Scepticism regarding common sense

Thank you for a thought-provoking article that provided a glimpse at the chasm between the current state of evidence-based medicine (EBM) and ideal clinical practice.1

While I agree that considerable scepticism is required in the interpretation of EBM and the clinical trials upon which it is based, I submit that common sense requires at least as much scepticism in its implementation.

The human brain is not particularly good at accurately identifying patterns. For example, who among us has never seen a familiar shape (eg, dog, cat, bird, or, my personal favourite, Snoopy) in the clouds? Of course, whatever shape you see, it is not really present in the random pattern of the clouds. To oversimplify considerably, the clouds contain enough cues that your brain is able to gather them together to produce the impression, sometimes a rather strong impression, of a familiar pattern.

Our remarkable, and quite enjoyable, ability to see patterns like these in clouds can be summarized in this way: humans have an innate ability to collect cues from random patterns and assemble them into the impression of a non-random pattern.

Two paragraphs about seeing patterns in clouds don’t amount to much, unless this habit of seeing patterns where there aren’t any occurs in our medical thinking as well as our visual processing. Unfortunately, the history of medicine is riddled with fallout from this kind of thinking, including the examples—bleeding patients and administering mercuric chloride—cited in Dr Sherman’s article.1 Whether it was drilling holes in people’s heads to relieve headaches or bleeding the remaining strength out of already-sick people, well-intentioned physicians have visited appalling, and sometimes lethal, treatments upon their patients for the simple reason that, at the time, they seemed to work.

I will omit a discussion of the other cognitive “shortcuts” that further degrade our ability to accurately discern the effectiveness of an intervention without the help of a structured trial and some statistical analysis. Unfortunately, their existence is supported by the observation that, as far as I know, many of the positive changes cited by Dr Sherman—including hand washing and decreased use of phlebotomy and hormone replacement therapy—were brought about in large part by the advent of statistical analysis in the early 1800s (I believe it seeped into medicine in the mid-to-late 1800s), allowing medical practitioners to objectively assess their time-honoured interventions. With each new piece of objective evidence, they had to adjust their thinking, and practice, accordingly.

I further assert that any intervention, complementary and alternative medicine or otherwise, that has not been proven effective in a well-designed trial remains in the same category as over zealous phlebotomy and hormone replacement therapy. That is not to say it cannot possibly be effective, but we must also consider the possibility that its use might be based entirely on the impression of a pattern that isn’t really there, just like a shape perceived in the clouds. Certainly, Sherman’s suggestion that our knowledge of physiology can be helpful in clinical decision making could be employed here, but the frequent failure of physiologically sound treatments to produce experimentally detectable benefits must be kept clearly in mind. As well, the amount of time that a belief has held sway (eg, the thousands of years that ginseng has been used) should not protect it from this consideration; I hope we can agree that people, including physicians, have a habit of seeing what they expect to see. This cognitive “habit” could be expected to insulate the assertions of respected teachers from contradictory observations in generation after generation.

In summary, then, while I agree that EBM certainly deserves considerable scepticism in its implementation, the enticing notion that the gaps in EBM can be filled with clinical judgement and common sense should receive a healthy dose of scepticism too.

(I’m sure that there are many resources that address the misleading cognitive shortcuts of the human mind. One I found very accessible and useful was How to Think Straight About Psychology.2)

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