Similarly to infants, in chimpanzees the sense of touch is highly developed. As newborns they see and hear poorly but cling strongly to their mothers. Harry Harlow conducted a controversial study involving rhesus monkeys and observed that monkeys reared with a "terry cloth mother", a wire feeding apparatus wrapped in softer terry cloth which provided a level of tactile stimulation and comfort, were considerably more emotionally stable as adults than those with a mere wire mother. For his experiment, he presented the infants with a clothed surrogate mother and a wire surrogate mother which held a bottle with food. It turns out that the rhesus monkeys spent most of their time with the terry cloth mother, over the wire surrogate with a bottle of food, which indicates that they preferred touch, warmth, and comfort over sustenance.