Anthony Pellegrini, a professor of early childhood education at the University of Minnesota, defines the kind of rough-and-tumble play that boys favor as a behavior that includes “laughing, running, smiling, jumping, open-hand beating, wrestling, play fighting, chasing and fleeing.” This kind of play is often mistakenly regarded as aggression, but according to Pellegrini, it is the very opposite. In cases of schoolyard aggression, the participants are unhappy, they part as enemies, and there are often tears and injuries. Rough-and-tumble play brings boys together, makes them happy, and is a critical party of their social development.

Researchers Mary Ellin Logue (University of Maine) and Hattie Harvey (University of Denver ) agree, and they have documented the benefits of boys’ “bad guy” superhero action narratives. Teachers tend not to like such play, say Logue and Harvey, but it improves boys’ conversation, creative writing skills, and moral imagination. Swedish boys, like American boys, are languishing far behind girls in school. In a 2009 study Logue and Harvey ask an important question the Swedes should consider: “If boys, due to their choices of dramatic play themes, are discouraged from dramatic play, how will this affect their early language and literacy development and their engagement in school?”

What about the girls? Nearly 30 years ago, Vivian Gussin Paley, a beloved kindergarten teacher at the Chicago Laboratory Schools and winner of a MacArthur “genius” award, published a classic book on children’s play entitled Boys & Girls: Superheroes in the Doll Corner. Paley wondered if girls are missing out by not partaking in boys’ superhero play, but her observations of the “doll corner” allayed her doubts. Girls, she learned, are interested in their own kind of domination. Boys’ imaginative play involves a lot of conflict and imaginary violence; girls’ play, on the other hand, seems to be much gentler and more peaceful. But as Paley looked more carefully, she noticed that the girls’ fantasies were just as exciting and intense as the boys—though different. There were full of conflict, pesky characters and imaginary power struggles. “Mothers and princesses are as powerful as any superheroes the boys can devise.” Paley appreciated the benefits of gendered play for both sexes, and she had no illusions about the prospects for its elimination: “Kindergarten is a triumph of sexual self-stereotyping. No amount of adult subterfuge or propaganda deflects the five-year-old’s passion for segregation by sex.”