Doing research for Roll the Bones, I became more convinced than ever that gambling is pretty close to a human universal. I don’t just mean playing slots or picking the Eagles to cover–I’m talking about the more general sense of gambling as risk-taking. Come to find out that it’s not just humans who like to gamble: monkeys are just as happy to bet the house.
From eMaxHealth:
Duke University Medical Center neurobiologists have pinpointed circuitry in the brains of monkeys that assesses the level of risk in a given action. Their findings, gained from experiments in which they gave the monkeys a chance to gamble to receive juice rewards, could give insights into why humans compulsively engage in risky behaviors, including gambling, unsafe sex, drug use and overeating.The researchers, Michael Platt and Allison McCoy, published their findings in the advanced online version of Nature Neuroscience, posted August 14, 2005. The research was sponsored by the National Institutes of Health, the EJLB Foundation, and the Klingenstein Foundation.
In their experiments, the researchers gave two male rhesus macaque monkeys chances to choose to look at either of two target lights on a screen. Looking at the “safe” target light yielded the same fruit juice reward each time. However, looking at the “risky” target light might yield a larger or smaller juice reward. The average juice reward delivered by looking at either target was the same.
To their surprise, the monkeys overwhelmingly preferred to gamble by looking at the risky target. This preference held, regardless of whether the scientists made the risky target reward more variable, or whether the monkeys had received more or less fruit juice during the course of the day.
“There was no rational reason why monkeys might prefer one of these options over the other because, according to the theory of expected value, they’re identical,” said Platt. The researchers also tested whether the monkeys were simply responding to the novelty of the risky target.
In fact, when the researchers made the average payoff for the risky target less than for the safe target, “we found that they still preferred the risky target,” said Platt. “Basically these monkeys really liked to gamble. There was something intrinsically rewarding about choosing a target that offered a variable juice reward, as if the variability in rewards that they experienced was in itself rewarding.”
Even when the researchers subjected the monkeys to a string of “losses,” the high of a “win” appeared to keep them going, said Platt.
“If they got a big reward one time on the risky choice, but then continued to get small rewards, they would keep going back as if they were searching or waiting or hoping to get that big payoff. It seemed very, very similar to the experience of people who are compulsive gamblers. While it’s always dangerous to anthropomorphize, it seemed as if these monkeys got a high out of getting a big reward that obliterated any memory of all the losses that they would experience following that big reward,” said Platt.
Confident that they had developed a valid animal model that would reveal insights into the brain mechanism for assessing risk, the researchers next explored the neural circuitry that governed that assessment. They threaded hair-thin microelectrodes into a brain region called the posterior cingulate cortex, which studies in humans and animals had implicated in the processing of information on rewards. They then measured the electrical activity of neurons in the region as they administered the same behavioral task to the monkeys.
“We found that the neurons behaved very similarly to the monkeys,” said Platt. “That is, as we increased the riskiness of a target, the neurons’ activity would go up in the same way the monkey’s frequency of choosing that target would go up. It was amazing the degree to which the activity of these neurons paralleled the behavior of the monkeys. They looked like they were signaling, in fact, the monkeys’ subjective valuation of that target,” he said. Further analysis of the neuronal activity indicated that, indeed, the neurons were reflecting the risk value the monkeys placed on the target, rather than an after-the-fact response to the payoff.
While Platt and McCoy believed they have isolated one component of the neural machinery of risk, they do not believe they have mapped the entire circuitry.
General Health Articles > Gambling Monkeys Give Insight Into Neural Machinery of Risk
This could be a real blockbuster. Imagine if the “gambling center” of the human brain could be located–the possibilities are endless. By the same token, the thought of monkeys gambling is pretty cool on its own.