1. The green and yellow in a cat's eyes are very obvious. When a cat is used to the world being gray, it will be afraid if it suddenly finds something very bright. This is a biological instinct. 
2. A self-protective mechanism evolved in cats, stemming from their deeply ingrained outdoor survival instincts. Therefore, a cat might mistake a cucumber for a snake, triggering its alarm. This fear response is an evolutionary adaptation; by inducing avoidance behavior, the probability of genetic inheritance is increased, thus reinforcing and strengthening these traits.
Meanwhile, to improve the efficiency of the fear response, a fuzzy recognition mechanism often develops: a similar shape and color can be used for identification, similar to the feeling of seeing a snake in a cup. The cost of misjudgment in this mechanism is far less than the benefit of avoiding a real snake, so it is easily retained. Furthermore, research has confirmed that human infants can recognize and avoid images of snakes and wild animals, and have the ability to call for their parents.
3. Cats are a relatively timid species and are sensitive to unfamiliar environments.
