Cognitive Traps

In my recent review of Peter Palmieri’s book Suffer the Children I said I would later try to cover some of the many other important issues he brings up. One of the themes in the book is the process of critical thinking and the various cognitive traps doctors fall into. I will address some of them here. This is not meant to be systematic or comprehensive, but rather a miscellany of things to think about. Some of these overlap.

Diagnostic fetishes

Everything is attributed to a pet diagnosis. Palmieri gives the example of a colleague of his who thinks everything from septic shock to behavior disorders are due to low levels of HDL, which he treats with high doses of niacin. There is a tendency to widen the criteria so that any collection of symptoms can be seen as evidence of the condition. If the hole is big enough, pegs of any shape will fit through. Some doctors attribute everything to food allergies,  depression, environmental sensitivities,  hormone imbalances, and other favorite diagnoses.  CAM is notorious for claiming to have found the one true cause of all disease (subluxations, an imbalance of qi, etc.).

Favorite treatment.

One of his partners put dozens of infants on Cisapride to treat the spitting up that most normal babies do.  Even after the manufacturer sent out a warning letter about babies who had died from irregular heart rhythms, she continued using it. Eventually the drug was recalled.

Another colleague prescribed cholestyramine for every patient with diarrhea: not only ineffective but highly illogical.

When I was an intern on the Internal Medicine rotation, the attending physician noticed one day that every single patient on our service was getting guaifenesin.  We thought we had ordered it for valid reasons, but I doubt whether everyone benefited from it.

Recognizing warblers.

Like birdwatchers, hospitalists like Palmieri learn to identify which doctor admitted a patient. Child doesn’t appear sick; admitting diagnosis is “occult bacteremia”; patient was given an intramuscular injection of Cephotaxime in the office — oh, that must be Dr. X.

Rapid identification vs pareidolia

Humans are good at pattern recognition. This allows experienced clinicians to make rapid diagnoses, but it also allows us to see the Virgin Mary on a grilled cheese sandwich.

Rooster syndrome

Rooster crows, sun comes up; therefore rooster made sun come up. Baby had colic, was given treatment X, colic resolved; therefore X cures colic. In reality, colic resolves spontaneously by 3-4 months of age and X was useless.


Mimicking what other physicians in the community are doing.


Choosing a drug because you have samples handy that the drug rep left.

Ulysses syndrome

Ulysses went from one adventure to another in the odyssey of returning home from the Trojan War. A false positive test can lead to a fruitless odyssey of further investigation: tests lead to more tests, maybe even invasive procedures and harm to the patient. Eventually it is realized that the patient has been healthy all along.

Unnecessary lab tests

Sometimes tests are done in a scattershot attempt to find something, anything. Palmieri’s pathologist wife directs a laboratory and frequently gets calls from doctors who have ordered an unfamiliar test and have no idea what to do when they get an abnormal result. Instead of getting an individual chemistry test, we get SMAC panels because the machine is there and it’s so convenient and cheap. With 20 tests on these panels, there is a 66% probability that at least one test will be outside normal limits on a perfectly healthy normal person.

Defensive medicine

With the present legal climate, doctors sometimes do tests or treatments with an eye to how things would look in court, rather than for the direct benefit of the patient.


Ordering tests to impress the patient that the doctor is being thorough and is actually doing something.

Hardwired fallibility

Our brains do not function in a rational, objective, logical way. We have built-in psychological mechanisms and defects in information processing; our brains have evolved a repertoire of tricks and shortcuts that serve us well in everyday life but that must be overcome for critical thinking and science.

Confirmation bias

Once we form a belief, we seek out evidence that confirms it and reject evidence that contradicts it. We are all biased, but by being aware of our biases we can activate a self-correcting mechanism.


We form opinions about the many based on our experience of a few. We may base our idea of a disease on a patient who had an atypical presentation, or tend to avoid using a drug because of a patient who had an uncommon side effect. Radiologists who have missed a diagnosis are tempted to over-interpret x-ray findings for a time afterwards.


We tend to reach an early diagnosis and cling to it even when subsequent evidence doesn’t fit. We tend to accept the diagnosis of the referring physician rather than going back to square one to make up our own mind.

