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After talking to several researchers for this story, I realized the English word “want” is imprecise to describe the psychological phenomenon Leyton has been describing.
“It’s not your desire for world peace,” says Kent Berridge, a neuroscientist at the University of Michigan. “It’s not my desire to exercise or lose weight.” Those are “real desires,” he assures. But they are not behind the sort of behavior that is facilitated by the dopamine system in the brain. “They don’t give you that kind of urge.”
Imagine this scenario. You’re at a house party, sitting on a sofa. In front of you is a bowl of peanuts. Humble, roasted, salted peanuts. Not a super exciting snack. And you’re not that hungry. But in a moment of fidgetiness, you take a peanut. A few moments pass. You take another. And then another. Do you even like peanuts? You know more food — tastier food — is coming when dinner is served. You don’t really want to eat these, but now, half the peanut bowl is gone. Still, there’s something inside you — wordless, noiseless, unceasing — compelling you to reach for more.
That’s want.
It’s a manifestation of our mesolimbic system, the reward pathway in the brain that’s facilitated by dopamine. It’s a system that’s trained, over time, to influence our decisions. It’s the system that compels you toward the peanut and also toward other things, like scrolling through endless TikToks or Instagram reels.
Leyton’s cocaine experiment highlights another key, unintuitive, way to define wanting — by showing that wanting is not the same as liking.
You might find this idea confusing. Scientists were once confused by it, too. “When I started in the field decades ago, we thought they were basically the same two words for the same psychological process,” Berridge says.
It made sense to conflate the two. In daily life liking and wanting ”go together really well,” Berridge says. We want things because we like the way they taste or how they make us feel.
It just seems so obvious that liking and wanting should go together. So it’s interesting to see the studies in which they can, indeed, be pulled apart. First, there were animal studies. Starting in the late 1980s, Berridge and colleagues surgically or chemically diminished lab rats’ ability to produce dopamine.
Without dopamine, “those rats won’t eat voluntarily, they won’t drink voluntarily, they won’t pursue any reward voluntarily,” Berridge says. “And it was thought that they had lost all pleasure.” But, studies concluded, they apparently did not.
There’s convincing evidence that this split between liking and wanting happens in humans, too. That’s what Leyton’s cocaine study demonstrates — the liking of cocaine and the wanting of cocaine can be disentangled.
Leyton has repeated the dopamine-reducing experiment with other drugs, “with alcohol, tobacco,” he says. When he puts people in a low dopamine state, they don’t just say they crave their drugs less, but they’re less willing to work on a tedious computer task to obtain them.
He’s even done a version of this study with money. “It’s not a drug,” he says, “it’s not even delicious!” But when Leyton put them into a low dopamine state, participants “were less willing to sustain the effort to obtain $5 bills.”
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