As many of you know, the massive experiment of guys giving up porn to heal their ED, social anxiety, porn-induced sexual fetishes, etc. had its roots, in part, on this forum. Last year, Cambridge University addiction neuroscientists, collaborating with a Yale neuroscience addiction expert, finally took a close look at the brains of young men complaining of severe porn-related symptoms.
11 of the 19 reported trouble getting erections/experiencing libido with real partners--but not with porn. This is the first formal acknowledgement of this phenomenon, which has been reported by thousands of men in various forums since the arrival of tube sites with streaming porn.
Subjects also had greater impairments of sexual arousal and erectile difficulties in intimate relationships but not with sexually explicit materials.
Here are some of the hundreds of articles about this research, as well as Gary's notes and a link to the full study itself.
This one was interesting because UCLA's Rory Read gets it completely wrong - claiming the study shows the porn addicts' brains "say...we do like sex more." This directly contradicts the findings of the actual study. In fact the subjects WANT it [the porn vids] more, but they don't LIKE it any more than the controls do. This was one of the main points of the Voon paper. This wanting-more-than-liking behavior is a hallmark of addiction.
According to lead researcher Valerie Voon,
Sexual desire or subjective measures of wanting appeared dissociated from liking, in line with incentive-salience theories of addiction  in which there exists enhanced wanting but not liking of salient rewards.
Compared to healthy volunteers, CSB subjects had greater subjective sexual desire or wanting to explicit cues [BUT] had greater liking scores to erotic cues, thus demonstrating a dissociation between wanting and liking.
Furthermore, this showed up in the subjects' erections. The addicts reported difficulty getting erections to anything but porn. So Reid is wrong that they "liked sex more" than other people. The addicts also had greater impairments of sexual arousal and erectile difficulties in intimate relationships but not with sexually explicit materials highlighting that the enhanced desire scores were specific to the explicit cues and not generalized heightened sexual desire.