The effect of outcome information on doctors' evaluations of their own diagnostic decisions.
BACKGROUND
Outcome bias is a psychological tendency to use outcome information in order to evaluate the quality of a previous decision, where decisions with bad outcomes are undervalued and decisions with good outcomes are overvalued. In some circumstances, being affected by outcome when evaluating a diagnostic decision might have important educational consequences: bad diagnostic decisions resulting, by chance, in good outcomes might be repeated in the future, whilst good diagnostic decisions with bad outcomes might be abandoned. However, no previous studies have tested whether outcome bias affects doctors' evaluations of their own diagnostic decisions.


METHODS
A total of 91 practising Italian doctors (69 general practitioners, 22 neurologists) chose a diagnosis for a neurological case and then evaluated it after receiving outcome information (positive outcome, adverse outcome or no outcome).


RESULTS
Outcome information affected the doctors in many ways: the quality of the decision was overrated following good outcomes, and underrated following bad outcomes; the difficulty of making the diagnosis was underrated after good outcomes and overrated after bad outcomes, and the memory of weightings assigned to signs and symptoms consistent with the diagnosis was overrated after good outcomes and underrated after bad outcomes (and vice versa for the weighting of evidences inconsistent with the diagnosis).


CONCLUSIONS
Outcome bias in medical decisions is discussed in terms of its possible adverse effects on doctors' learning and knowledge revision processes: although sensitivity to outcomes may be desirable in some circumstances, in other circumstances it can cause either the fixing of incorrect knowledge or the improper revision of correct knowledge.
Sacchi
Simona
S
Department of Psychology, University of Milano-Bicocca, 20126 Milan, Italy.
Cherubini
Paolo
P
D000328:Adult; D001291:Attitude of Health Personnel; D002983:Clinical Competence / Q000592:standards*; D003657:Decision Making; D005260:Female; D006801:Humans; D007558:Italy; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000175:diagnosis*; D009462:Neurology / Q000592:standards; D010821:Physicians, Family / Q000592:standards; D010818:Practice Patterns, Physicians' / Q000592:standards*