為什么在新環(huán)境難以入睡？

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If you're at a relative's house for the holiday， getting quality sleep on the first few nights can be a challenge. Maybe you're away on a contest and you've got a big presentation the next morning; maybe it's your first night in a new home after a long day moving boxes. Whatever the circumstances， you could really need a good night's rest-but， given that you're sleeping in a new place， that may be easier said than done. In a 2016 study， scientists at Brown University found a cause for this first-night effect （FNE）： constant， animal-like vigilance.

Sleep is something of a puzzle for scientists. Most animals do it， but it's not entirely clear why it's necessary. In survival terms， it's pretty inconvenient for an animal to be off its guard for several hours every day. But rather than evolving to live without rest，some animals have developed the ability to sleep with one eye open. Bottlenose dolphins，southern sea lions， domesticated chickens， and beluga whales are among species that practice unihemispheric slow-wave sleep （USWS）， in which just one half of the brain sleeps at a time.

如果你度假的時(shí)候在親戚家借宿，頭幾晚想要獲得優(yōu)質(zhì)睡眠可能會(huì)是個(gè)挑戰(zhàn)。（剩余1500字）