Diagnosis momentum

An early possibility becomes a presumptive diagnosis and gains legitimacy as it is repeated by more and more health care providers.


We seek a diagnosis within the context of how the information is presented to us. Palmieri tells about a boy who presented with “frequent throat infections.” He was referred to ENT and even had a tonsillectomy before it was discovered that he had never even had a sore throat, only unexplained fevers that had been falsely attributed to throat infections but that eventually turned out to be due to juvenile rheumatoid arthritis.

Miscommunication and assumptions

Palmieri describes a case where an ENT consultant was called in directly by the worried parents of a child hospitalized with an ear infection. He assumed that they and the pediatrician must have wanted him to put in PE tubes; otherwise there would have been no earthly reason for a consult. He had booked an OR and scheduled the patient for surgery before it became clear that the child had a first ear infection that was responding to treatment, that ENT input was unnecessary, and that PE tubes were clearly not indicated.


We simplify our approach to complex problems by following algorithms like “if the white count is over 15,000, give antibiotics.” This is not always appropriate. Algorithms provide a convenient framework, not an unalterable directive.

Tunnel vision

We are cautioned against thinking of zebras every time we hear hoofbeats, but we often fall into the opposite trap: we tend to fixate on the diagnoses we commonly see in our practice and not consider rare possibilities. On a recent episode of the television show “Untold Stories from the ER” there was a toddler who was refusing to walk because of leg pain. They took x-rays looking for fractures to confirm their initial diagnosis of child abuse. It turned out he had scurvy, a vitamin C deficiency that simply doesn’t occur in the 21st century US — but it did, because he was refusing all foods but oatmeal and his uneducated parents didn’t know there was anything wrong with catering to his wishes.


In medical school, doctors learn science but they may not learn to think like a scientist. Once out in practice, they become vulnerable to unproven claims, myths, and pseudoscience; and they are encouraged to give advice based on common sense and intuition rather than on evidence. Not just doctors but everyone needs to better understand the cognitive traps we all fall into. Since our human brains are inherently fallible, only critical thinking and good science can keep us on track. A major theme of this blog is that good science is essential for correcting our errors.

Posted in: Science and Medicine

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32 thoughts on “Cognitive Traps

  1. Ken Hamer says:

    Your list of “cognitive traps” applies equally (and remarkably) well to other fields as well, including mine (electronic navigation systems.) We frequently get reports from both end users and technicians with a range a diagnosis similar to the above.

  2. Diane Jacobs says:

    “In medical school, doctors learn science but they may not learn to think like a scientist.”
    (Way too sadly) true for my field, physiotherapy. Almost all the other examples apply as well.

    Thank you for this post.

  3. Kylara says:

    This was interesting (and definitely, as Ken points out, a good list of common HUMAN cognitive traps). I want a word for a “reverse” diagnostic fetish (although maybe it’s still just a diagnostic fetish); a year into a relationship with a doctor in a new town, he informed me, “I don’t believe in sinus infections — people just get headaches and think the world is ending.” (While I realize they’re overdiagnosed, he didn’t “believe in” them at all ever!)

    He followed this up at my next visit by insisting that depression in women was mostly just complaining and they should “try to be less sad, it’s not like there’s anything wrong with their lives, they’re not starving to death” and that loss of libido in a MARRIED woman wasn’t a legitimate problem because, “You’re already married, your husband can just suck it up.”

    This is how I learned the importance of interviewing doctors before deciding to create a relationship with them. And I’m DELIGHTED to pay for an office visit out of pocket to do so.

    In college, one of the campus health doctors treated everything with either gatorade (hangover, flu), a Z-Pak (respiratory infections, sinus headaches, even if allergy-caused), or reading glasses (other headaches). He also based most of his diagnoses on “what was going around” on campus; students with mono frequently ended up diagnosed with strep throat, and vice versa, which is weird because I thought both tests were pretty cheap. I suppose you visit enough doctors over the course of a few decades and you’re bound to run into some real doozies who allow laziness to lead them into epic cognitive traps.

    (and geez, scurvy? Public health in the U.S. needs a booster injection of money badly!)

