题目内容：

阅读下面短文，在空白处填入 1 个适当的单词或括号内单词的正确形式。

Why do many of us find 1. difficult or impossible to fall asleep in a bed other than our own? Is it because the bed is 2.(comfort)? According to a new study published in Current Biology, a significant reason is 3. 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 4.(stay) awake on the first night in a new environment.

For the study, 35 young volunteers 5.(ask) 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 brains were 6.(active) than the right brains and people had a hard time sleeping. However, left-brain activity decreased as days went by, 7.(fall) even to the point of complete calm. In this process, the participants got an increasingly better sleep experience.

The 8.(finding) suggest that the different rhythms of the sides of the brain affect our sleep. When the two sides work 9.(different), the balance between them is broken. Thus, the brain can’t relax and is sensitive to anything strange in the surroundings, just 10. it is in the daytime.