Have you ever noticed that waking up after the first night sleeping in an unfamiliar setting, such as a hotel while on a business trip or on vacation, you find yourself feeling groggy and somewhat disoriented? It would be easy to assume that this phenomenon was nothing more than the manifestation of jet-lag, however experts have discovered a that it is actually the result of a phenomenon called the ‘First Night Effect.’

Numerous studies have been completed assessing the concept of the ‘first night effect’ among different age groups, racial groups, and lifestyles, allowing scientists to determine that there is no one group that is prone to experience it. In fact, it appears to be common among anyone who is sleeping in an area outside of their normal setting.

Interested not only in the existence of this phenomenon, but in actually understanding why this was taking place, sleep scientist Masako Tamaki and a team of colleagues from Brown University decided to further research what was actually occurring within the human brain when people are experiencing this effect. Using advanced neuroimaging techniques, the scientists analyzed the brain activity in their participants while they were sleeping, watching for any anomalies that may occur only when one is sleeping in an unfamiliar area.

What they discovered was that one side of the brain actually remains awake!

Experts believe that this is a form of self-preservation that has been biologically wired into us. When we are sleeping in an area that we are not familiar with, the side of the brain that remains awake allows us to be woken easier in the event that we hear any type of ‘deviant’ sounds, such as the cries of an unidentified animal or the footsteps of someone approaching. While nothing more than an annoyance today, as you attempt to catch up on your sleep in a hotel room, this evolutionary adaptation would have proven incredibly useful when our ancestors were in far less secure locations.

For those that travel for a living, Dr. Yuka Sasaki, one of the researchers, has good news: “Human brains are very flexible. Thus, people who often are in new places may not necessarily have poor sleep on a regular basis.” She also suggests that travelers can reduce the effect of first night effect by bringing their own pillows with them, or by staying in hotels that provide similar accommodations to what they are already used to.