Just watch for the behavior. Mine have grown out of it except for Bandit. And its his attitude and nothing else. He does not like to be held for too long and he does not like to go in his kennel at night and he will twist and bite and scream like nobodys business. He was very very small and when he was born he was not breathing. We worked on him and the vet said hes probably a little slow. But he knows he can throw a fit.