Sunday, June 20, 2021

How Physicians Think

One of the more interesting aspects of my career has been contemplating how physicians make decisions on both the diagnostic and therapeutic side. Early in my career there was an explosion of activity in this area. Much of it had to do with internal medicine. There were computerized programs that were designed to assist physician decision-making. There were also entire courses taught at the CME level by experts in the field. At the time those experts included Jerome Kassirer, Stephen Pauker, Harold Sox, Richard Kopelman, Alvan Feinstein, and others.  The New England Journal of Medicine has a long-standing feature entitled Case Records of the Massachusetts General Hospital that showcases both diagnostic reasoning and the associated clinicopathological correlates. They added additional articles and a long standing feature on diagnostic decision making. After studying the subject area for about 10 years, I started to teach my own version to 3rd and 4th year medical students. It was focused on not mistaking a medical disorder for a psychiatric one.  It included a complete review of cognitive errors in that setting and how to prevent them. I taught that course for about 10 years.

There are a lot of ideas about psychiatrists and how they may or may not diagnose and treat medical disorders. Systematic biases affect the administrative and environmental systems where psychiatrists work.  Many psychiatrists are very comfortable at the interface of internal medicine or neurology and psychiatry. The most common bias about psychiatrists is that other medical conditions need to be “ruled out” before the patient is referred to a psychiatrist. From a psychiatric perspective the real day-to-day problems include inadequate assessment due to an inability to communicate with the patient and considerable medical comorbidity. Psychiatrists who work in those problem areas need to be competent in recognizing new medical diagnoses and making sure that their prescribed treatment does not adversely affect a person with pre-existing medical disorder.

Against that backdrop I decided to read 2 relatively new books. Both of them have the same title “How Doctors Think”. One book was written by Jerome Groopman, MD hematologist-oncologist by clinical specialty. The other book is written by Kathyrn Montgomery, PhD – a professor of Bioethics, Humanities, and Medicine. As might be expected from the writers’ qualifications Groopman is writing more from the standard perspective of a physician with an intense interest in medical decision making and Montgomery is describing the clinical process and analyzing it from the unique perspective of philosophy and the humanities. It follows that even though the titles are the same these are two very different books.

Groopman’s approach is to use a case-based style of looking at medical decision-making from the perspective of several clinicians-including his own work. The mistakes that occur are teaching moments and are explained from the perspective of heuristics or common cognitive biases. It is the approach I used in my course on preventing cognitive errors associated with psychiatric diagnoses. To cite one example, he describes an athletic forest ranger in his forties. The kind of a guy an internist might say: “I am not worried about his heart – he does his own stress test every day.”  He noticed increasing chest discomfort for a few days without any associated cardiopulmonary symptoms. He presented for an assessment on a day when the pain did not go away. He was seen and thoroughly examined.  There were no physical symptoms, exam findings, or laboratory finding to suggest a cardiac problem and he was released from the emergency department.  He returned a few days later with a myocardial infarction.  Discussions with the attending physician indicate that there were two issues associated with the missed diagnosis of cardiac chest pain – the generally healthy appearance of the patient and a lack of any positive tests indicating coronary artery disease.  Groopman discusses it from the perspective of representativeness bias (p 44) or being affected by a prototype – in this case the patient’s apparent level of fitness and attributing the chest pain to musculoskeletal pain rather than pain of cardiac origin. 

This case also allowed for a discussion of attribution errors especially if the patient fits a negative stereotype.  In the next case, a 70 yr old patient with alcohol use presents with and enlarged nodular liver on exam.  The presumptive diagnosis is alcoholic cirrhosis and the team’s plan was to discharge him back home as soon as possible. Closer examination confirmed that the patient was not drinking that much and searching for other causes of liver disease resulted in a diagnosis of Wilson’s disease.  For most of the book, Groopman uses this technique to illustrate substantial errors, the kind of cognitive bias that it reflects, and corrective action. The reality of “making mistakes on living people” comes though.

He recognized the importance of pattern matching and pattern recognition in clinical practice. There is an initial conversation with a physician that collapses pattern recognition to stereotypes and their associated shortcomings.  He elaborates on the concept and quotes a cognitive scientist to illustrate that pattern recognition may not require any conscious reasoning at all.  An expert can arrive at a diagnosis in about 20 seconds that may take a medical student or resident 30 minutes. Experts begin collecting information about the patient on contact and are immediately considering diagnostic possibilities. I have personally had this experience many times, typically for acute neurological syndromes (strokes, cerebral edema, encephalitis, meningitis) in patients who were referred for me to see in a hospital setting. Pattern matching clearly occurs in the diagnostic process, but it is more difficult to write about and discuss than verbal reasoning.

