he Illusions of Lane-Switchers

You're stuck in bumper-to-bumper traffic. The next lane seems to be moving a bit faster. So you wait for your opportunity, and quickly change lanes. Everything stops and the car that was behind you in the other lane inches past. Why?

A pair of researchers thinks they have the answer: It's an illusion.

Donald A. Redelmeier of the University of Toronto and Robert J. Tibshirani of Stanford University created computer simulations of congested traffic and videotapes of real traffic tie-ups to test drivers' perceptions.

"From these results, we suggest that drivers are responding to an illusion: namely, that the next lane on a congested road appears to be moving faster than the driver's present lane, even when both lanes have the same average speed," they write in the Sept. 2 issue of Nature.

Vehicles tend to "spread out when moving quickly and pack together when moving slowly. A driver can therefore overtake many vehicles in a brief time interval, but it takes much longer for the driver to be overtaken by the same vehicles," they write.

In addition, "vehicles that are overtaken become invisible very quickly, whereas vehicles that overtake the index driver remain conspicuous for much longer. Moreover, a driver is more likely to glance at the next lane for comparison when he is relatively idle while moving slowly," the researchers write.

From Humble Roots, Fine Wines

Some of the finest wines have surprisingly humble roots.

A team of researchers from the United States and France used DNA fingerprinting to study the parentage of some 300 varieties of grapes from northeastern France. To their surprise, the researchers found that 16 varieties, including chardonnay, gamay noir, Aligote and Melon, are the offspring of pinot and Gouais grapes.

While pinot is considered a premium grape, Gouais blanc is considered so mediocre that there were several unsuccessful attempts in the Middle Ages to ban it and they are no longer planted in France. "The name 'Gouais' derives from the old French adjective 'gou,' a term of derision," the researchers write in the Sept. 3 issue of Science.

Wear Your Mittens, Sleep Well

Rather than a warm glass of milk or counting sheep, wearing socks and mittens to bed may be a good way to fall asleep.

Anna Wirz-Justice of the Psychiatric University Clinic in Basel, Switzerland, and colleagues studied 18 healthy young men, carefully monitoring the temperature of various parts of their bodies. Those with warm hands and feet were most likely to fall asleep easily.

"Here we show that the degree of dilation of blood vessels in the skin of the hands and feet, which increases heat loss at these extremities, is the best physiological predictor for the rapid onset of sleep," the researchers write in the Sept. 2 issue of Nature.

Dilating blood vessels in the extremities helps redistribute body heat, which appears linked with the release of hormones, such as melatonin, that are involved in making people feel sleepy, the researchers say.

Is It a Boy or a Girl?

Folklore is filled with ways a pregnant woman can supposedly predict whether she's having a boy or a girl. If she's carrying the baby high, it'll be a boy. If a needle hung from a string over her belly swings in a circle, it's a girl.

To test these methods, Deborah F. Perry of Johns Hopkins School of Public Health and colleagues asked 104 pregnant women to use whatever approach they wanted--dreams, hunches etc.--to guess the sex of their babies. Overall, the women predicted the gender correctly 55 percent of the time, which is no better than mere luck.

Women with more than 12 years of education were right 71 percent of the time, while those with only a high school education were correct only 43 percent of the time--a surprising finding the researchers could not explain.

"We can offer one speculation concerning a group difference in subjects' interpretation of the main question regarding fetal sex," the researchers write in the September issue of the journal Birth. "Women in the less educated group seemed more likely to answer that they thought they were having one sex over the other because they preferred one sex, without giving the issue the same degree of evaluation present in the more highly educated group."

CAPTION: "Gouais blanc" grapes, no longer planted in France.