Does early hardship in life keep children from becoming successful adults? It’s an urgent question for parents and educators, who worry that children growing up in difficult circumstances will fail to reach their full potential, or worse, sink into despair and dysfunction.

Social scientists have shown that these risks are real, but they also have found a surprising pattern among those whose early lives included tough times: Many draw strength from hardship and see their struggle against it as one of the keys to their later...