my thoughts on yapping is that you cant cause a dog to do it by foolish handling like slipping on stuff it has no chance of catching or running it too young or unfit, these things will all show the fault up if the dogs that way inclined but if a dog doesnt have the trait it will never utter a peep no matter how much stick you give it at what age. you could rear 2 pups exactly the same way same feeding exercise training and give one some runs at 10 month old and it wont make a sound its whole life and hold the other one off til its 14 month and it could yap for no reason. some dogs do it as pup