A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Bats sleep 18-20 hours per day.
5
People who sleep late have more mental stamina and can outperform early risers.
33
Studies show that the colder the room you sleep in, the more likely you are to have a bad dream.
28
The human brain is more active during sleep than during the day.
28
The higher someone’s I.Q. the more likely they are to be sleep deprived.
29