Everyone is convinced of his/her point of view—and can usually point to surveys to 'prove' it. Yet what if the porn debate could be moved to another playing field and resolved using hard science?

Good news. Non-invasive tools now exist for peering into the brains of Internet porn users. The techniques have already been used extensively to examine the brains of pathological gamblers, overeaters and drug users.

If use of Internet porn is indeed harmless, such research will settle the matter definitively. On the other hand, if Internet porn causes addiction-related brain changes in otherwise healthy users, such information is equally vital. Users could learn which symptoms are problematic and make informed choices. Society could better shield and educate youngsters. So,

1. What exactly what would brain researchers be looking for in porn users' brains?
2. Why hasn't this research been done already?
3. And why do diagnostic labels matter anyway?

What could we learn from brain research?

Researchers spent the last eight years running dozens of objective tests on the brains of pathological gamblers. They discovered that excessive gambling causes the same brain changes as substance addictions. Accordingly, psychiatrists are re-categorizing pathological gambling from 'disorder' to 'addiction' in the upcoming Diagnostic and Statistical Manual of Mental Disorders, DSM-5.

The diagnosis of gambling as an addiction confuses those who associate addiction with heroin needles or crack pipes. However, chemical and behavioral addictions are very similar physiologically. After all, chemicals don't create novel processes in the body; they merely increase or decrease existing processes.

Although cocaine, nicotine and gambling feel quite different to a user, they share the same brain pathway and mechanisms. For example, all increase dopamine in the hub of the reward circuit, the nucleus accumbens. To be sure, substance addictions often have toxic effects that natural rewards do not. And some, such as cocaine and meth, cause the sudden release of more dopamine than rewarding behaviors such as gambling. But whether you drive or jog, all these roads can lead to Rome.

Some people also confound "addiction" with "passion," such as a passion for golf or sex. They imagine that any activity a person finds compelling is "addictive," rendering the term so meaningless that no activities can be considered addictive. In fact, 'addiction' is no longer an amorphous concept, at the mercy of such reasoning. Already, three defining characteristics of addiction can be measured objectively in the brain. Moreover, cognitive tests, and even blood tests, have been developed to check for the presence of such physical changes, without the bother of brain scans.

Here are simplified descriptions of these three key, measurable addiction characteristics:

Numbed pleasure response: Among other changes, dopamine (D2) receptors drop in the brain's reward circuitry, leaving the addict less sensitive to pleasure, and "hungry" for dopamine-raising activities/substances of all kinds. The addict then tends to neglect interests, stimuli, and behaviors that were once of high personal relevance.

Sensitization: Dopamine (the "gotta get it!" neurochemical) surges in response to cues related to the addiction, making the addiction far more compelling than other activities in the addict's life. Also, ΔFosB, a protein that rises with sexual activity and helps preserve intense memories, accumulates in key brain regions.

Hypofrontality: Frontal-lobe gray matter and functioning decrease, reducing both impulse control and the ability to foresee consequences.

No matter how passionate non-addicts are about an activity, these "hard-wired" changes don't occur. Non-addicts can stop at will. Addiction, in contrast, is uncontrolled, compulsive behavior arising from a brain that is neither functioning nor registering satisfaction normally (and therefore suffers symptoms, such as cravings and withdrawal discomfort).

Each of the three phenomena has repeatedly shown up in the brains of pathological gamblers. More recently, scientists have begun to examine the brains of fervent video gamers. They have discovered evidence of substance-addiction-like brain changes and sensitivity to cues, again indicating addiction processes at work. Similar phenomena have been seen in overeaters. 

Why are we studying gambling and not porn?

As yet, we know of no studies on the brains of porn users using today's non-invasive, relatively inexpensive imaging tools. One reason that scientists are not checking Internet porn users for dysregulated brains is that Internet porn is so new. Static porn has been around for a long while, but high-speed Internet has been widely available for the blink of an eye in academic terms. Research always lags behind reality.