What does your body say about you?
A lot, it turns out.
For example, extend your hand and compare the length of your ring and index fingers. For most women they're about the same length, and for most men, the ring finger is a bit longer.
The longer your ring finger is compared with your index finger, the more likely you are to be aggressive, athletic and prone to depression, researchers say.
Now measure the smallest finger on each hand. If they match up, you may be close to symmetrical, which is good news if you're looking for a mate. If you're not symmetrical, you, may have trouble getting a date.
OK, this isn't an exact science. But some researchers believe that body symmetry and the relative lengths of our ring and index fingers are influenced by our exposure to testosterone in the womb.
That exposure, they say, also influences a variety of personal traits. So for the past decade scientists have been measuring and comparing hands, feet, ears, limbs, joints and other body parts to see whether they provide clues to personality and behavior.
"They're an amazing kind of subtle, yet salient, cue in our development," said Randy J. Nelson, a psychology professor at Ohio State University.
Over the years, the field has generated more than 170 scientific papers identifying links, in one form or another, to athletic ability, aggressive behavior and proclivities for early heart attacks, depression and even sexual preference.
"Those with symmetrical attributes are more likely to be athletic, have lower metabolic rates, be more competitive and have higher IQs," said Gordon Gallup, a psychology professor and researcher at the State University of New York, Albany.
Some critics dismiss the field as something close to junk science. "I've always distrusted all of this, from the beginning," said Richard Palmer, an evolutionary biologist at the University of Alberta. "I don't think it's a reliable indicator of anything."
Research into finger length was initiated in the late 1990s by John T. Manning, a British researcher who was intrigued by the finding that finger length ratios are one of the few differences between the sexes that develop in the womb and are unaffected by puberty. In fact, finger length ratios remain constant throughout our lives.
"Lots of things show our sex differences, but most of them become larger or more obvious with the onset of puberty," said Manning, a researcher at the University of Central Lancashire in England. "This is one thing that doesn't."
There is no way to know the exact percentage of men or women with equally sized ring and index fingers, Manning said.
But in a 1999 report on a survey of 102 men and women, he found men with longer ring fingers scored highest in tests used to detect symptoms of depression. There was no such pattern for women.
In another survey of male heart attack victims, he found those with longer ring fingers had their heart attacks later in life.
"There are pluses and minuses to these things," he said.
But among the most consistent results are studies that link finger length to athletic abilities, Manning said. In fact, a report last week by researchers at King's College in London, which linked running ability to longer ring finger ratios in women, was one of seven studies in recent years to make such a connection, he said.
In that study, researchers found that of 607 female twins ages 25 to 79, those with ring fingers longer than their index fingers were more likely to participate in sports and compete at higher levels - particularly in sports such as soccer that involve running. Previous studies have shown the same pattern in male athletes.
At Ohio State, researchers found a link between finger length and aggression by monitoring how hard 100 male and female college students slammed down the phone when they received rude comments during what they thought was a telephone charity solicitation.
The students were more likely to slam down the phone if they had either long ring fingers or some asymmetry in their finger lengths, palm sizes, wrist diameters, elbow widths, ankle circumferences, or ear and foot sizes, the researchers said.
"It's amazing how angry people got. In interviews it came out pretty clearly," said Nelson, a co-author of the 2004 study.
Researchers in San Francisco measured the fingers of more than 700 men and women, then asked them about their sexual preferences. They found that lesbians were more likely to have ring fingers that were longer than their index fingers. There was no similar pattern among gay men, said Marc Breedlove, the Michigan State University psychologist who conducted the survey.
"I have to say, I think it is strange," said Breedlove, who published the study in the journal Nature in 2000, while he was a researcher at the University of California, Berkeley.
Breedlove, who studies the influences of sex hormones on rats, mice and hamsters, cautioned people against drawing conclusions from their own hand measurements, or those of friends. The studies are based on averages and have little meaning for any individual, he said.
"You can't tell anything definitively by the length of one person's finger," Breedlove said. "If your index finger is longer than your ring finger, don't panic."
In the studies, researchers usually measure the length of the index finger and divide it by the length of the ring finger to come up with a "digit ratio." The lower the ratio, the more pronounced whatever effect is being measured, they say.
But critics say no matter how measurements are taken, the studies are flawed and the results are questionable. Most of the research is conducted by Manning and a small number of scientists who base their conclusion on findings that are close to being statistically insignificant, Palmer said.
He added that the researchers also employ a variety of methods to take finger and body measurements, with some using X-rays and others using digital scans or direct hand measurements, he said.
"How do you measure the finger? What is the end point? It can vary depending on who is doing the measuring," Palmer said.
Manning acknowledged that some results are more reliable than others. "There's no question, there's still a lot of work to be done in the field," he said.
Researchers say that body symmetry has implications throughout the animal kingdom. Birds, rodents and other animals show a preference for symmetrical mates.
"If you can band the legs of birds with different colored bands, they will always choose the ones banded symmetrically," said Robert Trivers, a researcher at Rutgers University in New Brunswick, N.J., who has been studying symmetry and behavioral traits in 288 Jamaican children since 1996.
Humans appear to function the same way with faces that are symmetrical. The same is true in men's preference for women, Trivers said.
For body symmetry, researchers use calipers that measure limbs and joints in millimeters.
"We generally look at a number of characteristics: The length of the ears, the size of the hand, the circumference of the elbows, knees and wrists, the digit lengths," Trivers said.
But individuals can tell whether they're generally symmetrical by comparing the lengths of the little finger of each hand, Gallup said.
Most people have imperfections that throw them off their symmetry a bit - and that can actually make them more attractive in an offbeat way, experts say.
Superstar Brad Pitt comes close to being perfectly symmetrical, experts say. But actor Owen Wilson (the guy with the squashed nose in Wedding Crashers) is an example of a man with an asymmetrical face that seems to work well.
"Very few people are perfectly symmetrical. It's usually the people who are really attractive," Nelson said.