Autonomous movement is one of the main forms of motion-like perception. On a moonless night, when we look up at the sky, we sometimes find a small and shiny thing swimming in the sky. We will mistakenly think that it is an airplane, but it is actually an autonomous movement caused by a star. In a dark room, if you light incense or cigarette butts and look at this light spot, you will also see that this light spot seems to be moving.

Parasite refers to a creature that lives in another animal called host for most of its life, and at the same time causes damage to the parasitized animal.