Gay men tended to have brains that were more like those of straight women than of straight men -- the right and left sides were about the same size, the researchers found. Gay women's brains tended to be more like those of straight men than of straight women -- the right side tended to be slightly larger than the left.

Next, the researchers used positron emission tomography (PET) scans to examine how a part of the brain involved in processing emotions -- the amygdala -- was connected to other brain regions. Again they found that gay men tended to be more like straight women, with a stronger link between the amygdala and regions involved in emotions. Gay women tended to be more like straight men, with stronger connections to motor functions.