Saturday, June 11, 2022

Indulge me in a little metacognition

I found an interesting post about cognitive shortcuts in medicine. I have a minor objection to the title of the post which is Cognitive Errors. Cognitive shortcuts, known as heuristics, which are examples of fast instinctive thinking (system one), often lead to error. In some cases, however, they can be useful because they are efficient and time saving. There is an up side as well as a down side to system one thinking in medicine.

Let’s go down the list. I’ve skipped some of them.

The first example given is affective error. This refers to an emotional response surpassing objectivity.

Next is aggregate bias. I struggle with this one. The author says that the aggregate bias is the belief that data in the aggregate don’t apply to the patient in front of you. My understanding (maybe I’m wrong) is that aggregate bias, otherwise known as the ecological fallacy, is the opposite. That is, it refers to inappropriate application of population data to an individual. It has more to do with treatment decisions than diagnostic error. Remember, one of the first principles of evidence-based medicine is that clinical reasoning decision making starts with the unique aspects of the individual patient. After looking at a variety of references, it would appear that both definitions have been used. Most medical references define aggregation bias the way the blog author does. Those outside of medicine define it as inappropriate extrapolation.

The ambiguity effect is really a bias against ambiguity. So we tend to stick with things we are more familiar with. That may cause us to ignore other possibilities and take too narrow a view of things. As originally conceived it had to do with probability. That is, people have a tendency to gravitate toward choices in which the probability is known or explicitly stated. Of note, the ambiguity effect was first described by Daniel Ellsberg.

The anchoring heuristic is one of the better known cognitive biases. This refers to the tendency to stick with one’s initial hunch despite new evidence to the contrary. You may be so proud of your initial hunch that you ignore new information. Confirmation bias and diagnostic momentum are related concepts.

Ascertainment bias, as the author points out, is an umbrella category. It encompasses a lot of stereotypes and biases. In essence it’s just—-well, bias. It’s not very useful as a unique category in discussions of cognitive error.

Availability bias is one of the better known cognitive shortcuts. This refers to the influence of prior experience. This causes bias toward the first thing that comes to your mind. For example, if you’ve been burned by having missed a case of aortic dissection you may tend to be over concerned about aortic dissection in every future case of chest pain. The flip side is you may fail to consider things you haven’t seen in a long time.

Base rate neglect is a cognitive shortcut that may be considered harmful and wasteful in ambulatory medicine but may be your friend in the arena of hospital and emergency medicine. It’s a failing to consider the true prevalence of diseases in clinical reasoning. It ignores the old aphorism “common things happen most often.” In the high acuity world of the hospital, where you really need to be risk-averse, base rate neglect may be beneficial. Put another way you and and your patient may be better off if you consider worst case scenario.

Then there’s belief bias. I’m not sure this belongs in a discussion of diagnostic shortcuts as it has more to do with treatment recommendations. I cringe when I hear somebody say they “believe“ in a particular treatment, implying that belief surpasses reasoning from evidence .

Blind spot bias is similar to the Dunning Kruger effect in which we think we're smarter than we really are. Humility is the remedy here. Does this lead to a form of cognitive shortcut? Maybe in that we fail to pause and consider carefully that we might be wrong.

Confirmation bias is akin to anchoring. This is the tendency to be selective in what type of accumulating evidence you consider. That is, you consider mainly evidence that supports your original hunch.

The framing heuristic is another well known shortcut. We are biased toward diagnostic possibilities in accordance with the way the initial presentation is framed. Though it can be useful it restricts our differential diagnosis in a way that excludes a wide range of possibilities. Not every returning travel with fever has a parasite, for example.

The gamblers fallacy, according to the blog author, is “the erroneous belief that chance his self correcting.“ This is a cognitive error that tends in the opposite direction to the availability heuristic.

The order effect is something I was vaguely aware of but had not considered as a cognitive error category. It refers to the tendency to focus on information that is proximate in time and to do so at the expense of the totality of events over time. This typically occurs at the point of hand off in a patient who has had a very long hospital course.

Premature closure is just what it says. It’s a tendency for thinking to stop once a tentative diagnosis has been made. It overlaps with other categories such as anchoring. There is probably a subtle difference between premature closure and anchoring. Anchoring implies an emotional attachment to a diagnosis whereas premature closure implies diagnostic laziness.

Representativeness restraint has also been known as a representativeness heuristic. It is a cognitive shortcut characterized by focusing too much on the prototypical manifestations of a disease. This may cause the clinician to miss atypical presentations.

Search satisfaction is another example of laziness in clinical reasoning. It’s a tendency to stop searching once an answer has been found. The author gives the example of missing a second fracture on an x-ray once the first one is identified.

Sunk cost fallacy is a type of emotional heuristic as well as diagnostic laziness. It is the tendency to ignore new information and not consider alternative diagnoses once the original diagnosis has been arrived at after a great time effort and expense (the sunk cost).

Sutton’s slip might be the dark side of Sutton’s law (going where the money is). Pursuing the obvious might lead to error because of other possibilities being ignored.

Zebra retreat is the avoidance of rare diagnoses to a fault. It’s an opposite of base rate neglect.

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