Teenagers cooperate less than adults — and it is not just about brain development
Adolescents have long been known to cooperate less than adults. New research now reveals what is happening internally: it is not only that they are worse at reading others — they also…
The study, published in eLife, had adolescents and adults play a repeated prisoner’s dilemma — a classic game theory experiment in which players choose between cooperating or defecting for personal gain at the other player’s expense. Cooperation produces the best combined outcome, but requires trust. Teenagers cooperated less systematically, even after positive experiences with the other player. That suggests the issue is not only capability, but motivation.
Previously, reduced cooperation in adolescents was largely attributed to underdeveloped mentalizing — the ability to model the thoughts and intentions of others. The prefrontal cortex, the brain region responsible for this, does not fully mature until around age 25. But this study adds a layer: even when teenagers were capable of recognising a partner’s cooperative intent, they more often chose to prioritise themselves anyway. The internal calculation differs, not only the cognitive ability to make it.
What this says about adolescent behaviour
This distinction matters for how we think about risky and social decision-making in adolescence. If reduced cooperation were purely about neural immaturity, providing more information or raising awareness would be sufficient. If self-interest operates as an independent factor, different approaches are needed — creating contexts where cooperation feels more natural, or where its benefits are more immediate and concrete.
The study also found that teenagers responded more strongly to prior defection by their partner. A single instance of being let down made them substantially less likely to cooperate afterwards. Adults recovered from such episodes more readily. This pattern may reflect a heightened sensitivity to social rejection or loss in adolescence — consistent with existing knowledge of teenage behaviour, but now supported by more precise mechanistic evidence.
Why this matters beyond adolescence
Social connectedness and the quality of social relationships are two of the most robustly documented factors for healthy aging and longevity. The willingness to cooperate — and the brain biology that drives it — begins taking shape during adolescence. Understanding that developmental trajectory may help explain why some people are more socially integrated in later life, and what mechanisms underlie that difference. The seeds of social health in old age are planted earlier than researchers have often assumed.