Cats like string primarily because it triggers their natural hunting instincts. The movement and appearance of a string mimic the movement of prey or a snake, stimulating their predatory drive. Cats also enjoy playing with string because it provides both physical and mental stimulation, keeps them entertained, and has a pleasing texture for them to claw and chew. Additionally, the act of chasing a string can be fun and satisfying for a cat because it simulates the thrill of hunting and catching prey. The similarity of string movement to the movement of a cat's own tail may also play a role in their attraction to it.