IS YOUR DOCTOR MAKING POOR DIAGNOSTIC DECISIONS?

IS YOUR DOCTOR MAKING POOR DIAGNOSTIC DECISIONS?

Last night, Helen and I met with a friend we haven't seen for 40 years. Jay Russo and I were colleagues on the UCSD faculty, he in the psychology department and I in the economics department. We both studied decision making as viewed from the perspectives of our respective disciplines. Jay currently studies decisions made by physicians and the heuristics and biases that can lead to poor medical treatment. Remember the definition of the word heuristics as we look closely at the problem of misdiagnosis.

Heuristics: "...mental shortcuts that ease the cognitive load of making a decision."

Heuristics can be instinctive reactions, "rules of thumb", common sense, intuitive judgments, or any other expedient way of making decisions with less than complete information. Unfortunately, our tendency to allow cognitive biases to influence a decision often leads to a poor decision. Much of the time, the consequences of a poor decision are minor. When decisions are critical, such as diagnosing a medical condition, the consequences can be devastating or even fatal.

As Jay and I began our conversation, he mentioned that he had recently completed a study of 101 medical diagnoses; 86 of those decisions likely were influenced by misleading heuristics and cognitive biases. Another study in which 26 doctors verbalized the diagnostic process, only 6 clearly avoided these pitfalls.

There are literally dozens of ways heuristics can mislead and I will not list them in this brief blog. Rather I will give two illustrative examples that exemplify the problem.

1. At the height of flu season, a patient complains of difficulty breathing. The doctor listens to the chest and reviews the four primary vital signs, determines that the patient did not have an influenza vaccine, and administers the usual flu remedies. The patient eventually is diagnosed with listeria caused by eating contaminated food. The availability heuristic (not looking beyond what appears obvious) and confirmatory bias (seeking information that confirms premature conclusions rather than exploring more unlikely possibilities) unduly influenced the initial exam. The patient might have been better served if the doctor had paused, disregarded the lack of a flu vaccination, and considered alternatives.

2. A patient training for a marathon visits a sports medicine specialist complaining of a pain in his left knee. The doctor prescribes a knee brace and suggests the patient wear it while running. Months later, another doctor discovers an osteosarcoma above the left knee. The incorrect diagnosis was caused by the representativeness heuristic, an assumption that the patient is typical of other like patients. The doctor might have made a better diagnosis if she had asked herself: "would I make the same diagnosis absent the information that the patient was a marathon runner in training?" [This heuristic is responsible for many faulty criminal convictions influenced by race, gender, etc.]

Physicians can greatly improve diagnostic accuracy by following a few simple rules.

• Question the most conspicuous data; look at alternatives; 
• Occasionally assume your suspicions are wrong and entertain alternative hypotheses;
• Ask what would disprove rather than confirm your tentative conclusions.

In the above examples, there is an implication that more time and resources would be required to pursue additional options. This need not be the case; in fact there are ways to use fewer resources and incorporate the benefits of heuristics and bias avoidance. Here is an excellent example. 

It is not uncommon for an emergency patient with serious heart pain to be sent directly to the coronary care unit rather than a regular nursing bed. An alternative is to use a fast-and-frugal heuristics tree to make decisions by answering a few yes-or-no questions without knowing exact probabilities. Here is how the fast and frugal tree works.

"if a certain anomaly appears in the patient's electrocardiogram (ie, an ST-segment change), the patient is immediately sent to the coronary care unit. No other information is considered. If there is no anomaly, a second variable is taken into account, namely whether the patient's primary complaint is chest pain. If not, the patient is classified as low risk, and assigned to a regular nursing bed. Again, no additional information is considered. If the answer is yes, a third and final question is asked to classify the patient."

Substituting the fast and frugal heuristics tree for the the prior assignment criteria resulted in a much larger proportion of emergency patients with heart pain being assigned correctly to the coronary care unit thereby greatly reducing the time and resources needed to treat emergency heart patients with heart pain.

