We all know the feeling: You're exhausted when you arrive at the hotel, so you try to crash early and...no dice. Your brain won't switch off. And when you do sleep, you wake up and wonder where the heck you are. It turns out that unfamiliar surroundings don't just play in to your wariness while you're awake—it happens while you're sleeping too.
Researchers at Brown University looked into the "one eye open" phenomenon for a study published in Current Biology. They used several methods to test the brain activity of subjects during two nights of sleep. They found that the first night in the lab showed heightened brain activity and alertness on one side of the brain. Translation: People were more easily woken by sounds played in one ear during deep sleep. They were also more likely to react quickly once they were awake. On subsequent nights, neither of the brain hemispheres displayed the same alertness. They were symmetrical, or, symmetrically inactive in this case.
That "asymmetry" on the first night exists naturally in other mammals. Dolphins, for example, use half of their brain during sleep to remind them to resurface to breathe. For us humans, it's a similar defense for an environment we don't completely trust—our brain is protecting us during our most vulnerable state. A big thanks for the built-in Night's Watch upstairs, but seriously, relax so we can catch some quality zzz's on vacation.
Avoid counting sheep on your next "first night" by being prepared with ways to cope. If you're stressing about the next day and can't get your mind off your to-do list, try practice mindful meditation to get in a more peaceful state. Help yourself out by eating the right foods: milk, bananas, and passion fruit (who knew) can help with sleep. Steer clear of caffeine, alcohol, and fatty foods that can make you toss and turn. Try yoga poses or stretches that can get you relaxed and ready to rest. If the damage is already done and you need to bounce back the next day, try these tips instead.