You operate the brakes, the computer controls the car and fits it into the parking space. This is now a $2,200 option, available on some Toyotas in Japan. Here is the full account. Eighty percent of the eligible customers are opting for this package. My view? If you can’t parallel park, I bet you screw up on the operation of the machine.

Mark A. Walker and John C. Wooders, economists at the University of Arizona, recently studied old videotapes of tennis matches involving stars like Bjorn Borg, Ivan Lendl and Pete Sampras. The economists looked at the serves in each match to see how well players randomly altered playing the ball to an opponent’s forehand or backhand.

Many people do poorly on similar tests when they are conducted in a laboratory. Ask somebody to write down a list of hypothetical coin-flip outcomes, for example, and the result will probably contain too few streaks of heads or tails. Because people know that the overall odds are 50-50, they underestimate how often three straight tails or four straight heads turn up.

But professional tennis players realize, on some level, that their opponent will have an advantage if he knows that a serve to the forehand is likely to be followed by one to the backhand. They do a relatively good job of mixing serves, though still not as randomly as a computer program would, Professors Walker and Wooders reported in a 2001 paper.

Controlled experiments yield similar results, read this account from The New York Times.

Here is the bottom line:

The more uncertainty that people face – be it caused by wind on a tennis court, snow on a football field or darkness on a country highway – the more they make decisions based on their subconscious memory and the less they depend on what they see.

Related research by Doru Cojoc of Clemson shows that chess players play mixed strategies to keep their opponents off balance. Furthermore they are more likely to play such sophisticated strategies, the higher the rewards on the line.

By the way, even plants seem to perform implicit calculations when they breathe, read this recent account. Armen Alchian, of course, once postulated a similar conjecture, namely that plants maximize sunlight without any conscious awareness of such a process.

Evidence is building for hormesis, the theory that suggests that moderate doses of bad things like radiation and toxins can improve health. Interestingly, much of the evidence has been around for a long time but it has been ignored because the focus was on proving the harm that toxins can cause and because low-dose effects are, by their nature, harder to identify so positive effects at low doses were typically discounted. Edward J. Calabrese of the University of Massachusetts at Amherst, however, has collected thousands of already published examples and is conducting original research of his own into hormesis. Other researchers are beginning to take notice. Hormesis is controversial, however, as you might imagine from this bombshell:

Calabrese suspects that in many cases, the benefits of hormesis may occur at levels higher than the recommended safe doses for humans.

Hormesis is a similar idea to the hygiene hypothesis (more here) which asserts that “reduced microbial exposure because of increased sanitation and cleaner lifestyles has facilitated the rise in asthma and allergic disease in the Western world.” (The mechanisms of the two effects appear quite different, however.)

Many smokers manage to smoke fewer cigarettes. The problem is that they often puff all that much harder. In the long run they may not end up much healthier, read this account. By the way, Sam Peltzman has studied this phenomenon more generally. We can do things to make people safer, but they respond by taking more risks. Thanks to Jon Klick for this latter link.

The evidence suggests that fathers prefer boys over girls. For instance a couple is more likely to stay married when they have a boy rather than a girl. Here is my earlier summary of the research.

At the same time couples are far more likely to adopt girls rather than boys? How can this be?

A recent Slate article offers some figures:

Numbers vary, but it’s pretty safe to say that somewhere between 70 percent and 90 percent of parents looking to adopt register some preference for a girl with an agency. It doesn’t matter if they’re adopting from China, where girls far outnumber boys; from Russia, where the numbers are about even; or from Cambodia, where there is typically a glut of orphan boys and a paucity of girls. Everywhere, demand tends to favor the feminine.

Steven Landsburg had suggested an adverse selection argument. Yes boys are favored but if a boy is put up for adoption, you can figure there is something wrong with the boy, for precisely that reason.

Or perhaps it is easier to nurture girls, and the nurturing motive may be central to the adoption decision. It also may be the case that mothers prefer girls and mothers also drive adoptions:

“The extent to which women are the driving force in most adoptions is probably a factor,” he says. “It’s usually true that the women are filling out the paperwork, going to the conferences, the support groups.” He adds, “If I speak at a conference–whether it’s on adoption or family issues–at least 80 to 90 percent of any of these audiences are women.”

My take: Having a boy is a riskier investment than having a girl. The risk rises dramatically with adoptions, given the associated genetic uncertainty. Males are more likely to have genetic roots for criminality and mental illness. So if you don’t know much about the parents, better to play it safe and opt for a girl.