Puppies still have short attention spans at this age but start to learn right behaviors for the right time, have big improvements in motor skills, pay more attention totheir humans and are very busy learning about their new world. If left with their littermates at this age, they will bond with them instead of their owner. Depending on what the owner expects from the puppy, behavior can be shaped very differently during this time. If kept almost totally seperated from other dogs, the human bond becomes very strong but there is a risk of the dog not acquiring good doggie social skills. If primarily kept with its littermates or other dogs in the household, the puppy will learn better doggie social skills but may have less interest in spending time with its humans. A careful compromise is probably the best answer for most puppies. Research Konrad Lorenz and others show that attempts to change social behavior learned during this critical period are rarely successful. Puppies left with littermates through this time often have problems with excessive barking, seperation anxiety and/or hyper excitability. And conversely, dogs without proper dog-dog relationship (including plenty of play fighting) loose their ability to play with unfamiliar dogs and ecome serious about defending them selves by the age of 11-17 wekes.