People who can write with both their right and left hands are more likely to be bisexual, new research has found.
For years, scientists have been fascinated by left-handed people, and a number of studies have suggested that southpaws are more likely to be homosexual, or to suffer from certain illnesses and disorders.
Not true, according to University of Guelph psychology professor Michael Peters. He and his colleagues found no differences in the health or sexual preferences of right-handed and left-handed people.
"In fact, they were remarkably similar to each other in all of the comparisons we looked at," he said.
But those who were ambidextrous, at least when it came to writing, stood out.
Not only were they more likely to be bisexual, and to a lesser extent homosexual, they also reported suffering from asthma, hyperactivity and dyslexia more than individuals who were more definitive about which hand they prefer.
The study involved 255,000 people who answered questions on the BBC Science and Nature website. Participants were asked 150 questions about demographics, personality, sexuality, social attitudes and behaviours.
The study was not billed as being about left-handedness. That means it didn't attract a disproportionate number of left-handed people, who make up roughly 10 per cent of the population in North America and Europe.
It also did not ask people whether they were left- or right-handed, since people who use both tend to say they are lefties, Dr. Peters said. Instead, volunteers were asked to rate their preference for writing on a scale of one to five.
One meant they liked using their left hand and five meant they preferred their right.
Those who chose three -- about 1 per cent of the participants -- were comfortable with either hand. And they turned out to be the most interesting, Dr. Peters said.
For example, among men, only 4 per cent of right-handers and 4.5 per cent of left-handers reported that they were bisexual.
But among those who wrote with both hands that number was 9.2 per cent.
Among women, 6.2 per cent of right-handers and 6.3 per cent of left-handers reported they were bisexual, compared to 15.6 per cent among the more ambidextrous volunteers.
Dr. Peters and his colleagues, British researchers Stian Reimers and John Manning, published their findings in a recent edition of the journal Brain and Cognition.
They had no way to verify that participants were telling the truth. But they found the percentage of people who said they were left-handed, homosexual, or dyslexic mirrored the numbers found in other large studies.
Their research is the latest offering in a field full of contradictory findings.
For example, in 2000, researchers at the University of Toronto and the Centre for Addiction and Mental Health found that being left-handed is more common among lesbians, and to a lesser extent among gay men.
Others have investigated whether being left-handed is associated with dyslexia, hyperactivity or asthma.
The ambidextrous have received much less scientific scrutiny.
Dr. Peters is ambivalent about the term, because it implies people can write equally well with both hands.
This is rare, he says, and usually people are more skilled with one hand than the other, even if they can use both.
He says it is hard to know whether baseball players who can hit both ways, such as Pete Rose or Mickey Mantle, are truly ambidextrous, or whether they have worked hard to acquire a difficult skill.
Same with soccer players who are adept at kicking the ball with both their feet, such as German Gerd Mueller.
Russian tennis player Maria Sharapova is so good with both hands that she played left-handed as a junior.
"At one point, I didn't know if I was going to play lefty or righty or both hands," she has said.
All young children experiment with both hands.
"There is a phase, that can be longer or shorter, in which the parents say, 'Oh, he's going to be left-handed,' or 'Oh, he's going to be right-handed,' " Dr. Peters said.
"In the end, it shakes down by three, four or five years and focuses on one or the other."
Left-handed kids can take longer to declare themselves, he says, but children who don't make a choice are likely to use both hands as an adult.