i really wasn't clear on the aggression thing , imo aggression is aggression , where it's directed doesn't make it not aggression , the motivation behind it may be different , resource aggression can be directed at people as well as littermates , defensive aggression can be directed at both littermates and people , prey aggression , most dogs can differentiate between animals and people , but not all all the time ........... i know firsthand as well as anyone dogs that are animal aggressive are not neccessarily people aggressive , most all dogs learn to differentiate between animals and people ............i've had pups that would try to seriously hurt their littermates , some to the point i'd think they were trying to kill them , they'd bite you when you touched them to stop them , when you held them back they'd continue to try and seriously bite you ..... i 've had pups that would fight their littermates over food , and they'd bite you for trying to take their food also ...... i've had plenty of pups that would try to bite you for doing something they didn't like , like you said "what else can they do" , some pups just take longer for them to learn not to treat folks like their littermates , especially pups that don't get a lot of one on one from the breeder ........ i had a neo pup a vet told me was a problem because i had to hold her head at 8-9weeks , because she tried to bite him when he tried to put her on her side , she lived 12yrs with my babies/little kids , and was about as sweet as dogs get , he actually told me exactly what the op was told by his vet , i never went to that vet again , I was a kid and knew better than that ......... i think what the op described is normal puppy behavior and means nothing as to the dogs future ...... i also believe the best time for correction is as a puppy , it takes very little , pups are easy to correct , and you get a good assessment of how hard or soft the dog is , which is a good guide in how to handle it for the rest of it's life ...... the dogs I found to be the most dangerous to strangers were the soft pups , who usually grow up to be more distrustful ........ the only thing my pups or dogs ever get rolled over for is a belly rub , and they get lots of free stuff ............