Domestic cats, especially young kittens, are known for their love of play. This behavior mimics hunting and is important in helping kittens learn to stalk, capture, and kill prey. Cats will also engage in play fighting, with each other and with humans. This behavior may be a way for cats to practice the skills needed for real combat, and might also reduce any fear they associate with launching attacks on other animals.
Owing to the close similarity between play and hunting, cats prefer to play with objects that resemble prey, such as small furry toys that move rapidly, but rapidly lose interest (they become habituated) in a toy they have played with before. Cats also tend to play with toys more when they are hungry. String is often used as a toy, but if it is eaten it can become caught at the base of the cat's tongue and then move into the intestines, a medical emergency which can cause serious illness, even death. Owing to the risks posed by cats eating string, it is sometimes replaced with a laser pointer's dot, which cats may chase. While concerns have been raised about the safety of these lasers, John Marshall, an ophthalmologist at St Thomas' Hospital, has stated that it would be "virtually impossible" to blind a cat with a laser pointer.