Dopamine and Future Forecasting

Ed Yong has a typically excellent post on a new paper that looks at how manipulating dopamine levels in the brain can change our predictions of future pleasure:

Tali Sharot from University College London found that if volunteers had more dopamine in their brains as they thought about events in their future, they would imagine those events to be more gratifying. It's the first direct evidence that dopamine influences how happy we expect ourselves to be.

Sharot recruited 61 volunteers and asked them to say how happy they'd feel if they visited one of 80 holiday destinations, from Greece to Thailand. All of the recruits were given a vitamin C supplement as a placebo and 40 minutes later, they had to imagine themselves on holiday at half of the possible locations. After this bout of fanciful daydreaming, they had to take another pill but this time, half of them were given L-DOPA instead of the placebo. Again, they had to imagine themselves in various holiday spots.

The next day, Sharot brought the volunteers back. By this time, they would have broken down all the L-DOPA in their system. She asked them to choose which of two destinations they'd like to go to, from the set that they had thought about the day before. Finally, they rated each destination again.

By the end of the experiments, they perceived their imaginary holidays to be more enjoyable if they had previously thought about the locations under the influence of L-DOPA (while vitamin C, as predicted, had no effect). The implication is clear: think about the future with more dopamine in the noggin and you'll imagine that you have a better time.

As I've noted before, the popular caricature of dopamine - it's the hedonistic molecule in the brain, activated by sex, drugs and rock and roll - is slightly misleading. Dopamine neurons, it turns out, don't care about pleasure per se - they're much more interested in predicting pleasure, and then comparing our predictions to the actual event. The transactions of dopamine are largely about learning - finding a way to maximize our rewards - and not about mere decadence.

What I find so interesting about this experiment is that it neatly confirmed this theory of computational neuroscience. After all, the subjects didn't feel happier after popping a pill of L-DOPA - boosting dopamine levels didn't lead to instant gratification, like Huxley's soma. Instead, it merely altered their predictions of future happiness.

But here's the funny thing about those predictions: they tend to correlate pretty accurately with our actual experience. If you think you're going to have a good time on vacation, then you probably will, just as we tend to enjoy foods and beverages and products that we expect to enjoy. (This is the consumer version of the placebo effect.) Here's how I described similar phenomena in How We Decide:

Baba Shiv, a neuroeconomist at Stanford, supplied a group of people with Sobe Adrenaline Rush, an "energy" drink that was supposed to make them feel more alert and energetic. (The drink contained a potent brew of sugar and caffeine which, the bottle promised, would impart "superior functionality"). Some participants paid full price for the drinks, while others were offered a discount. The participants were then asked to solve a series of word puzzles. Shiv found that people who paid discounted prices consistently solved about thirty percent fewer puzzles than the people who paid full price for the drinks. The subjects were convinced that the stuff on sale was much less potent, even though all the drinks were identical. "We ran the study again and again, not sure if what we got had happened by chance or fluke," Shiv says. "But every time we ran it we got the same results."

Why did the cheaper energy drink prove less effective? According to Shiv, consumers typically suffer from a version of the placebo effect. Since we expect cheaper goods to be less effective, they generally are less effective, even if they are identical to more expensive products. This is why brand-name aspirin works better than generic aspirin, or why Coke tastes better than cheaper colas, even if most consumers can't tell the difference in blind taste tests. "We have these general beliefs about the worldâ¯for example, that cheaper products are of lower qualityâ¯and they translate into specific expectations about specific products," said Shiv. "Then, once these expectations are activated, they start to really impact our behavior.

So the next time you buy something on sale, pop a pill of L-DOPA. It will increase your pleasure, if only because you expect it to.