Intended for healthcare professionals

Education And Debate

Five pitfalls in decisions about diagnosis and prescribing

BMJ 2005; 330 doi: (Published 31 March 2005) Cite this as: BMJ 2005;330:781
  1. Jill G Klein (, associate professor of marketing1
  1. 1INSEAD, 1 Ayer Rajah Avenue, 138676 Singapore
  • Accepted 1 February 2005

Everyone makes mistakes. But our reliance on cognitive processes prone to bias makes treatment errors more likely than we think


Psychologists have studied the cognitive processes involved in decision making extensively and have identified many factors that lead people astray. Because doctors' decisions have profound effects on their patients' health, these decisions should be of the best possible quality. All doctors should therefore be aware of possible pitfalls in medical decision making and take steps to avoid these unnecessary errors. In this article, I present five examples of cognitive biases that can affect medical decision making and offer suggestions for avoiding them.

Psychology of decision making

Doctors often have to make rapid decisions, either because of medical emergency or because they need to see many patients in a limited time. Psychologists have shown that rapid decision making is aided by heuristics—strategies that provide shortcuts to quick decisions—but they have also noted that these heuristics frequently mislead us.1 Good decision making is further impeded by the fact that we often fall prey to various cognitive biases.

To make correct decisions in clinical practice, doctors must first gather information on which to base their judgments. According to decision making experts Russo and Schoemaker,2 the best way to do this is to ask the most appropriate questions, to interpret answers properly, and to decide when to quit searching further. Straightforward though this sounds, misleading heuristics and cognitive biases create pitfalls throughout this process.

Doctors may believe that, as highly trained professionals, they are immune to these pitfalls. Unfortunately, they are just as prone to errors in decision making as anyone else.35 Even worse, it is common for people who are particularly prone to cognitive biases to believe that they are good decision makers.2 As Shakespeare put it, “The fool doth think …

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