The Neuroscience of Gambling

This is just sad:

Harrah's New Orleans, the largest casino in the city, is on pace for its best year ever: gambling revenue is up 13.6 percent through the first five months of 2007 compared with the same period in 2005, pre-Katrina.

The casinos in this region are generating more revenue -- from significantly fewer players -- in large part because of the extra money that many area residents have in their pockets and fewer alternatives on where to spend it, casino executives and others in the region say.

I sometimes wonder if, one day, we'll view casinos as we currently view cigarettes: a dangerous consumer product that encourages addiction and self-destructive behavior. Sure, gambling is fun (and cigarettes taste great after a big meal), but the product dangerously manipulates our brain.

Why is gambling so seductive? Why do people flock to Vegas or New Orleans or the nearest Indian Reservation to lose money? The answer depends, in large part, on our dopamine neurons. Much of our understanding of the dopaminergic system comes from the pioneering research of Wolfram Schultz, a neuroscientist at Cambridge University. He has spent the last few decades measuring the firing rates of dopamine neurons in the brains of monkeys as they are receiving rewards of fruit juice. His experiments observe a simple protocol: Schultz sounds a loud tone, waits for a few seconds, and then squirts a few ounces of juice into the monkey's mouth. At first, the dopamine neurons don't fire until the juice is delivered. The cells are responding to the actual reward. However, once the animal learns that the tone precedes the arrival of juice - this only requires a few trials - the same neurons begin firing at the sound of the tone instead of the sweet reward. Schultz calls these cells "prediction neurons," since they are more concerned with predicting rewards than with the rewards themselves. (This process can be indefinitely extended: the dopamine neurons can be made to respond to a light that predicts the tone that predicts the juice, and so on.) Once this simple pattern is drilled into the monkey's dopamine neurons, it becomes exquisitely sensitive to variations on the pattern. If, for example, the pattern is violated - if the tone is played but the juice never arrives - then the monkey's dopamine neurons start to fire at a very low rate. This is known as the "error signal". However, if the monkey gets some unexpected juice, then the neurons fire with ecstatic enthusiasm. There is nothing better than a surprising reward.

Now back to gambling. Think of a slot machine.* You put in a coin and pull the lever. The reels start to whirr. Pictures of cherries and diamonds and sevens fly by. Eventually, the machine settles on its verdict. Since slot machines are programmed to return only about 90 percent of wagered money, chances are you lost money. Nobody beats the software code.

Think about the slot machine from the perspective of your dopamine neurons. The purpose of these cells is to predict future rewards. When you are gambling, your neurons are struggling to decipher the patterns inside the machine. They want to understand the game, to decode the logic of luck.

But here's the catch: slot machines can't be solved. They use random number generators to determine their payout. There are no patterns or algorithms or streaks to uncover. There is only a stupid little microchip, churning out arbitrary digits.

At this point, our dopamine neurons should just surrender. They should turn themselves off: the slot machine is a waste of mental energy. But this isn't what happens. Instead of getting bored by the haphazard payouts, our dopamine neurons become obsessed. When we pull the lever and get a reward, we experience a rush of pleasurable dopamine precisely because the reward was so unexpected. (The clanging coins are like a surprising squirt of juice. It's operant conditioning gone bezerk.) Because our dopamine neurons can't figure out the pattern, they can't adapt to the pattern. The end result is that we are transfixed by the slot machine, riveted by the fickle nature of its payouts.

This cellular mechanism helps explain why Parkinson's patients on dopamine agonists - a drug that imitates the activity of dopamine in the brain - are at serious risk for gambling addictions. For these people, the surprising rewards of the casino are simply too rewarding. Scientists have demonstrated that dopamine agonists strongly bind to the same brain regions ordinarily activated by gambling. As a result, each stroke of good fortune triggers a massive release of chemical bliss. These patients are blinded by the pleasure of winning, even as they slowly lose everything.

Obviously, there are other factors at work in the casino besides dopamine. (The free booze certainly helps.) But games of chance have been brilliantly designed to take advantage of this ancient cellular pathway in the brain. The evil genius of cigarettes is that they make us crave toxic smoke. The evil genius of the casinos is that they've figured out a way to make us want to lose money.

*Slot machines account for about 70 percent of the $48 billion spent in America on gambling each year, which means that the average American spends five times more on slot machines than on movie tickets. There are now twice as many slot machines in America as ATM's.