A major strength of the book is a fairly detailed look at uncertainty in medicine. The diagnoses are not etched in stone and no outcomes are guaranteed based on the accuracy of the diagnosis or not. He introduces a pediatric cardiologist who advances the argument that most of his cases are novel and that there are no set guidelines for what he treats. Even more complicated is that fact that what may appear to be sound science-based treatments like closing an atrial septal defect with a 2:1 shunt in kids it can be an illusion.  Many of those children do well without the surgery and many have had unnecessary surgery. The cardiologist also points out that study of this kind of problem is impossible because of the length of time it would take to do a randomized study.

Another major strength is advice to patients about how to keep the doctor they are seeing thinking about their case.  Numerous examples are given ranging from seeing large number of healthy patients where abnormalities are rare to seeing patients with real problems who have been stereotyped for one reason or another. Groopman is very specific in coaching prospective patients in how to overcome some of the associated biases.  This advice centers on the fact that biological systems are complex and don’t necessarily support logical deductions.  The astute doctor needs to be systematic, evaluate the data for themselves including the elicitation or more history, and question their first impressions. The patient aware of these limitations can ask the correct questions along the way to assist their physician in staying on track. He advises the patient to express their concern about the worst-case scenario to get that out there for discussion and to keep their doctor focused.  The patient is informed of how their history, review of systems and exam may need to be repeated along with some tests that have been previously done. The physician may have to ignore common aphorisms or maxims that are designed to focus on common problems and consider the complex – like more than one diagnosis being suggested. Business management of the medical encounter is seen to impair and obstruct this interactive process.

Groopman’s book is very good both as a guide to patients and a review for physicians who have been educated in diagnostic thinking. In the body of the book technical jargon is avoided and the case scenarios thoroughly explained. There is an excellent list of references and annotations for each chapter at the end of the book. 

How Doctors Think by Kathryn Montgomery takes the unexpected form of a philosophical argument against medicine as a science. She qualifies her criticism by being very clear that she is considering Newtonian or positivist science and not biological science. She recognizes several features of biological science that make it an integral part of medicine, but also not at all like the criteria for science that she sets as the premise for her argument. This is problematic at two levels. First, deterministic and reductionist physicists like Sabine Hossenfelder are very clear that everything is reducible to known subatomic particles and that particles in a brain are deterministic.

“Biology can be reduced to chemistry, chemistry can be reduced to atomic physics, and atoms are made of elementary particles like electrons, quarks, and gluons.” (5)

So for at least some scientists – reductionism is not a problem and the boundaries are not very clear between physical science, biology, and medicine.  Second, it is now known that biological organisms have a wide array of stochastic mechanisms that by virtue of their own nature produce apparently random results. With that range of possibilities, it is not very clear if the standards of physical science are that much different than the biological science necessary for medicine.

Montgomery makes the argument about science and the damage that the idea of medicine as science does to both medicine and its practitioners at several levels.  First, she describes science in medical training. Medical students encounter the basic science curriculum in the first two years of medical school. It is not physical science but biological sciences relevant to understanding pathophysiology, pharmacology, and epidemiology/evidence-based medicine.  She suggests this exposure to science is less relevant as the student transitions to a clinician with adequate clinical judgment – almost to the point that the basic science is an afterthought. This aspect of training is also used to point out that medical students are not being trained as scientists and the remainder of their formal education is spent learning clinical judgement.  At places she describes the preclinical years as fairly bleak period of memorization peripherally related to clinical development.  Second, the uncertainty of biology and medicine is part of her argument.  She extends the argument from the patient side to the side of the doctor. Patients want and need certainty and therefore they want doctors who are schooled in the best possible science who can provide it. Patients want an answer and all they get is statistics. Third, she suggests that the moral and habitual practice of medicine although dependent on human biology and the associated technical advances is not really science.  Physicians are taught to practice medicine and the don’t question “the status of its knowledge” (p. 191). She describes medical practice as a set of rational procedures that are shared with many other professions in the humanities and social sciences.  Fourth, the notion of medicine as a science is “clinically useful” in that it reassures the patients that physicians are engaged in a rational process like they were taught in science classes rather than a contextual, interpretive, narrative process used by non-scientists.  She cites numerous examples of maxims and aphorisms used in medicine to guide this process like Peabody’s famous: “The secret of the care of the patient is in caring for the patient.” 

