When you are a woman, a lot of the things men do are, well, hard to understand.

This weekend, tragedy struck on a mountain I had never heard of: K2 -- a 28,250-foot peak in Pakistan. Since 1939, only 280 people have reached the top of K2; more than 70 men have died trying.

Some of the latter include this weekend's rainbow coalition of 11 presumed dead: three South Koreans, two Nepalis, two Pakistanis and climbers from France, Serbia, Ireland and Norway.

An Italian, Marco Confortola, was left stranded on the mountain when helicopters could not quite reach him at 20,340 feet. Marco somehow climbed down more than 6,000 feet on black, frostbitten feet. In a satellite phone conversation with a friend, Marco said, "I never gave up in my life, I am surely not going to give up now."

I hope by the time you read this, Marco has somehow, improbably, been rescued.

Gerard McDonnell is dead. Before he died, Gerard became the first Irishman ever to reach the peak of K2. I hope it comforts his family and friends.

Why do men do these things?

I thought of Gerard and Marco while reading through a new study released by the National Bureau of Economic Research (NBER), "Gender Differences: The Role of Institutions." The authors are two women, Muriel Niederle and Alexandra Yestrumskas, who come to this conclusion: "Large gender differences in the propensity to choose challenging tasks appear to be driven by gender differences in risk aversion and in confidence about the ability to perform a new and potentially difficult task."

In the real world, discrimination or social discouragement may explain why women do not enter high-risk, high-return ventures to the same extent as men, the authors say.

In a description of this study, NBER Digest's Les Picker continues:

"However, the authors examine an environment in which women and men perform equally well, and in which issues of discrimination, or time spent on the job do not have any explanatory power." Yet under these laboratory conditions, there remain "large gender differences in the propensity to choose challenging tasks, with men choosing the hard task on average 50 percent more often than women, for any given performance level."

It reminds me of a study in 2005 by Boston University psychologists investigating why men are disproportionately victims of drowning. The answer? Men consistently overestimate their ability to swim. Continued...