We’re Still Learning about Sleep
Even after centuries (or millennia) of study, no one really knows exactly why we sleep. Just the same, researchers continue to uncover important discoveries about the mysterious phenomenon that occupies about a third of our lives.
For instance, they found that interrupted sleep is worse than short, steady sleep. Investigators say that people who experience frequent interruptions during their sleep are less happy and less energetic the next day than people who went to bed late but were able to sleep continuously for a few hours.
And it’s a myth that our hectic modern lifestyle is stealing sleep from us. People living in contemporary hunter-gatherer societies in parts of Africa and South America sleep less than 6.5 hours a night. That’s less than the average American, who gets between 7 and 8 hours.
Perhaps most interestingly, a recent study found evidence of a phenomenon in people that is most common in marine animals, like dolphins. They sleep by shutting down just half of their brain at a time. Participants in a study on sleep, on the first night that they slept in the lab, showed more activity in the left hemisphere of their brains during deep sleep than in the right hemisphere.
It’s theorized that having one hemisphere remain more "vigilant" during sleep may be a survival strategy when humans are in a new environment -- the left hemisphere may serve as a "night watch" that wakes the sleeper up if there's danger.