Eliezer Yudkowsky posted this most excellent article in the blog Overcoming Bias more than one year ago, but at time I failed to make the connection with porn because I was unaware (or maybe simply refused to be aware).
The premise of the article is that while we humans basically remained the same biologically for the last couple thousands of years, our environment did not and we have a hard time to cope with all the stimuli around us (cleverly labeled as superstimuli) without becoming neurotics or addicts or something in between. I'll paste the most relevant parts here with a comment.
A candy bar is a superstimulus: it contains more concentrated sugar, salt, and fat than anything that exists in the ancestral environment. A candy bar matches taste buds that evolved in a hunter-gatherer environment, but it matches those taste buds much more strongly than anything that actually existed in the hunter-gatherer environment.
Indeed. That's what porn does: it's a candy bar for our sexuality. We men are hardwired to like women; but porn isn't nothing like what our brain is designed to handle.
I feel bad for myself as a man but, frankly, I feel much more pitiful toward women. They are probably even more affected b that than us. We men have an easier time, generally. Not that we don't have our own stock of insecurities - height, penis size, money - but we can even get away with being relatively unattractive, if we can show confidence, sense of humor, security, social status. Things that can be worked out, more or less. I've seen even dwarfs and midgets with georgeous women.
Women have a much harder time. From them, we just expect an illusion. We men grow up accustomed to the ideal of beauty promoted by lingerie models, tv shows, movies, and we expect in bed what we saw in porn movies. And our "ideal woman" must reflect all of that, or else we simply move on and find someone who is eager to comply. We get cognitively addicted to that stuff, to the point that we even ignore women who don't match that ideal and dump the ones who don't measure up to it.
The now-famous Dove Evolution video shows the painstaking construction of another superstimulus: an ordinary woman transformed by makeup, careful photography, and finally extensive Photoshopping, into a billboard model - a beauty impossible, unmatchable by human women in the unretouched real world. Actual women are killing themselves (e.g. supermodels using cocaine to keep their weight down) to keep up with competitors that literally don't exist.
That's the key point: Today we all ten measure up with something that doesn't exist. We men have to measure up with hollywood actors and porn actors. Women even have to measure against Photoshopped stuff.
On the subject of addiction:
Resisting any temptation takes conscious expenditure of an exhaustible supply of mental energy. It is not in fact true that we can "just say no" - not just say no, without cost to ourselves. Even humans who won the birth lottery for willpower or foresightfulness still pay a price to resist temptation. The price is just more easily paid.
Our limited willpower evolved to deal with ancestral temptations; it may not operate well against enticements beyond anything known to hunter-gatherers. Even where we successfully resist a superstimulus, it seems plausible that the effort required would deplete willpower much faster than resisting ancestral temptations.
I even remember an article I read somewhere (must begin to keep track of the stuff) which speculated that we humans have a set number of "Willpower Tokens" we can use in a day. As soon as we run out, we fall back into addiction or have to seek external help to avoid that.
As far as my experience goes, that's true. But I also think that willpower is something that can be trained or even un-trained: I had a lot of willpower when I was younger, but I lost most of it growing up.