在撒哈拉大沙漠,有一种沙鼠,一到夏天,就不停地把草根搬回洞穴,即使洞穴里的草根已足够安全过冬,它们依然不停地忙碌,不停地寻找草根,不停地把草根搬回“家”。针对沙鼠的这种本性,动物学家做过这样一个实验:为沙鼠提供足够的草根,然后封锁洞穴,然而洞里的沙鼠却仍然寝食不安, In the Sahara desert, there is a kind of gerbil. When summer arrives, grass roots are constantly being moved back into the cave. Even if the grass roots in the cave are safe enough for the winter, they are still busy and constantly searching for grass roots. Move grassroots back to “home.” In view of this nature of gerbils, zoologists have done such an experiment: provide gerbils with enough grass roots and then block the caves. However, the gerbils in the cave are still uneasy.