The brain of a gay man is clearly different from a straight man's; no wonder that even their bodies function differently. A new Canadian research published in the journal Neuropsychology and made on gay men comes with new aspects on the link between sexual orientation and right or left-handedness.

Homosexuals of both genders had been known to have a 39 % increased probability to be left-handed compared to heterosexuals. But the new research also shows higher rates of extreme right-handedness. The new research also strengthens other findings showing that having older brothers increases the chances for men to be gay. It seems that the number of older brothers controls the connection between handedness and sexual orientation: the extreme right-handedness is encountered only in men missing or having few older brothers.

"These new research findings add further weight to the idea that biological factors play a significant role in the development of sexual orientation," said Robert-Jay Green, Executive Director of the Rockway Institute, a national center for lesbian, gay, bisexual, and transgender research and public policy at Alliant International University.

The research was made on 538 gay or bisexual men and 373 heterosexual men interviewed about their handedness for 10 physical activities, but also about the number of biological brothers. Most subjects were right-handed, but gay/bisexual men displayed an increased chance of both left-handedness and extreme right-handedness compared to the straight subjects. "The number of older brothers increased the likelihood of being gay or bisexual in moderate right-handers only. In both non-right-handers and in extreme right-handers, older brothers either did not increase or lowered the likelihood of being gay or bisexual.", wrote author Anthony F. Bogaert of Brock University in St. Catharines, Ontario.

"If elevated extreme right-handedness is an indication of early neurodevelopmental anomalies, then an elevation of this handedness pattern in gay or bisexual men gives additional evidence that one route to same-sex attraction is through early developmental stressors (in the womb) or through a factor correlated with such stressors. Still, a genetic explanation can also be forwarded.", he added, as researches have found genes involved in both handedness and sexual orientation.

There are genes involved in handedness which also control the immune system and immune reactions are believed to influence male births. "In conclusion, the main findings-evidence of extreme right-handedness in gay men, along with the moderating effect of older brothers at both ends of the handedness continuum-potentially move forward two important research programs (on handedness and birth order) related to men's sexual-orientation development.", wrote Bogaert.

"The results of this research suggest there is a biological predisposition to homosexuality among a significant number of gay/bisexual men. What we don't know yet is how strong or widespread such biological predisposition is or whether it is a result of genes, maternal hormones during pregnancy, or maternal immune system functioning during conception.", said Green.