Teenagers are less likely to cooperate than adults, and it's not just about their brains
Teenagers have long been known to be less cooperative than adults. New research now reveals what is going on inside: it's not simply that they are worse at reading other people, they also tend to put their own interests first.
The study, published in eLife, had young people and adults play a repeated prisoner's dilemma, a classic game-theory experiment in which you choose between cooperating and acting in your own interest at the other player's expense. Cooperation pays off more for both sides, but it requires trust. Teenagers cooperated consistently less, even after positive experiences with the other player. That suggests the issue is not just a lack of ability, but also one of motivation.
Until now, reduced cooperativeness in adolescents had largely been attributed to immature mentalizing: the ability to model other people's thoughts and intentions. The prefrontal cortex, the brain region responsible for this, does not fully mature until around age twenty-five. But the new study adds another layer: even when teenagers were capable of recognizing a partner's cooperative intent, they more often chose to prioritize themselves. The internal calculation is different, not just the capacity.
What this tells us about adolescent behavior
That distinction has real implications for how we think about risk-taking and social decision-making during adolescence. If the problem were purely one of brain immaturity, providing more information or raising awareness might be enough of an intervention. If self-interest is an independent factor, that calls for a different approach: creating contexts in which cooperation feels more natural, or making its benefits more concrete and immediately visible.
The study also found that teenagers reacted more strongly to a partner who had previously refused to cooperate. If someone had let them down even once, they were considerably more likely to stop cooperating afterward. Adults bounced back from such episodes more readily. That pattern may point to a heightened sensitivity to social rejection or loss in adolescents, something consistent with what we already know about teenage behavior, but now supported by a clearer mechanistic account.
Why this matters for longevity
At first glance, this seems far removed from aging research. But social connectedness and the quality of social relationships are among the best-documented predictors of healthy, long life. The willingness to cooperate, and the brain biology driving it, begins to take shape during adolescence. Understanding that development may help explain why some people are more socially integrated later in life than others, and what mechanisms underlie that difference.