The sexes are different. Especially when it comes to the experience of sex.

For 20 years, neuropsychologist Dr. Louann Brizendine, author of "The Female Brain," has studied the differences between the sexes. There is a biological reason why men and women are so different in the bedroom.

1. It's All About Timing

• Men take about three to five minutes, on average, to reach orgasm.
  
• Women take up to 13 minutes to reach orgasm.
  "Temperature and comfort are very important to achieving orgasm," Brizendine explained on "The Oprah Winfrey Show." "Researchers in the lab found that if they didn't keep the women's feet warm, they had difficulty reaching climax. So cozy socks may not be sexy, but they get the job done."

• Men just have to think about or visualize sex and blood rushes to the penis.
  
• Women need much more to get in the mood.
  "Foreplay for men is everything that happens about three minutes before sex," Brizendine told Oprah. "Whereas for females, it's everything that happens the 24 hours before sex. Because if she gets upset or angry about something, then she's not in the mood by the time sex is going to happen."

• Two parts of a woman's brain are larger than a man's brain: The memory center, called the hippocampus, which helps people remember the details of emotional events, and the worrywart center, called the anterior cingulate cortex.
  "For example, women may remember all kinds of fights they had with their husband that he may not even remember happened at all," Brizendine told Oprah. In addition, because the worrywart center of the brain is so developed, it's one reason women worry so much more than men.