Encontrei um artigo que penso estar bastante elucidativo quanto à questão dos 6 meses.
(artigo retirado de http//
www.canismajor.com/dog/puppylrn.html )
Q We’ve been told that we shouldn’t start training our puppy until she’s six months old. Is this true?
A Not at all! In fact, at the tender age of eight weeks, your puppy already has the same learning capacity as an adult dog. Obedience classes usually require their canine students to be six months old because of medical reasons -- to protect the participants, dogs in class need to have their permanent vaccinations, some of which can’t be given until age six months. But this doesn’t mean your puppy can’t start her training before then. With some breeds of dogs, waiting until they’re six months of age could mean you’ll have a serious behavior problem before class even starts.
You can start teaching your puppy simple commands like Sit, Stay and Come right now. Keep your training periods short and fun. Puppies have very short attention spans -- there’s so many things happening that are new and fascinating that it’s impossible for them to concentrate for very long. Use lots of praise and treats. Work on one command at a time and end the session when she’s successfully completed a command. You’ll be surprised just how quickly she can learn!
Some kennel clubs, animal shelters and veterinarians offer “puppy kindergarten” classes for puppies under six months of age. These are great for early socialization with strangers and other dogs, as well as building a foundation for early obedience training. They’re designed to help you and your puppy start your relationship off on the right foot. And they’re a lot of fun for puppies and people alike!