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Author Topic: finger length  (Read 9313 times)

paul.fr

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finger length
« on: 20/04/2007 02:38:41 »
why are our fingers different lengths? does the middle finger being longer serve a purpose?


 

another_someone

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finger length
« Reply #1 on: 20/04/2007 02:58:36 »
http://psychologytoday.com/articles/pto-3791.html
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Look down at your right hand. Is your ring finger longer than your index finger? Or vice versa? To be certain, take a ruler and measure from the bottom crease of each finger to the tip.

The measurements tell you something about the environment of your mother's womb just weeks after your conception, a time when your fingers, and more importantly, your brain, were developing. Because of the influx of sex hormones at this prenatal stage, men tend to have ring fingers that are slightly longer than their index fingers. In women, these fingers are usually the same length or the index digit is just a bit longer.

Digits are subtly affected by testosterone and estrogen produced in the womb by the fetus (not by the mother). Between weeks 8 and 14, tiny fetal testes, ovaries and adrenal glands secrete the baby's own supply of sex hormones. These chemical messengers, particularly testosterone, cause chain reactions in the body, spurring the growth of the genitals, encouraging and inhibiting growth in brain regions and causing changes in the fingers. Many scientists believe relative finger length—or digit ratio—is a marker for brain differences molded by hormones. Like a bit of prenatal graffiti, a longer ring finger says, "Testosterone was here."

John Manning, a biologist at the University of Liverpool, first identified digit length as a sign of prenatal hormones eight years ago. He believes digit ratio is an important, if indirect, tool for studying the fetal brain and the womb, an environment that's off-limits to scientists except for analysis by amniocentesis. (And even then, because sex hormones fluctuate hour by hour, amniocentesis is a poor indicator of testosterone exposure.)

"Early sex hormones have an organizing effect on the brain that's permanent," Manning says. But the differences between the sexes aren't all that interesting to biologists. More telling are the variations within each sex. Females with masculine digit ratios have more masculine behaviors, he says. Likewise, males with a typically female ratio exhibit more typically feminine behaviors.

A recent study of digit ratio in Scottish preschool children between the ages of 2 and 4 found strong relationships between digit ratio and gender-normative behavior. Girls with masculine-type finger ratios tend to have higher hyperactivity scores and more problems relating to their peers than do other girls. The same study, published in Early Human Development, found that boys with female-type finger lengths are on average more emotional than other boys. "They tended to be very sensitive," says Manning.

Except for genitalia, relative finger length is the only physical trait fixed at birth that is sexually dimorphic—meaning males and females show typical gender differences. Other sexually dimorphic traits, such as height and waist-to-hip ratio, don't appear until puberty.

"Everything you see as far as sex differences in the behavior of toddlers is an aftereffect of prenatal testosterone," says Dennis McFadden, a psychology professor at the University of Texas at Austin. Manning and others have linked finger length ratios to aggression, left-handedness, heart disease, autism and attention deficit disorder, all traits that are more common in men. (Studies indicate they are most common in men with longer than average ring fingers.) A "masculine" finger pattern seems to similarly mark girls predisposed to hyperactivity and autism.

Some scientists believe prenatal sex hormones are also part of the puzzle of homosexuality and that a high level of testosterone may wire the brain for attraction to the same sex. Intriguingly, research shows that a prenatal testosterone level is most strongly linked to homosexuality in women, according to a recent article in the Archives of Sexual Behavior. Lesbians are more likely than straight women to have a masculine finger ratio, says McFadden.

The data in men, however, are more complicated and contradictory. Some studies have shown hypermasculine finger length in gay men, while other studies show the opposite, a female-like finger pattern. The picture is further muddied by geography. Race and ethnic differences seem to affect digit ratio, although scientists don't yet understand how.

Still, even if prenatal testosterone is a factor in homosexuality, it's unlikely to be the only element. Studies indicate genes wield much influence.

Even as digit ratio research flourishes and more behavioral links are established, the relationships will remain mere statistical correlations until researchers fully understand how sex hormones physically affect the brain. The reigning hypothesis is that testosterone encourages growth in the right side of the brain, while inhibiting growth in the left. Animal models using rats, mice and sheep show that testosterone boosts growth in a part of the hypothalamus involved in sexual behavior and fertility. In sheep, males with hypermasculinized brains are sexually attracted to other males.

You may be tempted to draw conclusions from your own fingers. But it's impossible to do so accurately in a vacuum, cautions Manning. Fingers are an indication of the environment that molded the brain, but only if you know how you measure up to others.

