Overconfident AI? Benchmarking LLM Self-Assessment in Clinical Scenarios

Background and Aim: Large language models (LLMs) show promise in healthcare, but their self-assessment capabilities remain unclear. This study evaluates the confidence levels and performance of 12 LLMs across five medical specialties to assess their ability to accurately judge their responses. Methods: We used 1965 multiple-choice questions from internal medicine, obstetrics and gynecology, psychiatry, pediatrics, and general surgery. Models were prompted to provide answers and confidence scores. Performance and confidence were analyzed using chi-square tests and t-tests. Consistency across question versions was also evaluated. Results: All models displayed high confidence regardless of answer correctness. Higher-tier models showed slightly better calibration, with a mean confidence of 72.5% for correct answers versus 69.4% for incorrect ones, compared to lower-tier models (79.6% vs 79.5%). The mean confidence difference between correct and incorrect responses ranged from 0.6% to 5.4% across all models. Four models showed significantly higher confidence when correct (p<0.01), but the difference remained small. Most models demonstrated consistency across question versions. Conclusion: While newer LLMs show improved performance and consistency in medical knowledge tasks, their confidence levels remain poorly calibrated. The gap between performance and self-assessment poses risks in clinical applications. Until these models can reliably gauge their certainty, their use in healthcare should be limited and supervised by experts. Further research on human-AI collaboration and ensemble methods is needed for responsible implementation. Keywords: Large Language Models (LLMs), Safe AI, AI Reliability, Clinical knowledge.