 Montgomery’s writing is as sophisticated as you might expect from a bioethics professor with a doctorate in English and extensive exposure to medical training. Her critique depends a lot on verbal reasoning and the application of that model to numerous disciplines. Philosophical critiques of medicine and psychiatry that I have responded to in the past are typically presented as arguments with the premises being set by the author. As I read through these arguments being repeated across chapters there were clear points of disagreement.  Here is a short list:

1:  The argument about medicine not being a physical science – that is a good starting point if you want to be able to attack the scientific aspects of medicine, but does anyone really accept that premise? No physical science is taught in the basic science years of medicine.  The basic sciences are focused on human anatomy and physiology. An associated argument is that biological sciences have no overriding laws like physics and that is given as further evidence that medicine is not a science. There is an entire range of science within the basic science of medicine that cannot be explained by physical science but it is necessary for clinical medicine and innovation in medicine.  Finally science is a process that is subject to ongoing verification. That is as true for biological science as it is for physical sciences. While there appear to not be as many absolutes for biology progress is undeniable even within the boundaries of medicine.

2:  Uncertainty in biological systems and medicine - the author makes it seem like defining medicine as a science gives the false impression of certainty. I don’t think that certainty is misrepresented or minimized in clinical medicine.  Every physician I know experiences the uncertainty during informed consent and prognosis discussions. It is built into surgical consent forms and in situations involving medical treatment or testing – the discussions are even more complex. In a typical day, I will advise patients on side effects that occur at rates varying from 4 out of 10 patients to 1 out of 50,000 and tell them what to look for and when to call me.  I have had patients tell me after those discussions that they would prefer not to take a medication or do the recommended testing. I will also discuss life threatening problems with patients, and let them know I cannot predict outcomes but can advise them on how to reduce risk. The only way medicine can practiced is by having appropriate informed consent discussions that fully acknowledge uncertainty and the associated biological heterogeneity.  From the patient side, everyone has a friend, acquaintance, or family member who was healthy until the day there were not. The uncertainty of physical health and medical outcomes at that point are widely known by the general public.

An additional and lesser known aspect of the effect of uncertainty on physician behavior is encouraging the correct answer or treatment as soon as possible. Montgomery attributes some of this to the moral dimension of the physician-patient relationship and doing the right thing for the patient.  But a critical part of uncertainty is that physicians eventually learn to project their decisions out into the future. Those projections are all taken into account in developing the current treatment plan. The outcome of an idealized plan can be viewed as the direct result of the uncertainties involved.  

3:  Physician detachment is a likely consequence of characterizing medicine as a science – At points Montgomery makes the point that physician can emotionally protect themselves by assuming the detached rationality of science. It follows that abandoning medicine as a science would result in a more realistic emotional connection with patients. She has a detailed discussion of the physician-patient relationship being more as a friend or a neighbor.  She concludes that neighborliness has a number of virtues to recommend it as the relationship for the 21st century. Two concepts from psychiatry are omitted from this discussion – empathy and boundaries. Empathy is a technical skill that is typically taught to physicians in their first interviewing courses in the first year of medical school.  It is a technical skill that allows for a more complete understanding of the patient’s emotional and cognitive predicament. In my experience what patients are looking for is a physician who understands them. That is generally not available from a friend or neighbor.  The basic boundary issue is that it is very difficult to provide care to a person who is emotionally involved with the physician. There are degrees of involvement, but any degree is important. A physician who is empathic, had a clear awareness of the relevant boundaries, and has a solid alliance with the patient is far from detached.  But I would not see them as neighborly or a friend.  The physicians job is the be in a position where they can provide the best possible medical advice. That can only happens from a neutral position where they can give a patient the same advice they would give anybody else.  That also does not mean that physicians are not emotionally affect when bad things happen to their patients or when their patients die.

4:  Do ancient Greek concepts still apply? – The author uses Aristotelian definitions of episteme and phronesis several times throughout the text. Episteme is scientific reasoning and phronesis is practical reasoning.  Aristotle’s view was that since there are no “fixed and invariable answers” to questions about health, every question must be considered an individual case.  In those cases, practical reasoning that considers context and additional factors or phronesis applies.  That allows the author to compare medicine to a number of social science disciplines that use the same kind of reasoning.  The question needs to be asked: “What would Aristotle conclude today?”  In ancient Greece there were basically no good medical treatments and medical theory was extremely primitive. Over the intervening centuries medicine has become a lot less imperfect. Uncertainty clearly exists, but the scientific advances are undeniable.  It is possible to say today that there are now fixed and invariable answers to large populations of people. Medicine has always been a collection of probability statements – but those probabilities in terms of successful outcomes have significantly improved.  One the corollaries of  Aristotle’s work is that there can be “no science of individuals” and yet the current goal is individualized or personalized medicine.

