Palm readers may not be the only
ones who can tell a lot about people by examining their
Recently, scientists in North America
and Europe have looked to the relative lengths of index
and ring fingers for clues about a variety of characteristics,
including musical ability, athletic prowess and, in a
study just released, osteoarthritis risk.
The researchers believe that the
difference between the two fingers' lengths signifies
the level of testosterone exposure in the womb. The longer
the ring finger compared to the index finger, the thinking
goes, the higher the exposure.
Scientists express the fingers' relative
lengths as a ratio, computed by dividing index finger
length by ring finger length. Men tend to have longer
ring fingers than index fingers, or ratios less than 1,
and women tend to have index and ring fingers of equal
length, or ratios of 1.
Don't worry if your finger ratio
looks to be more like that of the opposite sex, says Marc
Breedlove, professor of neuroscience at Michigan State
University. There's less of a sex difference in finger
ratios than there is in height, he says.
"I wish it was a better marker …
of prenatal testosterone," he says. "It's not a very good
correlation. It's easy to find women who have more masculine
ratios than some men."
Still, Breedlove says, short of a
time machine, he doesn't know of a better tool with which
to assess prenatal testosterone exposure.
Just made the connection
Giacomo Casanova, the famous womanizer
who died in 1798, observed in his memoirs that the ring
finger is longer than the index finger.
But it wasn't until 1998 that British
psychologist John Manning first linked the index-ring
finger ratio to prenatal hormone levels.
"It's been known for about a hundred
years that there's this tiny sex difference in the ratio,
but it's so small that one wouldn't think it's particularly
important," says Manning, who recently retired from the
University of Central Lancashire and is now associated
with Southampton University.
Manning had been studying whether
body asymmetry — in which, say, a finger on one
hand is longer than the same finger on the other hand
— is linked to such traits as fertility. He noticed
that in young boys, but not young girls, ring fingers
tended to be longer than index fingers. He speculated
that prenatal hormone exposure played a role.
"The sex difference almost certainly
arises before birth," Manning says, adding that it can
be seen in fetuses at nine weeks' gestation, "and it doesn't
change at puberty."
Since 1998, Manning has published
studies suggesting that male symphony orchestra musicians
have lower finger ratios than less-musical men, that heterosexual
men have lower ratios than homosexual men and that people
with lower ratios tend to do better on certain tests of
But "the links with sports are the
strongest I've found," Manning says. "They're particularly
strong with endurance running." He theorizes that prenatal
testosterone benefits the cardiovascular system.
"I think the goal is to see whether
you can find any evidence that prenatal testosterone makes
any difference at all," Breedlove says. "If you do see
a relationship between the digit ratios and whatever symptom
you're looking at, then you have to wonder."
For example, he says, "how might
prenatal testosterone influence how your joints feel when
you're 55 years old? Ten years ago, no one would have
even asked the question."
The link to osteoarthritis
British rheumatologist Michael Doherty
and his collaborators at the University of Nottingham
did just that in a study in the January issue of Arthritis
Osteoarthritis is more common in
men, Doherty says, and, he and his co-authors write, increased
activity and physically demanding sports could contribute
to the condition through repetitive joint trauma. So it
makes sense that a lower finger ratio, thought to be more
common in men and in athletic individuals, would be linked
to a higher osteoarthritis risk.
By comparing about 2,000 osteoarthritis
patients with about 1,000 people without osteoarthritis,
Doherty's team found that is indeed the case. The strongest
link: osteoarthritis of the knee in women whose ring fingers
were longer than their index fingers.
Even after accounting for such osteoarthritis
risk factors as physical activity and higher current testosterone
levels, Doherty and his co-authors found that a relatively
long ring finger was itself a risk factor. If they had
studied elite athletes, though, perhaps they would have
seen a link between physical activity and osteoarthritis
risk, Doherty says, noting, "we're just one study."
Although finger ratio is easily measured,
says Michael Peters, a psychology professor at Ontario's
University of Guelph, "I don't see it becoming a powerful
diagnostic predictor anytime soon."
But, Manning says, one country hopes
the tool will help identify future athletes. He is working
with Qatar's Aspire Sports Academy, whose vision, according
to its website, "is to discover the best young sporting
talent … and transform them into world-renowned
Manning's goal: to prove that finger
ratio at age 10 predicts athletic ability at age 18.