Miller, D.J., Spengler, E.S., & Spengler, P.M. (2015). A meta-analysis of confidence and judgement accuracy in clinical decision making. Journal of Counseling Psychology, 62, 553-567.
People can make errors in judgements based on decision making rules that are biased. Clinicians also may be prone to making such errors. In their Nobel Prize winning work, Kahneman and Tversky outlined a number of heuristics (i.e., mental shortcuts) that lead to cognitive biases, which in turn affect accuracy of decisions. For example, when making a differential diagnosis clinicians may: rely too heavily on only one piece of information which may be the most available (e.g., “I vividly remember a patient with conversion disorder who had the same history”); or ignore that a particular event (e.g., conversion disorder) is very rare; or seek confirming rather than disconfirming evidence (e.g., the patient has PTSD symptoms that can explain some symptoms). Complicating these biases is the tendency for clinicians to be over-confident. For example, in one study the average psychotherapist rated their performance as better than 80% of their peers, and no therapist rated him or herself in the lower 50th percentile among peers. In their meta analysis, Miller and colleagues reviewed 36 studies of the relationship between clinician confidence ratings and accuracy of decisions among 1,485 clinicians. The authors were particularly interested in the overconfidence bias, which occurs when individuals report higher confidence in their judgments than is warranted by their actual accuracy. For example, studies have assessed the impact of clinician confidence on clinical accuracy in: detecting random responding on a psychological test, diagnosing a brain disorder verified by medical test using neuropsychological test data, predicting future violence and recidivism in offenders, and patient progress in psychotherapy. Most studies find that clinicians are quite confident in their judgments. But, is this confidence warranted? Miller and colleagues’ meta analysis found a significant but small (r = .15) association between confidence and accuracy. This suggests that clinician confidence is only slightly indicative of decision-making accuracy. The effect was a little larger for more experienced clinicians (r = .25), indicating that more experience and training resulted in somewhat more consistency between a clinician’s confidence and their clinical accuracy. Further, higher confidence leads to poorer accuracy when clinicians have to make repeated decisions without feedback, when feedback is not written, and when an event is rare.
Clinicians, like everyone else, are sometimes subject to making errors when they only look at confirming evidence, when they rely only on their own memory rather than objective data, and when they are over-confident. Accuracy can be increased when clinicians use decision-making aids that provide quality corrective feedback. Aids to help in decision making might include the use of: objective standardized test data, repeated measurements with feedback to assess patient progress in psychotherapy, and actively looking for disconfirming evidence before making a clinical judgement. As the authors conclude, confidence is not a good substitute for accuracy.