Watch America's foremost authority on drugs smash a huge misconception about addiction - with chocolate

If drug addiction is a disease like cancer or Alzheimer's, how do you explain the seemingly amoral behavior - the lying, cheating, and hiding - that has come to be linked with so many addicts?

The answer has less to do with morality and much more to do with physical changes in the brains of those who become addicted, as National Institute on Drug Abuse Director Dr. Nora Volkow perfectly explains in a recent PBS episode of "The Open Mind," on addiction.

It makes a lot of sense - especially when explained with chocolate.

Volkow is a chocolate lover, you see. She has a special weakness for dark varieties. Most of the time, she can control her cravings. But occasionally - usually when she's frustrated or tired or bored - she gives in. Then she'll overdo it, and eat too much of the stuff.

Sound familiar?

If so, that's because it's a fairly common type of experience. Most of us can abstain some of the time and give in occasionally, but more often than not, most of us easily follow the rule of moderation. But in people who are vulnerable to addiction (via a mesh of factors including genetics, environment, behavior, and exposure), this is where things start to look different, Volkow explains. And it's at this point where the long-held notion that addiction is merely a problem of a lack of self-control begins to crumble.

"When you transition from that stage where most of the time you are able to self-regulate the desires and control and manage your behavior even though you want to do it, you say it's not a good idea - when you lose that capacity consistently, that's when you start to get into the transition of addiction," she says.

But, as she continues to explain, the problem is not simply a behavioral one. It's also influenced by physical changes that happen in the brain - changes that produce marked differences between the brains of people who are addicted and those who are not.

One of those differences, says Volkow, is a dysfunction in areas of the frontal cortex, a part of the brain which plays a key role in helping us analyze situations and make decisions. "But if these areas of the brain are not functioning properly, which is what repeated drug use [can do] to your brain, it [can erode] the capacity of frontal cortical areas."

When that happens, your ability to say no to that chocolate bar gets diminished, or in Volkow's words, "your ability to make optimal decisions gets dysfunctional."

Volkow's ideas are bolstered by decades of research, including a 2011 review of studies that she co-authored for the journal Nature. The authors of a 2004 paper built upon similar research, concluding that addiction is a learned behavior linked with fundamental changes to the brains of addicts.

For this reason, it's not as simple as just choosing to use drugs - or, in Volkow's example, overdo it on the chocolate. And the more we know about the neurological basis of addiction, the better we will be able to treat it.

Watch the full "Open Mind" episode on PBS: