In Lab Turned Casino, Gambling Monkeys Help Scientists Find Risk-Taking Brain Area

Understanding why our brains sometimes tell us to do something risky also could help all of us make better decisions, Platt says. The results also could provide nuance to our understanding of free will, said Blanchard, who was drawn to the study of decision making during prior graduate training in philosophy. Alireza Soltani, who was not involved in this particular study but who researches decision-making at Dartmouth College, said the change probably depends on a number of factors, including what is at risk when playing. No gambling was required to get the reward. The monkeys were more likely to choose the guaranteed juice option, Stuphorn says. Researcher Veit Stuphorn, one of the co-authors of the study said that when the area was activated the animals became adverse to taking risks. The researchers suspected a particular area of the brain was responsible for provoking the impulsive decisions; it became very active when making the decision over which option to choose.

Brain cells activated when winning

Adverse to taking risks

The monkeys showed the hot-hand bias consistently over weeks of play and an average of 1, trials per condition. So why do monkeys and humans share this false belief in a run of luck even when faced over and over with evidence that the results are random?

The authors speculate that the distribution of food in the wild, which is not random, may be the culprit. Evolution has also primed our brains to look for patterns, added Hayden. Understanding the hot-hand bias could inform treatment for gambling addiction and provide insights for investors, said Hayden. And investors should keep in mind that humans have an inherited bias to believe that if a stock goes up one day, it will continue to go up. The results also could provide nuance to our understanding of free will, said Blanchard, who was drawn to the study of decision making during prior graduate training in philosophy.

The study was carried out on two monkeys that were taught to play a computer game that gave them drops of juice when they won. According to the researchers, the monkeys enjoy gambling and as such participated voluntarily. There were two potential outcomes for the game — the monkey would either get a guaranteed small amount of juice, or they could gamble to get a lot of juice or no juice at all. The researchers suspected a particular area of the brain was responsible for provoking the impulsive decisions; it became very active when making the decision over which option to choose.

To test their theory, they cooled the part of the brain that had previously been activated when gambling. The monkeys began playing it safe and would not take the gamble as they had previously, instead opting for the surefire option.

Alireza Soltani, who was not involved in this particular study but who researches decision-making at Dartmouth College, said the change probably depends on a number of factors, including what is at risk when playing. These rhesus monkeys play for juice. So Stuphorn's lab had the monkeys play a gambling game while monitoring the activity in their brains. The game had two options. Option one offered a juice reward that was guaranteed but usually small.

Option two was a gamble. Stuphorn says it might bring a lot of juice or none. And the monkey had to choose every single time whether he wanted to have the gamble or the sure thing. Stuphorn says the experiment confirms something other scientists have noted about gambling monkeys. Even when safe bets would have won them more juice.

Stuphorn's team suspected that this preference for long shots was linked to a small patch of brain in the prefrontal cortex. But that didn't prove these cells were affecting the monkeys' behavior.

So the researchers did another experiment that temporarily inactivated this brain area by cooling it. Then they let the monkeys continue playing the juice game.

And Stuphorn says the animals' behavior changed. They did not like the gambles anymore so much - that had the large variability. Instead, they went for gambles with - it was a smaller range of outcomes.

In other words, they took safer bets. Stuphorn says the finding adds to a body of research that is challenging an old idea about risky behavior. For a long time, people thought that this is something like a personality trait, that some people are risk takers and other people are not so risk-seeking. But this study suggests that an individual's risk preference can be changed simply by increasing or decreasing the activity in one area of the brain.

Stuphorn says that probably means our brains are constantly adjusting our desire to take risks, depending on the situation. That view is shared by Alireza Soltani who studies decision-making at Dartmouth College. Soltani says gambling monkeys probably take big risks because the stakes are so low.