Popular culture, following some early attempts at sleep science, likes to classify people as either night owls or early risers, depending on what time they prefer to wake up and go to sleep, and what hours of the day they feel are most productive.

Now, a study out of Russia concludes there are two other common sleep types: those who are most productive at the start and end of the day but feel sluggish during the middle hours, and those who get work done during the day but struggle in the morning and at night.

Of the 130 people who were asked to stay awake for twenty four hours straight, "[t]here was a 'high energetic' group of 25 people who reported feeling relatively sprightly in both the morning and evening; and a 'lethargic' group of 32 others, who described feeling relatively dozy in both the morning and evening."

In her interview, sleep scientist Shelby Harris gives Big Think an introduction to sleep, which she says is hardly a period of inactivity for the brain: during a normal night's sleep, the brain cycles through various stages including REM sleep, during which the brain is just as active as when it is awake.

Read more at the Atlantic

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