Why do some people "recognize the bed" and can't sleep?

Many people who usually sleep well are not used to sleeping in a "new" bed when they are on business trips, traveling or visiting relatives and friends. They tossed and turned, unable to sleep at night. China people usually call this phenomenon "bed recognition" for a reason. In the field of sleep research, there is another term called bed recognition, which is the first night effect. In other words, our behavior of "recognizing the bed" can be scientifically explained.

? In fact, only half of people can sleep in a strange place. What about the other half? They will produce what we call the "first night effect", and our brains will be "vigilant" to protect their own safety and prevent unexpected potential threats. But now it is a harmonious society. What's the use of this protection mechanism? On the contrary, the other half who "recognize the bed" lacks sleep, which leads to low work efficiency. Actually, don't worry too much. Generally speaking, the protection mechanism of this "first night effect" is only obvious on the first day. After a night of familiarity, even if you know the bed, you can enter the deep sleep stage.

When we sleep, our brain will go through a series of sleep stages, and the time we spend in each stage is different, as shown in the above picture. When we sleep the deepest, it is in the third and fourth stages (the third and fourth stages in the picture). At this stage, our brain will produce very slow and synchronous fluctuations, and our body will recover at this stage, because protein will be synthesized at this stage, and growth hormone will help us recover and grow. In addition, the glucose level in our brain will be replenished at this time, and deep sleep is also very important for us to consolidate our memory. As the picture shows, we spend more time in deep sleep first, and then in shallow REM sleep. In the rapid eye movement stage, we sleep lightly and dream easily.

? A research team recruited a group of students to take a test in the sleep lab. EEG was used to record the brain waves of these students during their two-day sleep. The results show that the slow wave in the left hemisphere of the students' brain is obviously weakened on the first night, and the left brain wave adapts to the right brain wave on the second night, which shows that the students' brain has basically adapted to the new environment. In the second experiment, a new group of students were invited. They are told that their headphones may make a faint beep when they sleep, but they need to ignore this. Most beeps are the same tone, but there are also some differences, slightly different from the same tone. Generally speaking, the left and right hemispheres of the sleeper will respond to these different tones, which are manifested as waveforms of brain waves. But the fluctuation of the left hemisphere is more obvious, which shows that the left hemisphere is more sensitive to non-uniform noise than our right hemisphere. Similar to the previous experiment, the difference between the two hemispheres disappeared the next night.