Turns out, part of your brain is always keeping watch.
“Did you sleep alright?” This question, often directed at houseguests over the breakfast table, isn’t just common courtesy; turns out, it’s rooted in science.
For over 50 years, the Atlantic reports, sleep scientists have known that people don’t snooze as soundly as they normally would during their first night in a new environment. Data from this “adaptation night” was normally discounted, and no one really looked into the why.
That is until now: In hopes of better understanding this “first-night effect,” Brown University researchers monitored 35 volunteers sleeping on makeshift beds, a.k.a. medical scanners measuring brain activity. Recruits also had electrodes attached to their heads and hands in order to track brain waves, eye movements and heart rate.
Researchers found that subjects took longer to fall asleep and slept less deeply on the first night because part of the brain’s left hemisphere remained more active than in the right hemisphere. That region of the brain also responded faster to noise stimuli such as a beep played through headphones.
The behavior isn’t unlike that of animals. Seals, for example, who sleep normally on land, sleep with one eye open looking down when they’re at sea. Researchers speculate that the “first-night effect” is an adaptive response meant to protect us when we’re in a new and strange environment.
Most people return to their normal sleep habits on night two. In other words, give it another night before phoning housekeeping to request a better pillow.