There is much promise in Jay's work (and that of his colleagues) to make significant advances improving medical care and reducing its costs. I thank him for introducing me to the subject.

Additional reading (Jay is referenced in this government publication)

How does wildlife survive wildfires?

How does wildlife survive wildfires?

Northern California is experiencing deadly firestorms as I write this blog.  I remember well October 2007 when San Diego experienced firestorms that burned hundreds of thousands of acres and destroyed thousands of homes. During every major wildfire, I worry about the families and wildlife affected by the fire. I know much about the human impact but until recently, I knew little about wildlife. In 2007 I imagined wildlife dying as flames engulfed their homes. My research since then proved my imagination partly wrong.

Kirtland's warbler thrives from wildfires

While some animals do die in fires, we forget wildfire has been a recurring natural phenomenon for longer than most species have existed on earth. Evolution has sorted out animals that can survive a large variety of environmental disruptions: summer heat turning into winter ice, hurricanes whipping up 200 mph winds, floods of fresh and salt water, periodic ice ages, and volcanic eruptions blackening the sky.

Animals have adapted to recurring natural disasters in surprisingly effective ways. According to National Geographic News, days before a tsunami hit Sri Lanka and India:
• Elephants screamed and ran for higher ground.
• Dogs refused to go outdoors.
• Flamingos abandoned their low-lying breeding areas.
• Zoo animals rushed into their shelters and refused to leave.

"Wildlife experts believe animals' more acute hearing and other senses might enable them to hear or feel the Earth's vibration, tipping them off to approaching disaster long before humans realize what's going on." (National Geographic News, January 4, 2005).

Nature has finely tuned the senses and instincts of wildlife to survive natural disasters in order to reproduce another day. In Northern California, birds fly to safety, predators enjoy a meal by catching fleeing prey but most prey escape, Amphibians burrow into the ground where conditions are survivable, and large animals like deer instinctively run to streams and lakes.

Small, young and old animals are most likely to die in a wildfire. But these are the same animals that are likely to die in the face of the many threats in their daily lives. After all, that is exactly how evolution strengthens a species over time. That is how elephants acquired the ability to predict a tsunami.

In some cases, animals have come to depend on fires to survive as a species. Kirtland's warbler is one example. These small songbirds from Michigan nest only in young jack pine forests. But the pines' cones only release their seeds in a fire. So without fire, much of the birds' nesting habitat has been eliminated. By over-controlling wildfires, we are threatening a bird species.

Santa Rosa Neighborhood yesterday

Weep not for the wildlife in Northern California, it is we humans who are most poorly equipped to to cope with Mother Nature's forces. Apparently we don't evolve as efficiently as wild species; we build homes in flood plains and fire-prone areas, we relax or circumvent building codes to reduce construction costs, we ignore or even deny that our industrial activities contribute to the climate changes which scientists predicted would cause the very events we are now experiencing, and we continue to overpopulate our planet unconstrained by natural forces. Nevertheless, people affected by fires and other natural disasters deserve out sympathy and support; they, as individuals, are not responsible for their plight, we collectively have constructed institutions and technologies that conflict with natural processes. Mother Nature will always have her way; perhaps the best we can do is console her victims and begin to make the sacrifices necessary to improve our ability to live with her in the future.

Bird Brain Part 2

Bird Brain Part 2

In my last blog, I described how some birds' brains outperform human brains. I concluded by describing some of the outstanding abilities of Alex, an African Grey Parrot. One of Alex's feats caused some confusion among my readers: I wrote that I was astounded Alex understood the concept of zero, an abstract notion that was not fully integrated into mathematics until a few hundred years ago.

The first known symbol for the number 0 

Zero plays two distinct roles in mathematics: 1) it is a placeholder, e.g., it is used to distinguish the number 1 from the number 10; and 2) it symbolizes the concept of nothingness. Indeed much confusion between these two uses of zero could have been avoided throughout history if the two distinct notions had been given different names and different symbols. Alex displayed a rudimentary understanding of zero as "nothingness" -- the absence of anything that exists.

