Sleeping on your stomach can induce weirder, scarier, and sexier dreams.
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You forget 90% of your dreams.
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Dieters who sleep more take off more fat that those who sleep less.
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Bats sleep 18-20 hours per day.
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Cows can sleep standing up, but they can only dream lying down.
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A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
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Some people have a "natural alarm clock" allowing them to wake up when they want. This is actually caused by a burst of the stress hormone adrenocorticotropin.
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