Australian scientists have found out what part of the brain is responsible for sexual attraction between people. They also found out that the bigger that part of the brain is, the faster and more intense man's excitement is.
Amygdala
The researchers, a group of neurophysiologists from the University of Melbourne, say that the degree of excitement depends upon the activity of the part of the brain called 'amygdala'. This part of the brain has the size of an almond. When you feel sexual irritants, the amygdala will respond faster than any other part of the brain.

Before the researchers discoverd this, it was already believed that the amygdala was responsible for attraction between animals.

After examining 45 epilictics of whom part of the brain is not working, amygdala included, it turned out that the amygdala plays a large role in the sexual experience. The bigger the amygdala, the bigger the sexual lust. People with large parts of the amygdala not functioning were almost indifferent to sex.