A friend of mine was ventilating the other day. She was angry that a doctor, a specialist, waved off her upset stomach without much more than a cursory examination and a prescription for antacids.

"You know how long he took to look at me," she asked?

"Eighteen seconds," I said. I knew that from an interview I'd heard with the renowned doctor and writer, Jerome Groopman. Eighteen seconds is apparently all the time it takes for most doctors to make up their minds.

Groopman is the author of How Doctors Think and a specialist in the field of experimental medicine. He also teaches at Harvard Medical School and is a staff writer at the New Yorker (he's a busy man, indeed).

His message is that, in many ways, doctors don't think that differently than the rest of us. It's just that what they think has more consequences.

When you make an error, does anyone die? Not usually, unless you're driving and do something stupid or, perhaps, if you are an air traffic controller with a planeload of lives in your hands.

But if a doctor makes the wrong diagnosis, it is usually someone else — you the patient — who lives with the result.

The error factor

Groopman tells us that doctors' mistakes have been well studied and that, most of the time anyway, physicians get it right. In fact they get it right, four out of five times.

Turn that positive news around, though, and it means that doctors misdiagnose patients 20 per cent of the time, which Groopman feels is a conservative number.

It gets worse. About half of that 20 per cent will suffer serious consequences as a result of medical error.

That means patients are misdiagnosed roughly 10 per cent of the time they visit a doctor.

Can you think of anyone you know who would fit this seemingly small but plentiful number? I think probably everybody can.

My doctors didn't catch my brain tumour for years. Groopman himself had two episodes of misdiagnosis, for a painful hand and a back condition. And he's a Harvard doctor!

I would have thought doctors received special treatment. But the more attention Groopman sought and the more specialists he saw, the more opportunities for his misdiagnoses to multiply like viruses.

Groopman is a doctor, so he's also seen this phenomenon from the other side of the stethoscope. Sadly, he too has misdiagnosed patients.

When he was a resident, a woman came to see him with a pain in her chest. He dispatched her quickly with a prescription for antacids. Two weeks later she was dead from a hole in her aorta, the main artery carrying blood from the heart.

He missed it. He still hasn't forgiven himself.

Diagnosis momentum

Antacids seem to be a favourite medicine for doctors who want to hurry you along. And it's probably true that 80 per cent of the time when there is a problem, stomach acid is at fault.

Groopman handed out a prescription to his patient. My friend received her script after a cursory inspection.

My father was sent off with antacids after he visited an emergency room, complaining of chest pain. He died later that morning of a heart attack.

So what's going on here? Are doctors simply too busy? Sloppy? Irritated? Groopman tells us that doctors are especially prone to misdiagnose patients if they don't like them.

The real problem, though, he says, is that doctors, like all human beings, are caught up with what's called anchoring.

That's what happens when data floods our minds like a blizzard and our brains erect filters to sort and guide what we're processing.

What often happens in these cases is that when the mind seizes on one explanation, it quickly interprets all evidence that way.

That's why first impressions are so important: The mind simply freezes up around them.

Put four doctors in a room, says Groopman, and what you can end up with is a case of "diagnosis momentum." During every episode of the TV series House, this probably happens a dozen times.

Doctors and jihadists

Medicine, we are constantly told, is a notoriously tricky enterprise, a combination of science, guesswork and diagnostic art.

Doctors, as with so many other people, dislike ambiguity. They can rush to a solution to end the mental discomfort of not really knowing what's going on.

Very good (and humble) doctors try to avoid the problem of anchoring by learning to become comfortable with uncertainty, often against the wishes of their colleagues and patients.

But doctors are not the only people anxious about uncertainty.

Recently, the National Post ran a lead editorial that asked: Why do so many Islamic jihadists and suicide bombers come from technical fields such as engineering.

Eight of the 25 known participants in the Sept. 11 plot had engineering backgrounds. Mohammed Atta, a ringleader, was an architectural engineer.

The Post cites a working paper by the Oxford sociologists Diego Gambetta and Steffen Herzog, who study Islamist movements.

According to them, almost 7 in 10 violent Islamists were educated men. In one study of "educated fanatics," says the Post, "a whopping 78 had studied engineering."

The sociologists suggest that engineering, with its exacting, precise nature, provides a comforting mindset for potentially violent radicals. As with technical specialties that resist uncertainty, rigid, fundamentalist thinking can act as an anchor for jihadists.

Probably that is why we have never heard of any suicide bombers who were cosmologists or string theorists.

With all the theoretical playfulness of these fields — the models of baby universes and multiple dimensions — you must live with uncertainty in the very way you think about the world.

There are no right or wrong answers in these specialties, only hypotheses.

But surely, you say, medicine shouldn't be an inexact science like cosmology. Yes, but the uncertainty in medicine isn't because of its theoretical nature, it is because the true cause of an illness can be maddeningly elusive.

That is why Groopman advises that when you see a doctor and get a diagnosis, you should ask two things: "What else could it be?" And, "could it be two things at the same time?"

Doctors are not trained to think like that. They like one economical answer.

Complexity and ambiguity are mentally uncomfortable. People try to avoid them. But when it comes to doctors, the lesson should be: Don't be satisfied with their easy authority.

Faced with a tricky health problem, get your doctor to pull up his or her anchor and not rush to judgment. When it comes to dealing with religious fanatics, mind you, we've all got our work cut out for us.