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. NY: Arbor House Publishing, 1983, pp 243-253)