the best thing is socialize and supervise from day one. If a dog has never been near another dog for 8 years they might not like other dogs, ever. But if a dog has been around other dogs and cats and birds and so forth since being a puppy then they will be more accepting. If you adopt a dog that has not been socialized you need to treat it as a puppy, supervise and expose to other animals at a safe distance and reward good behavior