Sigmund Freud thought dreams were a window into our unfulfilled sexual desires. But the dreams of video game players suggest they have a more practical role: helping us to learn new skills.

"It really looks like if you're not dreaming about it, you're not getting better," says Robert Stickgold of Harvard Medical School, who carried out one of the video game studies.

The studies don't prove that dreaming about games makes players better. But they strongly suggest that dreaming and learning are intertwined.