The structures they studied are all components of the brain's reward circuitry: ventral striatum, insula and vmPFC (pre-frontal cortex).

So, where's the problem? The problem is that our genes have hidden agendas. Food and resources register as rewarding because they promote survival, but the most powerful rewards are for behaviors favoring more progeny, whatever the risks. Think of Karen Owen's screw-'em-and-rate-'em behavior, or the escapades of Bill Clinton, Mark Sanford and John Edwards, Larry Craig's bathroom antics and George Reker's "rent boy" caper. Consider the fact that HIV cases in gay men under thirty have jumped more than thirty percent since 2001.

These folks have one thing in common: Their inner compasses aren't functioning in accord with their long-term self-image, because a primitive brain mechanism assesses their risky activities as—believe it or not—genetic opportunities. "Selfish genes" indeed!

How do our genetic programs pull our strings? In this case, by releasing extra dopamine (the "gotta get it" neurochemical) in our reward circuitry. We don't realize what's going on because we're used to relying on input from this circuitry as we make countless other, generally sound, decisions. So, when hit with extra dopamine, we just know we need to act on that impulse, and actively resist unwanted, more sober thoughts. Sneaky, eh? On the other hand, when dopamine (sensitivity) plummets, we may feel bored, or like we don't want more of something (or someone)—or like we just made a huge mistake the night before.

Whether unusually high or low, we're on a mini-drug trip or having a bit of a hangover. Either way, we're laboring against chemically induced odds. Fortunately, the impulses pass—before or after we act—and clarity generally returns.

When moral-compass malfunction lingers

Some of us arrive on the planet with brains that make us more impulsive or prone to overvaluing novelty, thus skewing our compasses. However, it's likely that most of us are susceptible to lingering compass malfunction (that is, distortion  of limbic tone) in one circumstance: Engage in too much intense stimulation and another genetic program kicks in for a time: the binge program. 

Let's say you discover a racy online chat room or a titty bar. Surrounded by all those potential mates, your brain releases extra dopamine ("Yes!"), coloring your perceptions and often your judgment for a time. In fact, today's opportunities to be turned-on by novel, hot potential mates, synthetic sexual stimuli and hyper-stimulating junk food register as so valuable to many brains that they automatically suppress their sensitivity to keep their owners seeking more goodies. Instead of feeling greater satisfaction, such folks often experience growing malaise (unless and until their brains reboot).

These subtle, but very real, brain changes occur without conscious awareness. To restore equilibrium and sound judgment, they need time without intense stimulation, (but, preferably, lots of affection or friendly interaction). Until they're back to normal, even a beloved may look...unsatisfying. Said one man after lots of hot sex for two weeks in a new relationship,

I feel dumb for getting involved with a woman who wants a steady relationship. She is good woman. I like her, but when I interact with other women and the chemistry is there, it's hard to ignore.

His reward circuitry is overvaluing the promise of intense stimulation (via novelty) because dopamine is surging in his numbed brain at the very thought. He feels a restless need to act.

Here's the thing: Neither his cravings nor their consequences have much to do with his moral character. The culprit here is limbic tone. It can produce a fog of unsettling perception distortions, inner conflict, and self-doubts. We act without realizing we're under a spell. When our neurochemistry shifts again, we wonder, "What was I thinking???" Answer: we weren't; we were on neurochemical autopilot, or at least suffering from distorted perception that enabled us to rationalize reckless behavior.

Consider this exchange about how extreme sexual stimulation shifts perception even among solo porn users. (The issue here isn't porn. It's the shift in perception, which can happen after too much stimulation of any kind.)

First person: Porn takes you outside the norm of what you think sex should be. It takes you to "everything goes" land where it's okay to abuse and hurt others and it doesn't matter if love exists in the couple. In fact, the less love, the more depravity, the better! When you're fully addicted you can see nearly ANYTHING happen on screen. Hell, I was happily watching urination, vomit, people hitting and abusing each other, people with disabilities being humiliated and mistreated, even people having trash dumped on them—all without even thinking about it. It was disgusting but I didn't care. When my mind was in that "space," anything went.

So after months of no porn, I clicked on some of the stuff I knew I had always liked, and just got this horrid feeling of, "WHAT THE HELL AM I WATCHING?" I was back to normal and I was seeing it as myself, with my rational and sane eyes...and it was completely disgusting. Porn wasn't about what kind of sex I liked, it was about seeing intense, violent and exciting stuff when I was in that space.

Second person: Time passes, and the feelings of "No, not again!" become, "This is just who I am, I guess." It would be good to alert new porn users to what may turn them on down the road. But only when they see how they change will they truly understand how morphed they become without realizing it. Getting off to someone getting vomit in their eyes and crying in pain as a scene keeps rolling can hit people's minds harder than a strong mushroom trip. Naive people only realize life is not porn once they try the stuff they see. Hopefully as people hit their own walls, they will too take a step back and ask, "What have I become?"