Perfect 10s and the Odds of a Pink Nursery

Angelina Jolie and Brad Pitt, above, have a young daughter, as do Katie Holmes and Tom Cruise, below. A study found that attractive parents are 36 percent more likely to give birth to a girl than plainer couples.
Angelina Jolie and Brad Pitt, above, have a young daughter, as do Katie Holmes and Tom Cruise, below. A study found that attractive parents are 36 percent more likely to give birth to a girl than plainer couples. (By Walter Bieri -- Keystone Via Associated Press)

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By Richard Morin
Wednesday, August 2, 2006

It's no surprise to evolutionary psychologist Satoshi Kanazawa that Brad Pitt and Angelina Jolie recently gave birth to a daughter, or that Tom Cruise and Katie Holmes also are proud parents of a beautiful baby girl.

Good-looking parents are 36 percent more likely to give birth to a girl than less-attractive couples -- which also explains why women are, on average, better looking than men, argues Kanazawa, a professor at the London School of Economics and Political Science, in a forthcoming article in the Journal of Theoretical Biology.

Kanazawa based his conclusion on data collected during in-home interviews with 2,972 randomly selected young adults in 2001 and 2002. All were parents 18 to 28 years old, and they participated in the ongoing National Longitudinal Study of Adolescent Health. As part of the study, the interviewer rated the respondent's physical attractiveness on a five-point scale that ranged from "very unattractive" to "very attractive."

Kanazawa compared the percentage of boys and girls born to study participants who were very attractive with the sex ratio of babies born to everyone else. He found that 56 percent of babies born to beautiful parents were girls. For parents in each of the other categories, fewer than half of the babies -- 48 percent -- were girls.

But why are beautiful people more likely to have girls? Kanazawa says scientists studying humans and other species have found that parents who possess any heritable trait that increases male reproductive success at a greater rate than female reproductive success will have more males than female babies, and vice versa.

Because men value physical attractiveness more than women do when looking for a mate, good looks increase the reproductive success of daughters much more than that of sons. So attractive people should have more daughters -- which is exactly what Kanazawa found.

His theory also suggests that, over time, women should have become more attractive than men. These data confirmed his hunch. More than half of all women in the sample -- 52 percent -- were rated as "attractive" or "very attractive," compared with 42 percent of the men.

You Can't Choose Your Family; Neighbors, on the Other Hand . . .

An overwhelming majority of Iraqis wouldn't want an American to move in next door to them even though they are increasingly adopting American values, according to a survey in Iraq conducted earlier this year.

Nine in 10 Iraqis questioned said they would not want an American as a neighbor, up slightly from 87 percent in a 2004 survey. The surveys were conducted by researchers at the University of Michigan Institute for Social Research and Eastern Michigan University. More than 2,700 Iraqis were interviewed for the latest poll.

Iraqis also are developing a stronger sense of national identity as well as adopting values typically associated with Americans. In 2004, 27 percent strongly agreed that Iraq would be a better place if religion and politics were separated. In 2006, 41 percent expressed a similar view.

The History of Bad IdeasInflatable Hotels, Icy Warships

Last month a Russian rocket carried an inflatable space capsule into orbit, the first step in real estate billionaire Robert Bigelow's plan to create an inflatable hotel in space for adventurous tourists. We wish him well, but it reminded us of the ill-fated plan by the British during World War II to build aircraft carriers out of ice and position them to defend North Atlantic shipping lanes from German subs.

Originally the idea was to build landing strips and barracks on icebergs. Then U.S. scientists created a mixture of frozen salt water and wood pulp that was almost as strong as concrete, and the British enthusiastically changed their plans. (At one point Lord Louis Mountbatten, a supporter of the project, fired a bullet into a block of the ice-pulp mixture to demonstrate its strength. It ricocheted off the ice and struck the U.S. chief of naval operations, who was not seriously wounded.) A model was even built on Patricia Lake in Canada.

The project fell victim to spiraling costs, construction delays and the end of the war. Today, a plaque on the shores of Patricia Lake commemorates the scheme.

Who Would Have Thought?Testosterone Spikes, Drinking in College And the Dangers of Porn

· "Guns, Testosterone, and Aggression: An Experimental Test of a Mediational Hypothesis" by Jennifer Klinesmith, Tim Kasser and Francis T. McAndrew. Psychological Science, Vol. 17, No. 7. Researchers from Knox College find that male college students who held a gun rather than a child's toy for 15 minutes had elevated levels of testosterone and added three times as much hot sauce to a glass of water that another test subject subsequently had to drink.

· "Korean Working Adults' and Undergraduates' Attitudes Towards, and Self-Efficacy in, Joining Drinking Parties" by Dong Wook Lee, et al. Social Behavior and Personality, Vol. 34, No. 5. A team of Michigan State researchers and colleagues in Korea find that Korean college students drink more often than young working adults and don't feel as guilty about getting drunk.

· "Exposure to Sexually Explicit Material and Variations in Body Esteem, Genital Attitudes, and Sexual Esteem Among a Sample of Canadian Men " by Todd G. Morrison, et al. Journal of Men's Studies, Vol. 14, No. 2. A psychologist from the National University of Ireland finds that after men view porn on the Internet, they had more doubts about their own sexual performance and physical attributes.


© 2006 The Washington Post Company

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