Many of us have had this experience: we lie down in a bed other than our own, perhaps at a friend's house or in a hotel room, and find it difficult or impossible to fall asleep. Is it because the bed is uncomfortable? Maybe, but perhaps there can be other reasons.
According to a new study published in Current Biology, a significant reason is what the scientists call "first night effect". They believe that one side of the brain acts as a "night watch" to warn us about potential dangers. It forces us to stay awake on the first night in a new environments.
For the study, 35 young volunteers were asked to sleep in a sleep lab for several days. Meanwhile, researchers watched their brain activities.
According to the researchers, on their first night, the left brain was more active than the right brain and people had a hard time sleeping. However, left-brain activities decreased as days went by, falling even to the point of complete calm. In this process, the participants got an increasingly better sleep experience.
The findings suggest that the different rhythms of the sides of the brain affect our sleep. When the two sides work differently, the balance between them is broken. Thus, the brain can't relax and is sensitive to anything strange in the surroundings, just as it is in the daytime.
"At some level, the brain is continuing to analyze things, even though you are not aware of the analysis, " US professor Jerome Siegel told Smithsonian
"If something unusual happens - if a door opens or you hear a key in a lock --you can be alert, even though the intensity of the stimulus (刺激强度) is quite low." More surprisingly, this phenomenon is similar to the way some animals sleep.
The researchers think that it is the result of evolution (进化), and works to protect us in potentially dangerous environments.
If you have ever had what you think is "first night effect", researchers suggest that you bring your own pillow or sleep in a room similar to your bedroom next time you sleep away from home.