  4. weing says:

    One of my favorite topics. For a nice listing of cognitive biases check out

  5. CarolM says:

    Personally I got tired of the catch all “depression” diagnosis when it showed up in the 80s, probably because Prozac was in da house. Yeah you get depressed when your life is all in flux but so what. My doc’s answer was, we’ll give you the drug and if you feel better, we’ll know that’s what it was. My problems weren’t any that exercise and caffeine management wouldn’t fix, and the drugs gave me weird nervous tics that I could not put up with.

    In the 70s it was something else again. The doctor would get a terribly concerned look on her face and askare you under a lot of stress? Uh, yeah I play in a band every night, mess around doing pursuing my hobbies every day, and make good money. Lotta stress there. Oh well!

    It’s things like this that made me veer dangerously toward CAM but I’m better now.

  6. Ed Whitney says:

    Some of these cognitive biases in medicine are associated with deeper biases induced by the socialization of physicians. “You’re a doctor; do something” bias permeates the entire health care system, leading to many kinds of overtreatment. The need to act comes first; the rationale for acting comes later.

    George Bernard Shaw nailed it 100 years ago in “The Doctor’s Dilemma.” Cutler Walpole is a surgeon who has a single explanation for everything: “Ninety-five per cent of the human race suffer from chronic blood-poisoning, and die of it. It’s as simple as A.B.C. Your nuciform sac is full of decaying matter—undigested food and waste products—rank ptomaines. Now you take my advice, Ridgeon. Let me cut it out for you. You’ll be another man afterwards.”

    Confirmation bias appears to be part of human nature. There is strong statistical evidence that there is no such thing as a hot hand in basketball, but just try to watch the NBA playoffs and deny that players are hot or not in particular games.

    There is an article in the current “Behavioral and Brain Sciences,” whose abstract is at . This article is likely to become widely quoted and cited. The authors propose that the function of reason is primarily argumentative rather than cognitive; we reason in order to be able to persuade others of our intuitively arrived at opinions rather than to arrive at truth. A preliminary copy of the entire paper is at .

    If reason’s function is primarily social, then it requires considerable effort to adapt it to a different purpose, namely sitting alone and using it to arrive at a position which may contradict our own intuitions and argumentative preferences. Medical schools would have to teach students to transcend their own human nature, and this would entail instruction at a higher logical level than is used in preparing them to pass the standardized tests upon which their fate so often depends.

  7. Kylara “He followed this up at my next visit by insisting that depression in women was mostly just complaining and they should “try to be less sad, it’s not like there’s anything wrong with their lives, they’re not starving to death”

    When I was experiencing some depression a number of years ago, my brother called me up and said “What’s the problem? You have a good life, a good job, you’re healthy, how could you be depressed?”

    I told him “That’s kinda the point.” Meaning, everything is fine in my life, yet I can’t seem to feel anything positive, and I’ve really tried. That doesn’t seem normal.

    If the quality of the air is fine and yet you still can’t catch your breath, it seldom helps to hear about how fresh the air is. :)

  8. windriven says:

    Seriously now, we all know that nitrous oxide deficiency is the one true cause of all disease ;-)

    Where’s daedalus when we need him?

  9. I think I probably got a good dose of Ulysses syndrome when I was a kid (and framing, and anchoring). In a nutshell, I suffered some weird symptoms for years during my teens after receiving anabolic steroid therapy for slow growth syndrome. In retrospect, I was probably “healthy all along,” but the rare treatment I’d received completely framed the terms of the diagnostic investigation. My family and I were convinced it had to be the steroids, and several of the doctors involved certainly treated it like that, at least at first.

    A couple of naturopaths, of course, just loved the steroids theory and they probably greatly exacerbated our trumped up fear that I’d been poisoned by mainstream medicine. Sigh.

  10. Jayhox says:

    I shared this article with a fellow skeptical dentist, who aptly replied:

    “I disagree that doctors or dentists learn science in professional school. They learn science facts, but absolutely nothing about the scientific method, or experimental design, or bullshit detection.  Realtively few, with science degrees, have had any of that.”

    So very true, and sad.

  11. Ed Whitney says:

    “…but absolutely nothing about the scientific method, or experimental design, or bullshit detection.”

