Brain imaging: Gay males and women responded to two odors (thought to be involved in sexual arousal) in the same way. Heterosexual males responded differently. (Dowd, Maureen. Are Men Necessary? p 152-156. NY: G. P. Putnam’s Sons, 2005.)

The female brain is less arousable than the male brain and responds differently to visual/auditory arousal stimuli. Study: levels were higher in males than females after viewing an erotic film. Influenced by testosterone, norephinephrine tends to rise with hyperactivity, euphoria, self-assertion, and aggressiveness. (Durden-Smith, Jo, and Diane deSimone. Sex and the Brain. p 243-254. NY: Arbor House Publishing, 1983.)