In one project, the company asked separate groups of boys and girls to build a LEGO castle. While both groups worked together to build the castle, they took different approaches to play afterward.

For example, the boys immediately grabbed the figures, the houses, and the catapults and started having a battle, McNally recalled, noting that the boys used the castle as a backdrop for their play.

On the other hand, the girls were more focused on the castle itself.

"They all looked around inside the castle and they said, 'Well, there's nothing inside,'" McNally said. "This idea of interior versus exterior in the orientation of how they would then play with what they built was really interesting. If you think about most of the LEGO models that people consider to be meant for boys, there's not a whole lot going on in there. But [the girls had] this idea of, 'There's nothing inside to do.'"