My response to Princess's post on Desire & Arousal:
Most research I have read seems to find that women have a spit between subjective (mental) arousal and physiological arousal. Women can show all the physiological measures of arousal and say that they don't feel turned on at all.
One reason I think might play into this is the issue of distraction. From what I have read women have far more problems with maintaining focus during sex. A lot of it is connected with body image. Some women get so distracted by how they look that they can't focus on their feelings.
Also, in order to get aroused a woman must go within and focus on her own sensations. Unfortunately, the female gender role is all about pleasing others. It's hard to focus on your own needs when you feel you are supposed to be pleasing a partner.