When researcher Tristan Darland put cocaine on a pad and stuck it on one side of a fish tank, fish liked the feeling they got so much that they hung around the area, even after the cocaine was removed.
Then Darland bred a family of fish that had one gene altered. These fish resisted the lure of the cocaine.
Darland says this shows that addiction is largely genetic. "These fish don't know anything about peer pressure. They either respond or they don't respond to the drug," he says.
At the Medical College of Wisconsin, Dr. Robert Risinger scans the brains of human addicts while they watch a video of people getting high on crack. It's what they call a "craving" video. He then shows them a hard-core sex film.
The brain scans show the addicts get more excited by the craving videos. The drugs become more powerful than sex — because addiction's a disease that changes your brain, says Dewey.
I asked Dewey if he was suggesting that drug users don't have free will.
"That's correct," he said. "They actually lose their free will. It becomes so overwhelming."
But if they don't have free will, how come so many people successfully quit?
Is the Disease Message Harmful?
Addiction expert Sally Satel acknowledges drug addiction and withdrawal is "certainly a very intense biological process." But she is one of many experts who say the addiction-as-brain-disease theory is harmful to addicts — and wrong.
She also thinks it's unhelpful to take away the stigma associated with drug abuse. "Why would you want to take the stigma away?" she asks. "I can't think of anything more worthwhile to stigmatize."
"People need to get rid of the idea that addiction is caused by anything other than themselves," says James Frey, author of A Million Little Pieces, a book about his experience as an addict.
Frey says he took just about every drug, from alcohol to crack. Yet Frey says he wasn't powerless. He scoffs at Dewey's claim that addicts' brains compel them to keep taking drugs.
Many doctors agree, saying you can still choose not to take drugs, even if they do cause changes in your brain.
"You can look at brains all day," Satel says. "They can be lit up like Christmas trees. But unless a person behaves in a certain way, we wouldn't call them an addict."
Environment and Choice
In fact, some researchers cite experiments that they say prove that addiction is a matter of choice.
In Canada, researchers gave rats held in two different environments a choice between morphine and water. The rats in cages chose morphine; the rats held in a nicer environment preferred the water.
Whether you get addicted also depends on how you're treated. At Wake Forest University, male monkeys lived together for three months, and established a pecking order.
The monkeys who'd been bullied by the "boss monkeys" banged a lever to get as much cocaine as they could. But the dominant monkeys, just by virtue of being dominant, had less interest in the drug.
"It's just like the human world," says Dr. Michael Nader, who conducted the experiment.
"Individuals that have no control in their job show a greater propensity for substance abuse than those that have control," Nader says.
These comparisons suggest that addiction is a choice — not a disease that takes away free will.
The message from the treatment industry is that drug users need professional help to quit. What they seldom say is that people are quitting bad habits all the time without professional help.