So I’m reading through this Wikipedia list of cognitive biases , and it’s pretty apparent that almost all of these factor in to our discussions of patient care. A sample, with the definitions provided by the Wikipedia:

• belief bias – the tendency to base assessments on personal beliefs (see also belief perseverance and Experimenter’s regress) All the time. We assume things about patients–what they do, how they act–based on our own understanding of “normal.”
• bias blind spot – the tendency not to compensate for one’s own cognitive biases. We don’t have to compensate. We’re the doctors; we’re right, duh.
• confirmation bias – the tendency to search for or interpret information in a way that confirms one’s preconceptions. Uh, pertinent positives and negatives? If I suspect cirrhosis, I’ll ask you about alcohol. And if you tell me you have 1-2 drinks a night, someone will say the “rule of doubling” so that you actually drink 2-4 drinks a night.
• disconfirmation bias – the tendency for people to extend critical scrutiny to information which contradicts their prior beliefs and accept uncritically information that is congruent with their prior beliefs. If I suggest someone might have HIV, someone usually says he or she “doesn’t have any HIV risk factors.” Translation: I think he or she is married or heterosexual, so they can’t possibly have HIV.
• endowment effect – the tendency for people to value something more as soon as they own it. If it’s lymphadenopathy, I don’t brag about my patient. But when it turns out to be fetus in fetu, I talk all about him.
• hyperbolic discounting – the tendency for people to have a stronger preference for more immediate payoffs relative to later payoffs, the closer to the present both payoffs are. Should we keep a patient or discharge her tonight? Discharge; it’s one less note to write in the morning.
• illusion of control – the tendency for human beings to believe they can control or at least influence outcomes which they clearly cannot. Oh boy. This just about sums up the physician mind.
• mere exposure effect – the tendency to express undue liking for things merely because they are familiar with them. “She’s just another CHF/COPD exacerbation.”
• planning fallacy – the tendency to underestimate task-completion times. “I’ll be right up to see the patient;” “He’ll be getting his CT at 2:30;” “The dictation should be online by tomorrow.”
• rosy retrospection – the tendency to rate past events more positively than they had actually rated them when the event occurred. “No, really, internship’s not that bad.” “This won’t hurt a bit, I had it done when I was your age.”
• selective perception – the tendency for expectations to affect perception. You label a person as “really nice,” and your team will probably think they’re nice. Label them as cranky or grouchy, and they’ll expect someone to be grouchy.
• status quo bias – the tendency for people to like things to stay relatively the same. We’re happy when the creatinine stays at baseline. We like uneventful hospital stays.
• Von Restorff effect – the tendency for an item that “stands out like a sore thumb” to be more likely to be remembered than other items. Attendings give anecdotal evidence: “During my residency I saw an Asian person with sarcoid, so it happens more often than you’d think!”
• Zeigarnik effect – the tendency for people to remember uncompleted or interrupted tasks better than completed ones. This is the intern’s defense mechanism. Everything gets done because you know you haven’t completed it yet, and no one else is going to do it for you.
• fundamental attribution error – the tendency for people to over-emphasize personality-based explanations for behaviors observed in others while under-emphasizing the role and power of situational influences on the same behavior. A person is over-emotional if they cry.
• ingroup bias – preferential treatment people give to whom they perceive to be members of their own groups. Hell yeah. If you say you’re Dr. So-And-So, you have a lot more clout that if you say, “I’m the medical student taking care of Ms. Jones.”
• self-serving bias – the tendency to claim more responsibility for successes than failures. It may also manifest itself as a tendency for people to evaluate ambiguous information in a way beneficial to their interests. “We really got her through that acute renal failure well” versus “She was really sick when she came in.”

Note: I’m not saying these happen all the time. Just that they can, and we’ve got to be on the lookout for them.

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