We spend a large portion of our lives sleeping. That might seem like an evolutionary disadvantage, given sleep leaves us immobile and potentially vulnerable to attacks for hours on end — but evidence suggests we have many key physiological functions tied to sleep, and disruptions in sleep are linked to a wide range of health problems, including a higher risk of death.

What's more, as we sleep, we often dream. In this way, sleep unlocks an experience that we can't access during our waking hours.

In the quiz below, test your knowledge of the science of sleeping, as well as the dreams that unfold during sleep. Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button, and let us know your score in the comments.

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