Before proceeding, let's look more closely at how Alex processed information and how he displayed what he knew. Alex, of course, was frequently asked to perform for researchers and for the media. When Alex tired of performing, he either would say "wanna go back" [to his perch] or deliberately give incorrect answers to questions to end the session. In the case I cited in the earlier blog, Alex had become bored with performing and tried to end the session by avoiding correct answers.

"Once, Alex was given several different colored blocks (two red, three blue, and four green ...). Pepperberg asked him, "What color three?" expecting him to say blue. However, as Alex had been asked this question before, he seemed to have become bored. He answered "five!" This kept occurring until Pepperberg said "Fine, what color five?" Alex replied 'none'." (Wikipedia)
The word "none" previously had been used by Alex to say there was no difference between two identical objects.

"If asked what the difference was between two identical blue keys, Alex learned to reply, “None.” (He pronounced it “nuh.”)" In both cases, the word nuh was used by Alex to mean "nonexistence" rather than for purposes of counting. There is a long history of philosophical and mathematical controversy about zero. Indeed there are more than a dozen books devoted to the subject (my favorite is Zero, The Biography of a Dangerous Idea by Charles Seife). Unless you want to dig a little deeper into the academic side of the literature about zero, stop reading now. What follows is a simplified glimpse into the strange nature of the concept of zero and its relation to set theory from which all numbers are logically constructed. I include the discussion only because it underscores how sophisticated Alex's concept of "nuh" was.

0, 1, 2, 3... looks like a natural sequence of numbers. Zero didn't always occupy its place in this list. We saw an unintentional sleight of hand when we crossed the "Y2K" threshold on January 1, 2001, and not January 1, 2000. The reason was simply that the calendar most used by international standards were conceived when the sequence of years was numbered -2, -1, 1, 2, 3... (the negative numbers represent BC and the positive numbers represent AD). Zero was not recognized as holding its current place in the list of integers: ...-2, -1, 0, 1, 2, 3... and with good reason. Early civilizations naturally used natural numbers that could be match one for one with things (e.g., human fingers).

To be precise for current purposes, natural numbers are used to count things and begin with 1 continuing towards infinity (1, 2, 3,...,). Whole numbers are natural numbers with 0 added (0, 1, 2, 3...), Integers are whole numbers with their negative counterparts (-2, -1, 0, 1, 2, 3...).

The reason mathematics developed without zero until a few centuries ago zero was a misfit. Any natural number can be divided by another natural number but not by zero. Thus zero is a misfit, it misbehaves in other ways as well. Add a number to itself and you always get a different number (1+1=2); but not so with zero (0+0=0). Zero cannot make any number bigger; add zero to any number as many times as you like and the original number stubbornly remains the same, unlike any other number. Zero reduces any other number to zero by multiplication as if to reproduce itself indiscriminately. And there are many other anomalies that prevent zero from being a part of a simple set of rules that apply to all numbers.

Numbers can be constructed from set theory. The contents of a grocery cart is a set and its contents can be counted using whole numbers: an empty cart has zero items, I can use the express line if the set contains 15 or fewer items. But to construct numbers from set theory requires another misfit. An empty cart cannot be assigned the number zero to build numbers from sets. I will skip the technical details and ask your intuition to take a leap of faith. We must begin building numbers starting with the empty set, a set that consists of nothing. The cart contained zero items; there is a difference.

Examples of an empty set: the set containing all triangles with four corners, the set of whole numbers that are larger than 3 and less than 2. The empty set -- also called the null set -- is different than zero. A set containing zero is written as {0}. This set has one member, viz. the whole number, 0. The null set contains no members and is written {}. Alex did not declare "what color five" to be zero blocks on the tray; he said there is no group of five blocks; what color five is an empty set. That was a pretty sophisticated response for a bird brain.