    Or even how to ask a question, for that matter. Answering questions, yes, yes, and yes again, responding with as many right answers, and as few wrong answers, as is humanly possible. Graduate school teaches something about asking questions, how to narrow the focus of a question until it is amenable to research, and how to approach a tentative answer to the question.

    In another context, it is quite something to have a president who can welcome some disconfirmation of assumptions; if you saw the 60 Minutes interview the other night, you heard him say that the people with the negative assessments of the bin Laden raid were invaluable in making the operation a success. To be able to listen to someone say, “That’ll never work, Mr. President,” and to take in that opinion and process it cerebrally, and to value the disconfirmation of the previously held opinion, is of value not only in science but in statecraft.

  12. norrisL says:

    Sadly I have to agree with you. 5 years of university education to gain a degree in veterinary science and how much did we learn of the scientific method? Nothing! I never heard the term until long after graduation. Just a little bit of education on the scientific method at school or university may have “vaccinated” some of my peers against being sucked into homeopathy and other such garbage.

  13. Harriet Hall says:

    College is too late. We should start teaching the scientific method and critical thinking skills in grade school. There is a great book “Nibbling on Einstein’s Brain” by Diane Swanson that is appropriate for that age, funny, with cartoons.

  14. Daniel M says:

    Maybe the two small state universities I attended are exceptions, but I feel I got a very good grounding in understanding and putting into practice the scientific method during my pre-med undergrad. Almost every chemistry and biology class went over the scientific method at least in the first couple lectures, and in the labs we discussed the topic, wrote numerous lab reports, and even designed experiments for ourselves (research with faculty was also encouraged and widely available). Perhaps college science education used to be worse (I graduated last year), but anyone with a science undergrad really should have a fairly solid understanding of the scientific method and I’m surprised people are saying they know science majors who haven’t even heard the term. I will grant that logical fallacies, biases, and cognitive errors were not stressed anywhere near enough, including in the classes I took for my psychology minor.

    I agree with Dr. Hall that college is too late to expect most people to learn critical thinking. Many people who buy into woo never went to college, or went and got non-science degrees, so this has to be stressed early at home and in schools. I was homeschooled through 10th grade and went to a small Christian school my last two years, and if I hadn’t been a science major because I wanted to be a doctor I’d still probably be into all kinds of pseudoscience. (For example, my sole high school science class was earth science, and we attended mandatory young earth creationist conferences by Ken Ham and Kent Hovind. So you can imagine that I was pretty confused at how science and critical thinking worked when I started college.)

  15. When I was in middle school and high school I had a few teachers who talked about critical thinking, a history teacher, a citizenship teacher, an American lit teacher.

    I believe that my sixth grade science teacher taught a simplified scientific method. I’m surprised that my 11th grade biology teacher didn’t, because it really seems like something he would have taught. I was out a week sick once, maybe I missed it.

    I have a point. I have friends from the same school, who in many cases had the same teachers, very smart friends who where in gifted and EP classes who got much better grades then me and went on to careers in science, who will swear up and down they were not taught critical thinking.

    You know how memory is…maybe people who are good at memorizing and calculating just tend to remember facts better or find facts more exciting. I don’t know, but I think it’s curious.

  16. BillyJoe says:

    “Seriously now, we all know that nitrous oxide deficiency is the one true cause of all disease ;-)
    Where’s daedalus when we need him?”

    I also thought of daedalus whilst I reading this article last night, but I didn’t feel cruel enough to put it in print. :D

  17. windriven says:

    Ah, he can take it Billy Joe. Daedalus is a smart guy. But when you have a big investment in a really nice hammer, every problem starts to look like a nail.

  18. tmac57 says:

    This discussion demonstrates to me the need for patients to also have a better understanding of these cognitive traps,and how they affect their own thinking as well as their heath care provider.But we,as patients,are constantly told to trust our doctor’s expertise over our own naive views of what is the best path for our care.This seems sensible on the face of it,yet what we are describing here shows an unsettling fact of human frailty,that leaves me feeling wary of placing my full trust into the hands of my physicians,yet lacking the education to do otherwise.I have just enough understanding of the pitfalls of medical practices to cause me to be careful,but no clear idea of what to do about it.

