BIRMINGHAM, ALA. — Growing scientific evidence shows that gambling hijacks the brain by triggering a chemical reaction almost like cocaine does, say researchers at the University of Alabama at Birmingham.

The research is showing just how addictive games of chance can be. Further study of pathological gamblers could hit a jackpot of information leading to better treatment for all addictions.

This new understanding of gambling addiction is being led by Don Ross, a UAB professor of philosophy and economics. He is a pioneer in neuroeconomics, a field that looks inside the brain with high-tech imaging to see how people make decisions.

Ross said gambling relies on a key element found in all addiction — a surprise or jolt that triggers a chemical reaction in the brain. Typically, drugs produce this effect, but research shows that gambling does the same thing.

"It's got an action you can do that's guaranteed to get you a surprise," he said. "That's why gambling is addictive — people are surprised if they win and surprised if they lose."

Gambling can produce an incredibly strong drive, really having little to do with money, Ross said.

He cited a case in which three armed men robbed a casino in South Africa. They ordered customers to lie on the floor to be relieved of wallets, winnings and cellphones, he said.

"The pathological gamblers, while lying on the floor, were reaching up and playing slot machines," Ross said. "Now bear in mind, anything they won they weren't going to be able to take home."

These new insights into gambling are included in a recent book of which Ross is lead author. "Midbrain Mutiny: The Picoeconomics and Neuroeconomics of Disordered Gambling" was published earlier this year, and some authorities believe it sets a standard for understanding the underlying neurological mechanism for gambling addiction.

Rudy Vuchinich, a UAB psychologist and book co-author, said neurological studies show that gambling, like other addictions, relies on a reward system that releases a spurt of the brain chemical dopamine.

"If we get rewarded in a surprising way, dopamine is released and that kind of alerts the system how that is going to happen again," he said.

Brain imaging studies show that the neurological footprint of gambling is similar to that left by cocaine.

"Basically, any time anybody takes cocaine it makes this system think it's a surprise reward. It tricks the dopamine system," Vuchinich said. "Gambling does that without drugs."

One of the big questions scientists are trying to answer is who gets addicted to gambling, and why.

Ross said there is mounting evidence that some people are genetically predisposed to addictions. "They become addicted quite quickly," he said.

For the first time, researchers are getting a good idea of what share of people get addicted to gambling, Ross said. Studies last year in the United States, England and New Zealand basically arrived at the same numbers, he said.

"It's starting to look like there's a pretty stable incidence in populations," Ross said. "It's also starting to look like previous studies, especially in America, had really quite considerably exaggerated the prevalence."

The studies show that between 4 percent and 5 percent of people will develop gambling problems from time to time. "They will go through long periods in which they will gamble, but don't have a problem," Ross said.

Then there are hard-core, pathological gamblers that make up 0.5 percent to 0.7 percent of the total population. These are the people who wear diapers to casinos because they gamble so compulsively that they are unable to go to the bathroom, Ross said.

Pathological gamblers found by the American study were highly resistant to treatment, he said.

"They had lower rates of recovery than clinically depressed people, lower rates of recovery than alcoholics, lower rates of recovery than heroin addicts," Ross said. "They were a very small group, but, boy, were they in trouble."

Ross said this group may hold the key to addiction and should be studied. Their addiction can be examined without the complicating factors of drugs and alcohol.

Vuchinich said pathological gamblers could provide insight needed to develop new treatments for gambling and other addictions.

"That very small group holds the key to how this brain reward system can go awry and basically take control of everything the person does," he said. "That's a key part of the addiction syndrome."