Most breeds of dogs have a special trait that is a characteristic of their breed. For example: huskies love to forge ahead--to pull. Man has used that skill to his advantage. But that particular trait is not desired in an Alzheimer's dog because it is not needed to complete the work task. On the other hand, herding dogs are prized for their skill in herding/retrieving. It is critical that the Alzheimer's dog "retrieve" the caregiver to the location of the patient. In selecting a canine candidate for Alzheimer's training it would be feasible to choose the herding dog over the husky.
You need to know exactly what the Alzheimer's dog has to do to successfully perform its job. Then you will recognize what canine traits are necessary for the dog to learn. Alzheimer's dog will have to listen for its special sound, identify it, verify that the patient is indeed up, alert the caregiver that the patient is on the move, and then retrieve the caregiver to the patient's location......... listening and retrieving skills are top priority. The dog must naturally use its ears more than its nose. You do not need a dog that is always "following its nose for scent", but rather the canine that is sharp and focused upon sounds. Key to Alzheimer's dog is using its ears to hear if the patient is getting up and then retrieving the caregiver to the patient's location.