But there was a different pattern when it came to the social problems. Once again the preschoolers were more likely to give the creative explanation than were the 6-year-olds or adults. Now, however, the teenagers were the most creative group of all. They were more likely to choose the unusual explanation than were either the 6-year-olds or the adults.

Why does creativity generally tend to decline as we age? One reason may be that as we grow older, we know more. That’s mostly an advantage, of course. But it also may lead us to ignore evidence that contradicts what we already think. We become too set in our ways to change.

Relatedly, the explanation may have to do with a tension between two kinds of thinking: what computer scientists call exploration and exploitation. When we face a new problem, we adults usually exploit the knowledge about the world we have acquired so far. We try to quickly find a pretty good solution that is close to the solutions we already have. On the other hand, exploration — trying something new — may lead us to a more unusual idea, a less obvious solution, a new piece of knowledge. But it may also mean that we waste time considering crazy possibilities that will never work, something both preschoolers and teenagers have been known to do.

This idea suggests a solution to the evolutionary paradox that is human childhood and adolescence. We humans have an exceptionally long childhood and prolonged adolescence. Why make human children so helpless for so long, and make human adults invest so much time and effort into caring for them?

The answer: Childhood and adolescence may, at least in part, be designed to resolve the tension between exploration and exploitation. Those periods of our life give us time to explore before we have to face the stern and earnest realities of grown-up life. Teenagers may no longer care all that much about how the physical world works. But they care a lot about exploring all the ways that the social world can be organized. And that may help each new generation change the world.