Have you ever felt tired, restless or groggy after what you thought was a full night’s rest in a new place? Or perhaps jumped out of a hotel bed fully-awake at the slightest disturbance?  A new study explains that this might be because your brain just pulled an all-nighter of guard duty — half of your brain that is.

The phenomenon is called interhemispheric asymmetry and it was first observed by scientists studying the first-night effect (FNE) in the sleeping patterns of  11 people over the course of two nights. FNE is something we have all experienced, when we have troubling sleeping well in a novel or unfamiliar environment, and until now, scientists have long considered this a normal and typical sleep disturbance.