If you've ever found it difficult to sleep while staying in a hotel, on a friend's sofa or at the home of a, er, new Tinder acquaintance, then science may have an explanation for you.
It's to do with something called 'the first-night effect.' “Even when you look at young and healthy people without chronic sleep problems, 99 percent of the time they show this first-night effect—this weird half-awake, half-asleep state,” Yuka Sasaki from Brown University told The Atlantic.
Essentially, our bodies are hard-wired to sleep with one eye open when we're in unfamiliar environments. To show this, Susaki invited 11 volunteers to sleep at her laboratory. As predicted, they took longer to fall asleep on the first night. When they did finally drop off, researchers monitored their slow-wave brain activity and found that the participants were sleeping less deeply than usual.
Similar behavior has been found in animals including ducks and dolphins, helping keep them safe from predators. So there's a good reason for your sleepless nights, and it's not because your mate's sofa is only four foot long.