"You have to be careful," he says. "You can't look at someone's fingers and make a determination about whether they are heterosexual or lesbian, just as you can't decide whether they're neurotic. The [sexuality indicators] are most certainly there, but they're not strong enough to allow us to make predictions."

http://www.amren.com/mtnews/archives/2005/03/fingers_point_t.php
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Canadian researchers say they’ve found a way to help ‘finger’ men with physically aggressive personalities.

A University of Alberta study finds that measuring a man’s index finger length relative to his ring finger length predicts his predisposition to being physically aggressive.

The shorter the index finger relative to the ring finger, the higher the amount of prenatal testosterone and the more likely the man will be physically aggressive, they researchers say.

In a prepared statement, study co-author Dr. Peter Hurd admitted he initially thought the finger-aggression link was “a pile of hooey,” until he reviewed the data.

According to the researchers, experts have known for a hundred years that the index-to-ring finger length ratio of men differs considerably from that seen in women. And more recently, research has suggested that the length of men’s fingers changes depending on their exposure to testosterone in the womb.

http://www.quazen.com/Science/Biology/Length-of-fingers-determine-sporting-ability-and-sexuality.5333
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A number of studies have been carried to investigate how people's individual characteristics correlate with their finger lengths. This article brings together some of the findings.

In recent years a number of studies have been carried to investigate how people's individual characteristics correlate with their finger lengths. These studies have been based on comparisons between the length of the individual's index finger and the length of their ring finger.

These studies have revealed correlations between finger lengths and individual characteristics such as testosterone levels, risk of heart attack, sporting ability, sexuality and even penile size.

In the majority of women, the index and ring fingers are almost equal in length. While in men, the ring finger is usually noticeably longer than the index finger.

In the largest study of its kind, carried out at Kings College London, it was shown that women with a longer ring finger were more likely to be good at sports such as tennis, swimming and skiing. However, the same study also showed a correlation between women with a longer index finger and an increased prowess in cricket, martial arts and gymnastics.

Male sporting ability can also be linked with finger length as revealed in a study carried out by John Manning of the University of Central Lancashire. John Manning’s findings revealed that men with longer index fingers are more likely to be better sportsmen.

Another discovery based on a study carried out solely on females was by a group of scientists from the University of California at Berkeley. This controversial study showed that lesbians showed a greater propensity to have a significant difference between their index finger and ring finger than was shown in heterosexual women.

It came to light in a study by the University of Alberta that men with short index fingers tended to be more aggressive which is linked to higher testosterone levels and a greater chance of heart attack in early adulthood.

A Greek scientist from the Naval and Veterans Hospital of Athens has discovered that the length of the index finger can accurately predict the length of the penis. It is claimed that these findings will help doctors counsel and treat men who suffer from perceived inadequacies in this area.

The University of Alberta study on males showed that finger length is dictated by womb environment. Men with several older brothers were shown to be more likely to have significantly shorter index fingers. This is thought to be due to the increased amount of androgen in the mother's womb. However, Professor Spector's study at Kings College, London, which was carried out on females, showed that finger length is 70% heritable and womb environment was revealed to have little influence on the length of the female fingers. Despite this, scientists are yet to discover a gene which dictates finger length.
 

Offline that mad man

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finger length
« Reply #2 on: 20/04/2007 15:28:54 »
I think they are different lengths so that we can grip well.

Put your hand out straight looking at the palm and notice the different lengths. Now slowly cup your hand into a grip, the fingers will fit the curve of the palm.

Bee



 

another_someone

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finger length
« Reply #3 on: 20/04/2007 16:22:53 »
I think they are different lengths so that we can grip well.

Put your hand out straight looking at the palm and notice the different lengths. Now slowly cup your hand into a grip, the fingers will fit the curve of the palm.

Bee

Given that each finger can be moved independently, when you curl up your fingers, you can achieve almost any configuration you wish, no matter what the actual lengths of the fingers are.

If there is a functional benefit to be gained by having fingers of different lengths, it is probably more to do with the fingers being better at performing different tasks, just as the thumb (which is just a modified finger) also performs a different function.

On the other hand, it is just as possible that there is no actual benefit to the different finger lengths, and it is merely a byproduct of the way the fingers were produced (i.e. when you look at the components in any machine, you often find that components are not necessarily designed to be functionally optimal, but are often designed for ease of manufacture).
 

lyner

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finger length
« Reply #4 on: 20/04/2007 23:15:19 »
I thought the long middle finger was there to enable us to signal  our displeasure, effectively to other drivers.
 

Offline Carolyn

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finger length
« Reply #5 on: 22/04/2007 03:35:05 »
I thought the long middle finger was there to enable us to signal  our displeasure, effectively to other drivers.

LOL...that's what I thought too! ;D
 

The Naked Scientists Forum

finger length
« Reply #5 on: 22/04/2007 03:35:05 »

 

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