasoning processes. However, school education often overlooks the cognitive patterns involved in scientific reasoning and rarely considers the impact of varying levels of personality traits on cognitive processes. This study aims to explore the impact of different personality traits on cognitive processes in scientific reasoning. We analyzed discussions from 70 university students during scientific reasoning tasks. Using ordered network analysis, we visualized epistemic networks to examine how personality traits shape cognitive processes during scientific reasoning. Significant differences emerged across the Big Five personality traits: For neuroticism, the low group adopted a bottom-up reasoning approach, beginning with concrete evidence before forming hypotheses, while the high group took a top-down, hypothesis-driven approach. For extraversion, the low group preferred independent problem-solving, whereas the high group actively engaged in social interactions to enhance reasoning. For openness, the low group showed a conservative style, contrasted by the high group's innovative thinking. For agreeableness, the low group was more independent, while the high group showed cooperation and attentiveness to others’ views. Lastly, for conscientiousness, the low group exhibited a casual cognitive style, whereas the high group demonstrated goal-oriented thinking. These findings provide insights for incorporating personality factors into group formation, which is crucial for enhancing the effectiveness of collaborative learning.</p>