The ability to quiet animals and make them less sensitive to sights and sounds has been found in many different kinds of animals, including insects, reptiles, birds, and mammals. The effect may have survival value, because many instances of this are found in the wild. For example, baby animals, including kittens, become limp when their mothers pick them up by the neck in their jaws. This is called the “scruff response.” The kitten’s tail curls up between the legs, the back rounds as the kitten pulls its legs in close to its body and becomes passive.
Veterinarians and other pet professionals sometimes use this response to their advantage when they grasp the skin on the back of a cat’s neck (an area called the “scruff”) with their hands, producing the same response seen when mother cats grasp kittens.