A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
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Sleeping on the job is acceptable in Japan. It is viewed as exhaustion from working hard. Some people fake it to look committed to their job.
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In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
The average person falls asleep in seven minutes.
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47% of people have a nightmare at least once a month.
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