Why some people are gay？

There is a debate on Same-Sex marriage about weather it will affects kids health.Maybe you are also curious about the psychological and brain activity of homosexual.A research led by Gwang-Won Kim may satisfy your curiosity:

This study was performed to clarify the sexual orien-tation in a 19-year-old homosexual male and a 20-year-old homosexual female by using a functional magnetic resonance imaging (fMRI) with viewing male and female erotic nude pictures. The sex hor-mone levels of the homosexual male and female were in the normal range of healthy heterosexual males and females, respectively. In both homosexuals more significant brain activities were observed while view-ing the nude pictures of the same genetic sex than those of the opposite sex in the frontal cortex, parietal cortex, occipital cortex, anterior cingulate gyrus, amygdala, midbrain, hippocampus, orbitofrontal cortex, parahippocampal gyrus, thalamus, globus pallidus, and putamen, which are known to be re-sponsive to sexual arousal. The homosexual male and female showed a tendency toward higher sexual arousal to the same genetic sex as comparison with the opposite sex.

(source:SCIRP)