  19. “Unnecessary lab tests” really should be relabeled as scattershot soething-or-other, which should include both referrals/consults, and lab tests.

    Doing C/L psych, we recognize a similar pattern: a physician makes a consult for either neuropsych testing or personality testing, and does not have a clear diagnostic question to answer in the consult (worse than the usual lousy referral question), and upon examining the patient’s chart, we see consults scattershot all over the hospital.

    This doesn’t just happen on “House.”

    We shrug and conclude what is happening: the physician does not know what is going on, and has sent out a bunch of consults all at once, scattershot, hoping to hit something.

  20. The hammer/nail discussion is great.

    I have figured out yet another fristrating example of hammer/nail: when you are a bureaucrat or administrator, your job is to keep track of the people who are actually performing and delivering your core mission. The administrators and bureaucrats are just helping keep things coordinated and managed.

    So, to them, everything works by keeping track of things.

    Their hammer is the form. Or procedure.

    So, any problem, nail, gets addressed with their hammer: some new form to fill out, or some new bureaucratic procedure: it might be training, or signing a memo, or, well, you know all-too-well.

    This is why providers/clinicians eventually get flooded with forms and recording and reporting that eats up time and contributes little value.

  21. James Fox says:

    I’d add that the list of cognitive traps explain the path to fervent religious beliefs as well as anything. Cognitive dissonance detection is a skill best exercised daily and in all aspects of life.

  22. …we all know that nitrous oxide deficiency is the one true cause of all disease…

    As happy as nitrous oxide might make everyone feel, D2u’s DOC is nitric oxide. Couldn’t resist making the point, bein’ an anesthesiologist.

  23. # Kimball Atwoodon 11 May 2011 at 1:50 pm
    “As happy as nitrous oxide might make everyone feel, D2u’s DOC is nitric oxide. Couldn’t resist making the point, bein’ an anesthesiologist.”

    Thanks! I’ve been somewhat baffled on that point for quite a while now.

  24. tmac57 says:

    As happy as nitrous oxide might make everyone feel, D2u’s DOC is nitric oxide. Couldn’t resist making the point, bein’ an anesthesiologist.

    Just say ‘NO’.

  25. daedalus2u says:

    Just to point out a cognitive trap, if you don’t know the difference between nitric oxide and nitrous oxide (despite my best efforts ;) ), you don’t know enough about either of them to be able to evaluate what role they might (or might not) have in disease (or health).

    Cognitive traps are easy for everyone to get into. They are mental shortcuts that sometimes work. Sometimes they don’t work, but the only way you can know if the short cut is not working is to figure it out the hard way, without using the shortcut.

    You can’t substitute another shortcut.

  26. Artour says:

    Based on hundreds of medical studies, I also believe that chronic diseases have one cause. This cause is abnormal breathing, which for mild or moderate forms of diseases is manifested in chronic hyperventilation – present in 100% of patients with heart disease, asthma, diabetes, cancer, cystic fibrosis, and so forth. Just consider this Table with over 45 medical studies that measured breathing rates (minute ventilation) in the sick:
    Bear in mind that tissue hypoxia promotes (or others say causes) cancer, angina pain, diabetes, cystic fibrosis, etc. with tens more studies that support the idea.

  27. Actually, I think that Artour is getting very close on “The One True Cause of Disease.” His only problem is that he didn’t go far enough.

    The one true cause of disease is not breathing…

    it is living.

  28. Josie says:

    Yep. My Mom raised me with the adage that Life is a chronic STD and 100% fatal.

  29. tmac57 says:

    The one true cause of not breathing is dying.

  30. Thoughts on this Psychology Today article about Dexamethasone in pregnancy being “safe for mother and child”?

  31. SkepticalRN says:

    I would add another trap of Recency. As a nurse I would observe the residents fall into jags of diagnoses, tests, or meds based on what they were discussing in rounds or at a presentation. They would last about a week or two until something newer came along. When the drug rep came I could always count on a rise in prescriptions for whatever he was promoting.

    The trap seems to be that we are more likely to remember things that happened recently. This is often seen by pollsters who find that people give more weight to current than long past events.

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