RESUMO
BACKGROUND: Overconfidence is the tendency to overestimate the knowledge, capacity, or performance one really possesses. This cognitive bias could be potentially dangerous in medical decision-making, considering the impact it could have on patient health care. The aim of this study was to evaluate the incidence of overconfidence and underconfidence in medical student knowledge on general surgery by using traditional and new statistical approaches. METHODS: During the application of a multiple-choice examination, 251 next-to-graduate medical students were invited to express the accuracy of their responses by choosing their own perceived confidence level for a set of questions. Analysis was done by comparing the difference between percentage of right answers (student's actual knowledge or accuracy) and self-estimated confidence level (student's perceived knowledge or confidence). Overconfidence was defined as a positive difference between confidence and accuracy, and underconfidence as a negative difference. RESULTS: Nearly 12% of students showed significant overconfidence regarding their actual knowledge or accuracy levels. Better students showed a lower overconfidence effect than students with poorer performance. On the other hand, underconfidence was less likely than overconfidence (8.3% of students), and that effect was most frequently found in students who performed better in examinations. CONCLUSIONS: The small proportion of our students exhibiting overconfidence or underconfidence behaviors moderates the need for educational interventions. Nevertheless, promoting prudence in individualized students manifesting overconfidence, and trust in those reporting significant underconfidence could increase the reliability of medical judgment during their future professional life. Overconfidence in individuals with lower scores in examinations may depend on a ceiling-like effect, since worst ranked students have a wider upper margin to manifest their confidence perceptions. The most confident students showed higher scores in examinations than the less confident ones. From this point of view, confidence could be considered an essential ingredient of success in examination performance.