Dopamine Might Make People More Egalitarian

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Group of eight people reaching for slice of cake, close-up, overhead view
Photo: Dimitri Vervitsiotis/Getty Images

A great deal of what humans do centers on concern — or a lack thereof — with how fairly resources are divvied up. Who’s getting what, and do they deserve their share? Given that humans, lacking the physical prowess of many other species, have historically relied on generosity and ingenuity to survive, it makes sense that we’d have this preoccupation.

Now a new study in Current Biology suggests that a hit of the neurotransmitter dopamine might make individuals more sensitive to inequity in the distribution of a resource. A research team led by Ignacio Saez of UC Berkeley had study participants play various versions of the Dictator Game — more or less, “Here, take these 100 tokens worth a little money and decide how many you want to keep versus how many you want to give to an anonymous partner” — sometimes after getting a hit of tolcapone, a substance that increases the amount of dopamine sloshing around in the brain, and sometimes after getting a placebo.

The researchers found that those who got the placebo pushed a more iniquitous distribution of the tokens — those who got the dopamine, on the other hand, were fairer, and the researchers saw this effect regardless of a given participant’s feelings about inequality, which were surveyed before the experiment. This fits into previous “substantial, albeit correlational, evidence suggesting a link between dopamine” and sharing and other prosocial behaviors, the researchers write.

Saez and his team write that both this result and some associated brain simulations they ran support the idea that our brains explicitly model these sorts of issues about the distribution of rewards — we’re not just responding implicitly to social cues, to people nodding or tutting as a result of our generosity or lack thereof. Something deep in the human brain is very concerned with who is getting what, which — again — makes some intuitive sense given the social nature of our species.