Cows can sleep standing up, but they can only dream lying down.
745
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
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
Studies show that the colder the room you sleep in, the more likely you are to have a bad dream.
28