Monkey Research Shows How Gambling Depends on Neurology

Johns Hopkins Gambling Research - Rhesus Monkeys Betting Study

The research showed that Rhesus monkeys tend to be risk takers, but a simple change in neurological signals can make them more risk-averse.

Rhesus monkeys are small intelligent mammals found throughout central, south, and southeast Asia. However, the Rhesus monkey known as Aragorn has a skill that sets apart from all other monkeys. He is a practiced gambler.

Researchers at Johns Hopkins University taught monkeys how to gamble, then studied how their gaming behaviors compare and contrast with human gambling. Then they changed how the monkeys received signals, which changed their level of risk taking.

Scientists taught a group of Rhesus monkeys to gamble, with drinks of waters as the stakes in the game.

Aragorn was a part of a group of monkeys at Johns Hopkins University, all of which are named after ‘Lord of the Rings’ characters. Neuroscientist Veit Stuphorn has trained Aragorn and his fellow monkeys to perform what scientist refer to as “decision-making under risk.

“Decision Making Under Risk”

The purpose behind the study is to see how those choices unfold in the brain. In doing so, Dr. Stuphorn showed that an area of the brain is specifically associated with high-risk tendencies. Stuphorn believes that this finding could eventually help scientists better understand these tendencies in humans.

Aragorn was the first monkey in the study, which began nearly decade ago. The study does not involve poker or blackjack specifically, however, the research is illustrative and beneficial when it comes to understanding gambling.

How the Monkey Research Is Done

When training the monkeys, the Johns Hopkins researchers started by introducing both color schemes and probability to the game. Once the monkeys can comprehend that decision making leads to results and relative benefits, then places the monkey in front of a computer screen. They are then shown two square boxes: one on the left and one on the right.

Both boxes are the same size. Each box contains a different color: either red, blue, green, or cyan (a blue-green color). The level of color corresponds to increasing rewards. In this challenge, the reward is water. The probability of a particular payoff is determined by the proportion of the colors in the box.

The example Stuphorn used was this: a box that is all-blue guarantees a medium amount of water. A box that is 80% cyan and 20% green indicates that there is a high chance of getting small amounts of water, but a low chance of getting a large amount of water. Once shown the two boxes, the monkey then must decide between the two options.

Monkeys Use Eye Movements to Gamble

Researchers use sensors to track the monkeys eye movement. Dr. Stuphorn said, “The monkey used his eyes to make the choice.”

The sensors can see which box its gaze fixes on, which in this case indicates the animal’s choice. The monkey then receives an appropriate reward for its selection. If it was a good gamble, the monkey receives more water. If it was a bad gamble, the monkey receives less.

The Johns Hopkins researchers run the trial until the monkeys either gets full of water or gets bored. Stuphorn said that its often very clear when they have lost interest. Stuphorn quipped, “They close their eyes and snore.”

Rhesus Monkeys Are Risk Takers

After continuous trials, Stuphorn and his colleagues determined that the monkeys are risk-takers. They would consistently choose to gamble for more water over settling for less. Researchers speculate that risk taking led to certain Rhesus monkeys collecting more food, thus becoming stronger and more likely to pass on the traits of a risk taker.

Originally, Stuphorn and other researchers performed the same research, then compared notes to determine their findings were the same. Five years ago, Stuphorn and then-Hopkins graduate student Xiaomo Chen joined their efforts and decided to take the study to the next level. The scientists moved their focus to the brain’s frontal cortex, known as the supplementary eye field (SEF). This area helps to control movement which, displayed by their previous research, might play a role in risky behavior.

Previous studies, however, gave unclear details. So. In order to paint a clearer picture, they wanted to test what would happen if they deactivated the supplementary eye field. Stuphorn noted that the process is completely harmless and reversible.

Aragorn and Isildur: A Study in Risk Taking

The researchers worked with Aragorn and another monkey named Isildur. Tiny metal plates were placed over the SEF region of the monkey’s brain. It would then cool the tissue until it became inactive. Stuphorn said, “If it really has an impact, the behavior of the monkey should change.”

Once the SEF was inactive, the monkey’s behavior changed. Aragorn and Isildur suddenly became more prone to make safer bets and much less likely to opt for riskier choices.

Dr. Stuphorn added, “The preference for the uncertainty was reduced. This study definitely helps in understanding what this brain area is doing.”

Risk/Reward Factor Might Change Results

A comparative psychologist as the Florida Institute of Technology, Darby Proctor, mentioned that it was “not super surprising” that the frontal cortex plays a role in the decision-making process. Though not involved directly with the study, Proctor has done similar work with primates.

“That’s where we know that humans make their complex decisions,” said Dr. Proctor.

“But I think it’s very interesting that they are able to change the responses by knocking out some of those regions. That helps us really to refine where the biological basis for those decisions are.”

Dr. Proctor noted that during the trial, there was little at stake for the two monkeys involved. If the rewards had been more drastic, the results may have varied more.

How Neurology Affects Gambling Decisions

Dr. Stuphorn mentioned that his gambling research, though it has revealed a lot, has not given definitive answers yet. The SEF controls eye function only, but not motor movements. He also suggests that the inactivating process would have no effect on other casino games, such as slots. Such games rely on arm movement, which is under the control of a different part of the brain.

A neuroscientist at Yale University, Daeyeol Lee, stressed the importance of the study and that it should not be underestimated. He believes that a wider detailed result of the researcher’s work could be revealed, if the cooled area was possibly expanded. Dr. Lee noted that other areas of the brain close to the SEF are known to control limb function, which caused the Yale University researcher to speculate “these areas all have similar properties.”

The Johns Hopkins researchers said the key finding in the study is how dependent risk taking can be on circumstances. He said, “People thought of risk-taking as a character trait of the person… that some people are risk-taking and others are not. Now, people think of risk-taking as more flexible.”

Stuphorn and Chen hope the results and details from further studies provide research that helps the way scientists view primate, and in turn human, perceptions of risk.