The dog has contributed to the study of behavior . Not only have the interactions among young puppies been studied, but also their interactions with other animals and people. Much of the knowledge gained from these studies is now applied in the training of guard dogs, as well as guide dogs for the blind and hearing dogs for the deaf. Because dogs have a high incidence of kidney disease , they are a natural choice for this research. The first successful kidney transplant was performed in dogs in the late 1950's.
Dogs currently aid research to prevent the rejection of transplanted organs.
Dogs have also made contributions to the study of aging . Like humans, aging dogs have skin that sags, eyes that lose vision and hair that turns gray. Advances regarding aging have thus benefited dogs, making it possible for them to have long lives, many living well past the age of 15 years. Artificial hips and joints for the handicapped, injured and aged were designed and tested in dogs. The most common treatment for human cataracts , the intraocular lens, was developed in dogs.