This article originally appeared on VICE US
You know that feeling when you're staying in an Airbnb, and even though the place has good vibes, and the host magnanimously proffered her best linens, and even though the blinds are good at blocking out all light, somehow you still find yourself listening to your host's refrigerator and contemplating death at 3 AM as you wait for the warm blankness of sleep to return? It looks like science has an explanation for that.
According to a new report in the journal Current Biology, you're not suddenly an insomniac; your brain just won't shut completely off so that you'll be capable of "faster responses to risk factors" that you may not yet know about in these unfamiliar environs.
The report comes from the findings of an experiment by a team including Yuka Sasaki of Brown University, who, like all scientists in their field, were plagued by the notorious and well-documented first night effect in lab science. That is: participants in lab studies all sleep horribly the first night, and it wreaks havoc on the reliability of experimental data.
Turns out what's happening is that one hemisphere of a participant's brain is significantly more active on night one in a new sleeping space. Consequently, response time to a "deviant sound" was quicker on the first night of the experiment. The team determined this by having sleeping subjects wiggle their fingers when the "deviant sound" was played.
The report doesn't explain how the sound was "deviant," but presumably it was a bullwhip striking a buttock—that would make me wiggle my fingers.
"Unilateral hemispheric sleep" according to the report, has an established connection to avoidance of predators in other animals like birds. As NPR noted, a German experiment from 1999 looked at the brains of ducks sleeping in groups, comparing ducks surrounded by other ducks, to ducks at the edge of the group who were half-exposed to potential attacks from the side. Fully-surrounded ducks were able to shut off their whole brains, while ducks at the edge kept half of their brains on, and their gazes fixed on the non-duck side. The report concluded that the ducks sleeping with one eye open were scanning for shotgun-wielding Elmer Fudds.
"When we're sleeping in a new environment and we don't know how many predators are around," Niels Rattenborg of the Max Planck Institute for Ornithology told NPR, "it would make sense to keep half the brain more alert and more responsive to bumps in the night."
So next time you're half-awake in the arms of your snoring one-night stand, one bloodshot eye darting around their shitty apartment, maybe take a break from being mad at yourself for not sleeping well, and thank millions of years of evolution for making sure you're not being devoured by wolves at that exact second.
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