CHICAGO -- In a sad little test of the importance of good looks, Pennsylvania scientists recently painted a large purple "birthmark" onto the face of a woman and sent her out to ride an urban subway. At a stop for Philadelphia's Temple University's emergency medical center, the woman was instructed to throw herself down on the subway car floor in an apparent epileptic seizure.
"We wanted to see how long it would take before a Good Samaritan helped her across the street," said Dr. Albert Kligman, a professor of dermatology at the University of Pennsylvania. "Instead, the car just emptied out right over her. We tried it three different times and no one ever helped her."
Of course, when her face was mark-free, help came readily.
"It pays to be good looking in this country," Dr. Kligman said during a session of the American Association of the Advancement of Science. "Appearance is so important to our opinions of other people, it's almost disgusting."
And baffling to scientists. In a weekend gathering to explore the "Science of Beauty," they expressed their astonishment at how important attractiveness is in human relationships, apparently affecting even the bonds between mothers and infants.
"When I started doing research, my goal was to show that attractiveness was not important," said Judith Langlois, a psychologist at the University of Texas in Austin. "But I've been unable to show that. Attractive individuals, adult or child, are always preferred."
Ms. Langlois has found that American standards for beauty remain remarkably consistent, almost unchanged by differences in race, education or sex.
"Eighty to 90 percent of people agree on what is beautiful," she said. "In social science, that's an absolutely astounding number."
In the 1960s, Minnesota researchers showed that good looks were the No. 1 factor in whether a person was liked or dated frequently in college, surpassing intelligence, personality and kindness. They dubbed it the "beauty is good" stereotype.
Ms. Langlois started hunting for when, exactly, that bias began. She studied 100 mothers, each with a newborn child, videotaping them as they fed or played with their infants. Consistently she found that the cuter the child, the more time the mother spent playing with it.
Infants were rated for attractiveness by independent observers, and to prove that not all babies are beautiful, Ms. Langlois showed scientists slides of newborns, some with smooth, peaceful faces, others with ragged hair and lumpy faces.
"They don't all look alike," she said. "The good news is that no mother treated her baby unkindly. The bad news is the more attractive ones got a lot more attention."
But the reverse may be also true. Ms. Langlois has videotaped 3- and 6-month-old infants looking at pictures of pretty and plain women. Consistently, the infants turn away from the plain faces and stare longer at the pretty ones. At one point, the Texas scientists hired a very pretty woman to play with babies, but on alternate days she wore a mask, designed to recast her face into knobby features.
Not only did babies look away from her when she wore the mask, they would actively try to move away from her. On the other hand, when she entered the room normally made up, the infants would stare at her and smile, and male babies, in particular, would move toward her.
She said that other studies have found similar results, although no one is sure how children so young would be able to assess attractiveness.
Allan Mazur, a sociologist at Syracuse University, pointed out that society's concepts of women's beauty have changed during the last century, particularly male judgment of what an attractive body should like like.
Mr. Mazur said that during the late 1800s, the standard requirement for chorus girls in New York City were decidedly sturdy: women about 5-feet-4 and 130 pounds.
"In the 1920s, a pear-shaped body was the ideal, with the hips being larger than the bust," Mr. Mazur said, citing movie actress Jean Harlow as a classic example.
He charted the breast, waist and hip measurements given by Playboy centerfolds from the 1960s through the mid-1980s, as an indicator of admired body shape. "Although, let's face it," he said, "those aren't necessarily the most reliable numbers."
Still, his study showed that starting about 1970, women became much taller and slighter. An analysis of the body measurements of Miss America winners showed the same thing. "There was an increasing slenderization, the ideal became much more linear," he said.
And he said that trend, like others before it, brought on some serious health problems for women. In the late 19th century, for instance, many women had their lower ribs removed, to make their waists look smaller. In the early 20th century, the ideal woman was a frail and delicate type who "needed" a man. Until the 1920s, when the flapper period made independent females fashionable, American women consumed massive amounts of drugstore medications, to emphasize their fragility,Mr. Mazur said.
"And more recently, the period of slenderization was the period of anorexia and bulimia," he said. "Now that seems to be letting up a little."
To that end, he offered one fairly frivolous clue: Playboy centerfolds have been gaining about a pound a year since 1985.