Scientists say a man or woman's sex drive may be proportional to the size of a part of his or her brain.

Australian researchers from the University of Melbourne believe the size of the amygdala,
a miniature "emotion" centre that is nestled at the base of the brain may determine how
much sex a person wants, reports Nature News Service.

As small as an almond, the amygdala has long been known to process our reactions to fear.

Previous studies have shown, for example, that the amygdala is stimulated by erotic movies,
and it's considered vital for mating behaviour in many animals.

The Australian team, led by David Reutens, scanned the brains of 45 patients who had chronic
epilepsy, which is known to short-circuit sex drive.

Nature News notes that as part of the treatment for epilepsy, each had undergone surgery to
remove part of his or her brain, which freed up the remaining areas to run more normally.

Those patients who had the greatest amount of amygdala left intact after the surgery also
had the greatest sex drives. Reutens suggests this means the amygdala boosts the likelihood
of a sexual trigger that leads to arousal, reports Netscape.

"They discovered something quite extraordinary," Jim Pfaus, who studies sexual behaviour at
Concordia University in Montreal, Canada, told Nature News.