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Biology 202
2002 Second Paper
On Serendip

Gambling and the Brain

Rebecca Roth

Why do gamblers bet more after they just lost a hand? Why do investors throw good money after bad? Why do people believe that a string of losses makes a win more likely? Why do so many people say that they will win their money back in the next hand? Is part of the appeal of gambling its unpredictability? Or do we just look at it as a way to "get rich quick"? The answer to these questions may lie in the science of the brain. Some studies indicate that gamblers bet more after a loss because they are induced to fix an error. Their brains are telling them they've made a mistake and that they need to correct it (1). These studies could possibly explain other risky acts. If you ask many people why gamble, their response is "it is like a drug" (5).

Compulsive gambling is a behavior which may rely on brain circuits that evolved to help animals assess rewards important to their survival. Researchers have found that those same circuits are used by the human brain to assess social rewards. They found that the brain systems that detect and evaluate such rewards generally operate outside of conscious awareness. The study said that much of what happens in the brain goes outside of conscious awareness. There are automatic brain circuits which affect activities such as gambling (2). However, this challenges prior notions which say that people make conscious choices about their everyday decision making. If people can get themselves to work unconsciously, how does the brain really know what it must pay conscious attention to? Also, how did evolution create a brain which makes such distinctions?

Experiments performed on animals and humans are showing that the brain has evolved to shape itself according to what it encounters in the external environment. Dr. Montague, of Baylor College of Medicine said that ninety percent of what people do everyday is carried out by an autonomic unconscious system that is evolved to help creatures survive (2). According to research, we use these circuits to know what to attend to and what to ignore. Brain imaging machines directly measure the activity of human brain circuits. The two circuits that have been studied most extensively are involved in how we assess rewards. The chemical dopamine is used in these two circuits. The first circuit is in the middle of the brain and helps us assess rewards. Learning takes place only when something unexpected happens and dopamine firing rates increase or decrease. When nothing unexpected happens, the dopamine system is quiet. In humans, the dopamine signal is sent to a higher region of the brain, the frontal cortex. The anterior cingulate is located in part of the frontal cortex and part of its function is detecting errors and conflict in the flow of information being processed automatically. Brain imaging shows that when a person gets an unexpected reward, more dopamine reaches the anterior cingulate. However, when a person expects a reward and does not get it, less dopamine reaches that region. Also, when a person expects a reward and gets it, the anterior cingulate is quiet (2). From these observations it looks like winning in gambling can affect the dopamine system, similar to the neural circuitry involved in the highs and lows of abusing drugs. Therefore, people can become addicted to gambling too. Do compulsive gamblers have vulnerable dopamine systems? The first win would be a dopamine rush, but does that then get embedded in their memory? According to the study, gamblers keep gambling and the occasional dopamine rush of winning overrides their conscious knowledge that they will lose in the long run (2).

A research team headed by Dr. Hans C. Breiter used magnetic resonance imaging to map the brain responses of twelve men while they participated in a game of chance involving winning or losing money. The tests were divided into two stages -- expectancy and outcome. During the expectancy phase, the subjects were shown how much money they could potentially win, depending on where the arrow stopped on a spinning disk. During the outcome phase, the arrow stopped on a designated monetary value on the disk, and the subjects found out whether they had won or lost money on that spin. This experiment showed that blood flow to the brain changed in ways similar to that seen in other experiments where an infusion of cocaine is given to cocaine addicts. Similar changes in blood flow to the brain occur when low doses of morphine are given to drug-free individuals. The changes varied in accordance with the amount of money involved, and a broadly distributed set of brain regions were involved in anticipating a win. The more money involved, the more excited the person became. The primary response to winning, or the prospect of winning, was seen in the right hemisphere of the brain, while the left hemisphere was more active in response to losing (3). This similarity suggests that common brain circuitry is used for various types of rewards (4). This study is also important because identifying regions of the brain and then mapping the neural pathways that process the anticipation and rewards could possibly lead to the development of medications or interventions that could block these circuits and provide other treatment approaches.

William Gehring, of the University of Michigan, and his colleagues, used an EEG to monitor the brain waves of experimental subjects as they played a gambling-type game. There were twelve subjects who played a video game in which they had to choose two numbers: 5 and 25. If they picked 5 and it won; they would get five cents. If 5 lost, they would lose that amount and so forth. Choosing the 25, would result in a gain or loss of 25 cents. He found that when people lost either amount, the anterior cingulate would become active within a quarter of a second. In the next round after a loss, subjects almost always chose the 25 (1). Choices made after losses were riskier and were associated with greater loss-related activity than choices made after gains (7). Subjects could have been gambling more because the brain was expecting them to win. However, we should keep in mind that his subjects were paid enough so that they could not leave with less money then they came with (1). Another problem with this study is that people tend to gamble more freely with money that is not their own. I can go to Atlantic City, walk around, watch others gamble, and not even spend a nickel. However, when I go with my grandparents who give me money, I am ready, willing, and able to gamble. I always try to win the money back that I lost. I also know that if I play a gambling game on my computer, I bet large sums of money since I know it is not real. Another problem with Gehring's experiment was the small amount of money that was involved. If we were talking about gambling in Las Vegas or in Atlantic City, the stakes would be much higher. Then again there is the other side, in which people become more averse to loss after they lose a lot of money. It happens to my friends when they bet on a sporting event. If their team loses, they are more cautious the next time.

A challenge for the future is to determine how different parts of these brain circuits affect the thinking, emotion and motivation involved in anticipation, evaluation, and decision-making. The findings in these studies show how the brain evaluates the choices made. Neuroscience may provide new constructs for understanding economic decision-making. An interesting topic for future research would be to look at how people play the stock market.

If we continue to look at unconscious reward circuits in human behaviors we may be able to understand why people act the way they do. Are we processing information at the unconscious level? That may scare many people since we look at most of our decisions and behavior as conscious decisions. We want to believe that we are fully aware of the choices that we make. Ongoing research will help us look more closely at systems that process reward and organize behavior in humans. Further research might help us try to determine the roles played by the different components of brain circuitry. This in turn may help scientists understand the development of drug abuse and compulsive gambling. If we know the cognitive processes related to gambling, we can understand compulsive gambling better and give those people the treatment that they need.


1)Brain may dictate raising the stakes, Philadelphia Inquirer , Philadelphia Inquirer Newspaper article

2)Hijacking the brain circuits with a nickel slot machine, NY Times, NY Times Newspaper article

3)Gambling has drug-like effect on brain,USA Today Newspaper article

4)Gambling—Like Food and Drugs—Produces Feelings of Reward in the Brain , Scientific American

5)You Bet Gambling Is Addictive , Business Week Online

6)The Good, the Bad, and the Anterior Cingulate, Science Journal, Science Magazine

7)The Medial Frontal Cortex and the Rapid Processing of Monetary Gains and Losses, Science Journal, Science Magazine

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