Learning aggression?

From Pacific Standard: "Superheroes dominate American pop culture at the moment, which would seem to be a good thing. Superman, Wonder Woman, and most of their peers fight injustice and help those in need. One would think their young fans would learn to emulate their admirable behaviors. Unfortunately, one would be wrong. That's the conclusion of a just-published study in which 240 preschoolers were evaluated at two points in time, one year apart. It found their engagement with superheroes at the first point was not related to any sort of 'pro-social or defending behavior' at the second. But the researchers found a link between identification with such characters and increased aggression over time."