Purpose: Psychologists theorize that cognitive reasoning involves two distinct processes: System 1, which is rapid, unconscious, and contextual, and System 2, which is slow, logical, and rational. According to the literature, diagnostic errors arise primarily from System 1 reasoning, and therefore they are associated with rapid diagnosis. This study tested whether accuracy is associated with shorter or longer times to diagnosis.
Method: Immediately after the 2010 administration of the Medical Council of Canada Qualifying Examination (MCCQE) Part II at three test centers, the authors recruited participants, who read and diagnosed a series of 25 written cases of varying difficulty. The authors computed accuracy and response time (RT) for each case.
Results: Seventy-five Canadian medical graduates (of 95 potential participants) participated. The overall correlation between RT and accuracy was -0.54; accuracy, then, was strongly associated with more rapid RT. This negative relationship with RT held for 23 of 25 cases individually and overall when the authors controlled for participants' knowledge, as judged by their MCCQE Part I and II scores. For 19 of 25 cases, accuracy on each case was positively related to experience with that specific diagnosis. A participant's performance on the test overall was significantly correlated with his or her performance on both the MCCQE Part I and II.
Conclusions: These results are inconsistent with clinical reasoning models that presume that System 1 reasoning is necessarily more error prone than System 2. These results suggest instead that rapid diagnosis is accurate and relates to other measures of competence.