Some women are woken in the night by the intense pleasure of an orgasm. There’s usually no ejaculate, but the vagina does become wet and lubricated.
Yet women’s night-time climaxes largely remain a mystery, says Dr Laan, who specialises in studying the differences between male and female sexual arousal.
“Why don’t we know more about women’s experiences? Because women’s organs are on the inside. They can’t see and feel what’s happening to their genitals the way men can.”
For men, you know you’ve had a wet dream, or ‘nocturnal emission’, when you wake up and feel the damp patch on your bed. You might think you’ve peed, but in fact, it’s semen. It happens spontaneously and often men have a wet dream without even dreaming about sex.
“Men have about four to five erections a night, connected with rapid eye movement,” Dr Laan says. “We think this happens because it’s good for sex organs to be engorged with blood on a regular basis – it’s healthy for the tissue.”
Friction or squeezing
The same also applies to women. “We have studies measuring vaginal reactions during sleep and you see the same pattern of arousal that you see in men.”
While women’s genitals become engorged, it usually takes a little more stimulus to produce an orgasm.
“So suppose you’re a woman in this cycle. If your sensitivity threshold is low, you may only need a little bit of friction or a little bit of squeezing of the muscles in the groin to give you an orgasm. This is often instinctive because you’re half asleep.”
To protect the identity, the person in the picture is a model.