I think that the point that people miss when talking about service dogs that are assisting people with impaired perception, whether it is bad data (blind, deaf) or bad processing (Autism, CAPD, dissociation, seizures, migraines) is that the dog is providing *information* and *assistance* rather than *control*. A small child cannot use that information effectively, whether he or she is disabled or not. Small children need to stay by Mommy or Daddy until they are old enough to be able to use information about their environments.
Adults with information-processing disabilities who use service dogs know that a car that is moving towards them can hit them, and that getting hit will hurt them. However, they may not always be aware that the car is there, or be able to connect the fact that the car is there, and is moving, with the other things that they know about moving cars. In a properly-functioning human-dog team, the human is conditioned to respond to the information the dog provides by blocking and guiding, and the dog is conditioned to respond to traffic by blocking and guiding the handler away from it until the handler releases the dog from this behavior. With a small child, there is no teamwork. There is no training or conditioning of the child to respond to information, because the dog is not really providing any information to the child. There is just a dog that thinks that it is in charge of the child and no way for the child to assert his or her own mind and safety.
~ E. R. C.