Scientists Used Gambling Monkeys To Try To Figure Out Addiction

By Paul Gaita 09/27/18

The experiment's goal was to understand which regions of the brain wield influence over decision-making.

monkeys playing poker

The behavior of a pair of monkeys with a taste for juice—and gambling—may suggest that risky decisions, from high stakes betting to criminal behavior, is less of a personality trait and more an issue of brain circuitry.

Scientists conducted an experiment in which the monkeys were taught to play a computer game that rewarded them with juice, the amount of which varied depending on the risk level of their decision.

When the scientists found that a region of the brain involved with eye movements became activated when the monkeys took greater risks, they temporarily deactivated the region—and found that the test subjects made far less rash decisions.

The research suggests that risk preference is not fixed but adaptable, and by understanding the brain function involved in those decisions, help could be provided for individuals who have "decision-making disorders" like substance or gambling dependency.

The research, conducted by scientists from Johns Hopkins University and published in the September 2018 edition of Current Biology, sought to determine whether risk-taking was a personality trait—in short, "that some people are risk takers and others are not," said study co-author and Johns Hopkins associate professor Veit Stuphorn. 

The scientists devised a computer game in which the test subjects—two rhesus macaques—were offered two choices: one, which provided a guaranteed but small amount of juice, and the other, which might bring a more substantial amount of juice, or none at all. To indicate their choice, the monkey would move their eyes in each round.

What the scientists found was that the monkeys consistently chose the bigger but less safe option, even in the face of getting consistent but smaller amounts of juice instead of none at all.

They also discovered that the supplementary eye field (SEF)—a region in the frontal lobe of primates' cerebral cortex that is involved in eye movement, and possibly in the eye's role in decision-making—became very active when the monkeys earned a larger reward.

But as NPR noted, the activity didn't prove that it correlated with the monkeys' behavior, so the scientists temporarily deactivated that area of the brain through cooling. Once inactive, the monkeys made safer bets by choosing the smaller but consistent option for juice.

The study findings do not conclusively determine that the SEF is responsible for high-risk decision-making; rather, it suggests that making risky decisions is not a set and permanent aspect of an individual's personality.

The brain might alter those choices based on a number of factors, including the level of reward. It's also possible that other regions of the brain may be complicit in making high-risk choices. 

Understanding which regions of the brain wield influence over decision-making could have far-ranging implications in the treatment of conditions that involve rash choices.

"One would be to help people who have decision-making disorders, whether that's problem gambling or addiction, or other things like that," said Michael Platt, the James S. Riepe University Professor of neuroscience, marketing and psychology at the University of Pennsylvania. "We might be able to develop more effective therapies."

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Paul Gaita lives in Los Angeles. He has contributed to the Los Angeles Times, Variety, LA Weekly, and The Los Angeles Beat, among many other publications and websites.