A research team from the University of Groningen Medical Centre in the Netherlands has found that watching porn can actually turn off the part of the brain that processes visual stimuli.
The study looked at twelve healthy, heterosexual premenopausal women who took hormonal birth control pills. The women were shown three different films: the first was a control
about marine life in the Caribbean, the second two were so-called
"female friendly" porn. Their brains were then scanned using positron electro tomography (PET scans).
Scans showed that the primary visual cortex received less blood flow when the women were viewing porn. The same
thing also happens when a human conducts a non-visual task like memorizing a
list while being shown some sort of visual "distractor" stimuli. These results could indicate the when it comes to porn, the female brain is more focussed on sexual arousal rather than the actual visual processing of the film.