5:  Is science relevant to clinicians on a day-to-day basis? -  I think that it is.  I have certainly spent hours and even entire weekends researching patient related problems to find the best solution to a problem and to be absolutely sure that my recommended course of treatment would not harm the patient. All of that reading was basic or clinical science.  On the same day that I received Montgomery’s book, I got my weekly copy of the New England Journal of Medicine.  I have been a subscriber since my first year of medical school based on the recommendation of my biochemistry professor. Our biochemistry class was designed around research seminars where we read and critiqued basic science research. There was also the assumption that you were reading the text cover to cover and attending all of the lectures.  He encouraged all of us to keep up on the science of medicine by continuing to read the NEJM and in retrospect it was a great idea.  In that edition I turned to the Case records of the MGH (6): An 81-Year-Old Man with Cough, Fever, and Shortness of Breath. It was a detailed discussion by an Internist about the presentation and differential diagnosis of the problem. And there on page 2336 was a diagram of the ventilation perfusion mismatch that occurs with a pulmonary embolism and acute respiratory distress syndrome. I have seen this science at the bedside in many clinical settings.  

The clinical competency of pattern matching, pattern recognition, and pattern completion is left out of Montgomery’s description of how doctors think and it is an important omission.  It is a good example of non-verbal and unconscious reasoning that can be a critical part of the process. The answer to the question: “Is this patient critically ill?” and the triage that follows depends on it.  Pattern matching is also experience dependent with experts in their respective fields being able to more rapidly diagnose and classify problems that physicians who are not experts. Biases affecting verbal reasoning can negatively impact the diagnostic process, but so can the lack of experience in seeing patterns of illness and an inadequate number of cases in a particular specialty.

I consider both of these books to be good reads, especially if you are a physician and have had no exposure to thinking about the diagnostic process.  Both authors have their own ideas about what occurs and there is a lot of overlap. Both authors have the goal of stimulating discussion and analysis of how physicians think and educating the general public about it. Physicians will probably find Groopman a faster and more relatable text. Physicians may find the references and vocabulary used in Montgomery to be less recognizable. I would encourage any physician who is responding to initiatives to change the medical curriculum or critique it to read Montgomery’s book and work through her criticisms.  Both books have excellent references and annotations listed by the chapter for further reading. Non-physicians especially patients who are working with physicians on difficult problems may benefit from Groopman’s tips on how to keep those conversations focused and relevant.  As a psychiatrist who is sensitive to attacks (even philosophical ones) from many places – you may find my criticism of Montgomery’s work to be too rigorous. I tried to keep that criticism down to a level that could be contained in a blog post.  I encourage a reading of her book and formulating your own opinions. It is an excellent scholarly work.

Finally, the area of expertise in medicine and the associated clinical judgment of experts is still a current research topic.  The research has gone from basic experiments about who can properly diagnose a rash or diabetic retinopathy to a clear look at brain systems responding during that process. Those changes have occurred over the past 30 years. At the descriptive level it remains important to be aware of the possible cognitive biases and what can be done to overcome them.


George Dawson, MD, DFAPA



1:  Groopman J.  How Doctors Think. Houghton Mifflin Company, New York, 2008.

2:  Montgomery K.  How Doctors Think. Oxford University Press, New York, 2006.

3:  Kassirer JP, Kopelman RI.  Learning Clinical Reasoning. Williams and Wilkens, Baltimore, 1991.

4:  Sox HC, Blat MA, Higgins MC, Marton KI.  Medical Decision Making. Butterworths, Boston, 1988.

5:  Hossenfelder S.  The End of Reductionism Could Be Nigh. Or Not.  Nautilus June 18,2021 (accessed on June 18, 2021)

6:  Hibbert KA, Goiffon RJ, Fogerty AE. Case 18-2021: An 81-Year-Old Man with Cough, Fever, and Shortness of Breath. N Engl J Med. 2021 Jun 17;384(24):2332-2340. doi: 10.1056/NEJMcpc2100283. PMID: 34133863.


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