Are you familiar with sleep inertia?
It's that groggy, slow feeling when you first wake up. According to a study, that blurry feeling you have when you first wake up is kind of like being drunk.
Complex Thinking
The feeling sometimes only lasts a few minutes, but its effects can linger for a few hours. The study tested the problem-solving abilities of people who had just awakened from eight hours of sleep.
It turns out that the subjects performed most poorly during the first three minutes after waking up. There's some evidence suggesting that the areas of the brain in charge of problem solving and complex thought take longer to wake up than other parts.
This might sound like a minor inconvenience or something not worth studying, but if you're a doctor or firefighter or anyone who might have to wake up suddenly and snap into action, sleep inertia is a bigger deal.
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Published online 2016 May 18. doi: 10.2486/indhealth.2015-0236