The changing of the mind

David Buss has spent his career exploring Freud's cosmic riddle: What do women want?

When it came to sex, Buss, a University of Texas psychologist, always believed that women pursued two basic strategies, depending on whether they wanted short-term or long-term relationships. Like many men, he grossly underestimated their complexity.

Turns out that women have "34 distinct strategies for promoting short-term sexual encounters and double that number for attracting a long-term romantic partner," Buss says.

Women have 19 strategies for keeping their partners and 29 ways of getting rid of them -- including sleeping with them. And that, Buss adds, is just one of the 280 reasons researchers have identified for why women have sex, among them "to get rid of a headache," "to get closer to God," "to become emotionally connected to my partner" and "to get my boyfriend to shut up."

Buss' acknowledgment of his error seems startling at a time when people would rather stick ice picks in their eyes than admit they have made a mistake.

And that's the genius of the 11th annual Edge Question posed to 163 scientists and science writers: "What have you changed your mind about?"

As in the past, these world-class thinkers have responded to Web site editor John Brockman's impossibly open-ended questions with erudition, imagination and clarity.

In explaining why they have cast aside old assumptions, the respondents' short essays tackle an array of subjects, including the nature of consciousness, the existence of the soul, the course of evolution and whether reason will ultimately triumph over superstition.

One of the most fascinating admissions comes from the Danish science writer Tor Nørretranders, who says he believes in "permanent reincarnation." He doesn't mean life after death but the little-understood process whereby our bodies are reborn every moment of every day.

"A chair or a table is stable," he observes, "because the atoms stay where they are." But 98 percent of the atoms in our bodies are replaced every year, and almost no atoms stay with us from cradle to grave. "An average person takes in 1.5 ton of matter ever year as food, drinks and oxygen. All this matter has to learn to be you. ..." Thus, "We reincarnate ourselves all the time."

Neurobiologist Leo Chalupa says the constant renewal of neurons in the brain presents "a real puzzle to ponder" when we consider our sense of self. If "[y]our brain is different than the one you had a year or even a month ago," he asks, "... how is the constancy of one's persona maintained?"

Two of the most interesting answers may signal a cease-fire in the gender wars.

In 2005, Harvard President Lawrence *. Summers was assailed for suggesting that innate differences might explain why there are few top women scientists. Now Diane F. Halpern, a psychology professor at Claremont Mc-Kenna College and a self-described "feminist," says Summers was onto something.

"There are real, and in some cases sizable, sex differences with respect to cognitive abilities," she writes.

Her views are echoed by Helena Cronin, a philosopher at the London School of Economics.

"Females," she writes, "are much of a muchness, clustering around the mean." With men, "the variance -- the difference between the most and the least, the best and the worst -- can be vast." Translation: There may be fewer female geniuses in certain fields, but there are also fewer female morons.

The few respondents who mentioned today's most prominent scientific issue -- global climate change -- spoke with a single voice of fear: "The sea ice of the Arctic is melting far faster than anyone had predicted," writes Steve Connor, science editor of The Independent in London, "and the record minimum seen in summer 2007 (which followed the previous record minimum of 2005) has shocked even the most seasoned Arctic observers."