Of Assumptions and Biases

Of Assumptions, Biases, Horses, and Zebras

By Ken K. Gourdin

Some time ago at Nautilus, I read an interesting article on bias on the part of physicians (and possibly other medical personnel) in the Emergency Room. The article’s point is that practitioners can avoid diagnostic mistakes by avoiding too many assumptions. They shouldn’t simply assume that a patient who presents with certain symptoms has a common malady simply because, often, those symptoms are indicative of that common malady, nor should they assume that rare symptoms are not indicative of a common malady. See the article here (last accessed May 16, 2020):


A doctor-doctor, Robert Tomczak, an appellation I bestow upon him because, being the academic slouch that, plainly, he is, he has not just one but two doctorates, a Ph.D. and an M.D., respectively, opined, “My mentor in neuro-ophthalmology often said: ‘Common things are common and rare things are rare’, in other words a patient with blurred vision more likely needs a refraction for glasses than a brain MRI.”

That’s true as far as it goes, but I reminded the Good Doctor-Doctor that it is only half of the author’s point. I responded:

True enough, but, then, as I think this article points out (though it’s entirely possible I missed the point: by all means, correct me if you think that’s the case), that often, we think a particular thing (such as, in the case of physicians, a certain medical diagnosis) is more common it really is (or, for that matter, a person might think that a certain thing is much rarer than it actually is, or a physician might think diagnosis is much rarer than it actually is). Thus, the trick is in not missing a diagnosis because unconscious biases or assumptions might lead a physician to overestimate (or to underestimate) the actual probability of a certain diagnosis. I get your point, and I agree with it (as far as it goes). As I’ve heard it said in medicine (though I am neither a physician nor a healthcare provider): “Don’t be looking for zebras when you should be looking for horses.” As I read it, this article’s point, though, is a bit deeper than that: “Don’t allow your assumptions, your biases, and so on, to convince you that you’re looking at a horse just because the zebra you’re actually looking at resembles a horse in some ways.”

About kenngo1969

Just as others must breathe to live, I must write. I have been writing creatively almost ever since I learned to write, period! I have written fiction, book- and article-length nonfiction, award-winning poetry, news, sports, features, and op-eds. I hope, one day, to write some motivational nonfiction, a decent-selling novel, a stage play, and a screen play.
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