Three types of trained dogs are generally called assistance dogs: guide, hearing, and service dogs. The most familiar and easily identified are guide dogs trained to help the blind or sight-impaired get about. Guide dogs steer their owners around cars, other people, and all other obstacles, steadfastly ignoring all outside distractions.
Hearing or signal dogs help hearing-impaired people by alerting them with a nudge to important sounds: intruders, phones, crying babies, doorbells, and smoke alarms. Many hearing dogs also ride along in cars to alert their owners to the warnings of ambulance sirens and honking drivers.
Service or support dogs are the arms and legs of many physically disabled people. They pull wheelchairs, carry baskets and briefcases, open doors, and even turn on lights for their owners. Those who suffer from balance problems are often paired with service dogs that help steady them as they negotiate steps and rocky terrain that were formerly off-limits. Seizure-alert dogs warn owners of impending seizures.
Some dogs guide autistic or developmentally disabled people through everyday tasks, and may be trained to give calming, reassuring snuggles to owners who become agitated or withdrawn.
Although the lengthy and intensive training these dogs receive is expensive (most, but not all, dogs are trained in special schools), once the dogs are paired with an owner, they work cheap. One study found that people who had a service dog for a year spent 68% less on hired assistants than they had before. ("The Value of Service Dogs for People With Severe Ambulatory Disabilities," by Karen Allen and Jim Blascovich, Journal of the American Medical Association, April 3, 1996.). That study found significant psychological benefits as well: All the participants (48 people with severe ambulatory disabilities) showed substantial improvements in self-esteem and psychological well-being within six months of getting a service dog.
Dogs also play an important role in the day-to-day social interactions of their owners. Deaf people, for example, suffer the additional stress of having a hidden disability—one they must explain to new acquaintances. A hearing dog is a social ice-breaker, making the process easier for everyone. ("The Socializing Role of Hearing Dogs," by Lynette Hart, R. Lee Zasloff and Anne Marie Benfatto, presented at the national conference of the Animal Behavior Society (July 1996).) And there is considerable evidence that people without physical disabilities are more likely to interact with people who have disabilities when they are accompanied by assistance dogs. (See, for example, "Social acknowledgements for children with disabilities: effects of service dogs," by B. Mader and L.A. Hart, Child Development, 60: 1529-1534 (1989).)
Because of their general temperament and size, Labrador retrievers and golden retrievers are the breeds most often trained as guide or service dogs. More excitable breeds like terriers and poodles (and all kinds of small mixed-breed dogs) often make good hearing dogs; they respond to sounds without waiting for a command from an owner. While some programs differ, most dogs are bred at the training site, then spend their first months with skilled volunteers or families who teach them simple obedience and social skills. The dogs are then returned to the training facility, where they are spayed or neutered and put through intensive schooling. Only about half graduate. Some don't have the calm demeanor required; some just can't resist chasing squirrels or cats.
Potential owners must pass tests, too. They are screened and interviewed to ensure that they are in fairly good health, that they want the dog for mobility and independent living, and that the dog would have a good home and adequate exercise. Owners are then teamed with dogs that have the skills and temperament they require. In most programs, the owners stay on-site for several weeks under the supervision of trainers, who teach them handling and grooming. The owner and dog then go home to live and work together.
A therapy dog is not paired with just one person who has a disability, but provides joy to many. These dogs were first used in institutions such as nursing homes and schools for emotionally disturbed children. Volunteers now take them to hospitals, schools, hospices, and nursing homes, where they cheer residents. Unlike individually trained assistance dogs, they do not accompany owners to public places.
It's easy to see the necessity of assistance dogs that are pulling wheelchairs or guiding owners with visual impairments. But what if the dog's function isn't obvious? For example, you can't tell just by looking that an ordinary-looking dog is actually a seizure-alert animal that could save his owner's life.
Generally, all an owner needs to do to get a service dog admitted to public places, rental housing, or a workplace is explain what the dog's is trained to do. The owner does not have to produce evidence of special training or spell out personal, private details of why the dog is necessary.
All that makes sense. Problems have arisen, however, when owners want their dogs with them not because the dogs have special training to "do" something but because they feel the dogs' mere presence is essential. These "emotional support animals" may or not come with doctors' letters that say the animals are necessary for owners who suffer from anxiety, depression, or phobias. Psychologists do not dispute that dogs can often improve their owners' emotional well-being, but the Americans With Disabilities Act does not classify these dogs as service animals.) They may, however, be allowed as reasonable accommodations in rental housing and when traveling.