29 Sep 2011


Throughout our school years, our teachers keep asking us to be humble. In medical school, we are taught not to jump to conclusions. We should always consider differential diagnoses and perform more confirmatory tests.

Have we followed their advice? Is the advice sound?

Let’s consider the second question first. In the last issue of Nature, Dominic Johnson and James Fowler used an evolutionary model to show that overconfidence confers survival advantage. [Nature 2011;477:317-20] When more than one person competes for resources, the decision to fight depends on the chance of winning as well as the cost of losing. If each person has perfect knowledge on the strength of oneself and the other competitors, the decision is straightforward. You only claim the resources when you are stronger than others, and should not fight at all in face of a stronger opponent.

In reality, however, perfect knowledge is rare. The decision is therefore based on an estimation of one’s strength in relation to others. As a result, a person who overestimates his strength would fight more often than average, while one who underestimates oneself would more likely give up. According to Johnson’s and Fowler’s model, overconfident populations would claim more resources in most situations and gradually grow in strength. The only exception is when the cost of losing is particularly harsh. For example, when KL was a senior medical officer, you would be a fool to argue with him about call duties. First, you still lose the argument. Second, he gives you an extra call next month.

No wonder we see so many arrogant people around. Now that we understand how they evolved, we should no longer hate them but congratulate them for improving our species. In an accompanying commentary, van Veelen and Nowak named a number of real life examples. [Nature 2011;477:282-3]

"Most people report their driving abilities to be above average. 70 percent of high school students think their academic performance is above average. 94 percent of professors rate their teaching abilities as above average."

I can easily add more items to the list. 100 percent of endoscopists underestimate their average cecal intubation time. 95 percent also overestimate the size of peptic ulcers they treated and polyps they removed. Don’t be surprised if you read an endoscopy report saying there was a 5 cm ulcer in the narrow first part of duodenum.

That is why we are so competitive.

22 Sep 2011


A recent meta-analysis confirmed the “July effect”. [Young et al. Ann Intern Med 2011;155-309-15] During changeover to a new group of interns, mortality of in-patients increases by 4-12%. This is accompanied by an increase in medical errors and prolongation of hospital stay.

It is often a relief to note that terrible things do not occur only locally. On the other hand, the fact that “July effect” is genuine and widespread is disconcerting. If a disease is causing deaths of this magnitude, it would have drawn a lot of attention. New treatments would be developed and introduced every year. The same does not apply to human errors. Professionals tend to accept that it is natural and inevitable that newcomers would commit errors.

While I was pondering this question, KM joined us for lunch. “I have a new proposal,” he announced. “Let’s ask interns to take care of all emergency cases. To ensure compliance, we can assign whole day clinics to on-call medical officers. The cases would then be reviewed only by the physicians in the evening.”

LS was speechless. After a while, the intern coordinator finally said, “But our patients will die!”

“Interns are supposed to see emergency cases now,” reminded my mentor. “Why do we have to change?”

“I was approached by an intern,” KM explained. “She wished to see emergency cases, but said she could only do so if we put it as a policy.”

“Why?” all of us asked. “If she is eager to see the cases, who would stop her?”

15 Sep 2011



“As a leader, one hears rumors about his staff from time to time. If you were the King of Zhao, how would you handle the situation?” asked my mentor one day.

My mentor rarely talks about Chinese history, so I knew it must be important. “With hindsight,” I answered, “sacking the general would of course be the worst option. I suppose I would not do anything.”

“If you have known your staff for years, you should understand his temperament and not be affected by rumors easily. Having said that, keeping silent is not good enough. Your staff is not stupid. He must have heard the rumor, too. If you do nothing, he would think you are plotting something. In this situation, I would tell the general that I heard some rumors but I believe in him.”

8 Sep 2011


Angelina began her life as a primary school student last Friday. To celebrate this important event, parents prepare all sorts of gifts for their children. Some may choose books, others toys, or even stocks. We did something different. The answer can be found at www.ahwwong.blogspot.com.

1 Sep 2011


“You have been on Szeto’s blog for 5 consecutive days!” exclaimed LL and HC.

They were talking about my post 3 weeks ago (http://vwswong.blogspot.com/2011/08/unlucky.html). That piece was written for fun, but the subsequent elaboration by my friend was a masterpiece. As a result, there was also a modest increase in the number of views on my blog.

If that was a scientific article, it would have become a highly-cited paper. After impact factor, universities worldwide are now obsessed about citations. This is a fairer way to evaluate scientific works. After all, impact factor was designed to measure the performance of journals but not individual papers (see http://vwswong.blogspot.com/2011/01/impact.html for details). Individual papers are better judged by how often they get cited by others and whether they stimulate further works in related fields.

Nevertheless, my example illustrates that this system is imperfect. True, landmark studies and major breakthroughs are highly cited. But so are controversial and flawed works. Others cannot help refuting a shaky article. At the same time, however, they are forced to cite the original work.

P.S. Yes, I do look at my blog statistics because it is so interesting. At one time, I could not understand why so many Russians were reading my scribbles. LL enlightened me. That happened because similar blogs were blocked by the Chinese government. The ‘Russians’ were actually friends from mainland China (I forgot the technical term describing this phenomenon). Anyhow, I cannot be more grateful.