The Urge to Gamble May Be All in Your Head
It appears to cause changes in brain chemistry
By Jennifer Thomas
A new study suggests gambling may cause changes in brain chemistry that encourage continued gambling, even when you're losing.
The researchers behind the study believe that when gamblers place bets and eagerly await the results, the act of taking a risk may cause a surge in the release of the neurotransmitter dopamine in the brain.
While the precise role of dopamine is not fully understood, addictive drugs such as cocaine and nicotine are known to increase dopamine levels in the brain. And diseases such as Parkinson's result in the death of dopamine-producing cells, says study author Christopher Fiorillo, a post-doctoral fellow at Cambridge University in England.
The study appears in the current issue of Science.
Fiorillo and his colleagues outfitted monkeys with electrodes to measure the activity of neurons in the brain that produce dopamine. Then they put the monkeys through a simple test. Again and again, the monkeys were shown one of five objects on a TV screen. Each object corresponded with some probability of getting a reward, in this case a drop of juice.
The probability of getting the juice ranged from no chance to a 100 percent chance. In mathematical terms, the probability of getting the juice ranged from zero to 1.
The researchers found that when the monkeys were least certain about getting the juice, the neurons in the dopamine-producing portion of their brain were the most active.
"What was so interesting and strikingly novel about this pattern of firing was that it seemed to track the uncertainty," says Peter Shizgall, a professor of psychology and director of the Center for Studies in Behavioral Neurobiology at Concordia University in Montreal. He wrote an accompanying commentary in the journal.
The concept of uncertainty is frequently misunderstood by non-scientists. For instance, many people would mistakenly believe a monkey's uncertainty would be highest when there was no chance of getting the juice, the researchers say.
In probability, uncertainty is highest when the chance of something happening is 0.5. Or, in the case of the study, when the monkeys were shown an object that carried a 50 percent chance of leading to juice.
Uncertainty was low when the monkeys were sure the juice was coming or not coming. When the monkeys were shown those corresponding pictures, the researchers didn't observe the spike in neural activity.
The researchers also observed that when uncertainty was high, increasing the level of reward (in this case, increasing the amount of juice dispensed) caused a rise in the level of neuronal activity.
While Fiorillo's research was on monkeys, he and other researchers believe the experiments might give some insights into human behavior, specifically, why people would gamble even when the odds are they will lose.
"There is a large amount of work that's already been done that shows dopamine acts in the brain to reinforce behaviors," Fiorillo says. "If a behavior is followed by an increase in dopamine, it's more likely to be repeated."
Cocaine, for example, increases levels of dopamine, which is known to be a catalyst that promotes continued use of the drug. Experiments have shown other activities, such as falling in love or exercise, can also boost dopamine levels.
"This present work suggests that uncertainty about reward may itself have a similar effect, and uncertainty about reward is the defining feature of gambling," says Fiorillo, who conducted the research while at the University of Fribourg in Switzerland.
Why would a system in the brain encourage risk-taking?
"One possibility is that risk-taking promotes exploration and learning in natural environments," he says. "Obviously, this system is not useful in a casino, where no amount of experience will allow a person to significantly improve his or her odds of winning."
Shizgall says the new study adds to growing interest and research about the interplay of emotions and reasoning in decision-making.
Say, for example, you're playing roulette and you place your chips on red. There's a 50 percent chance you'll win.
But say you've been watching the game for awhile and red has won the last 10 times. "Your gut is going tell you black is due," Shizgall says.
In fact, statistically, the probability of red coming up again hasn't changed -- it's still 50 percent with each spin of the wheel.
"Even if you know this, the excitement of the casino and the anticipation of a reward will play a role in how you place your bet or if you place your bet," he says. "Emotion and cognition both play a role."
For help with compulsive gambling or a gambling addiction, visit the National Council on Problem Gambling or Gamblers Anonymous.
SOURCES: Christopher Fiorillo, Ph.D., post-doctoral fellow, Cambridge University, England; Peter Shizgall, Ph.D., professor, psychology, and director, Center for Studies in Behavioral Neurobiology, Concordia University, Montreal; March 21, 2003, Science
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