The Socialization Window
The timeline for puppy social development is fairly short. By eighteen weeks of age, your puppy should have met all kinds of different people — men, women, children, people of different races, people dressed in uniform, people wearing hats. The more varied your Golden Retriever puppy's social experience, the more friendly and social he will be, and the less risk of aggression or other serious behavioral problems you will face.
Dog-to-dog socialization is ongoing as well. You want your Golden Retriever to be socially normal around dogs, meaning he is able to interact and play with them without becoming frightened or aggressive. To reach this goal, he must play with all different types of dogs on a regular basis. The dogs in the neighborhood are a good start, but your puppy must meet and play with as many different types of dogs and puppies as possible. Your Golden depends on you to help him develop the social skills he needs to get along with other dogs.
Golden Retriever puppies are not couch potatoes. Energy levels vary from one pup to the next, but most Golden puppies are highly energetic long before they actually mature into calm, well-mannered adults. But left to their own devices, your Golden will never grow out of his bad habits. He will become more and more of a nuisance if not given the right guidance. Start your Golden's socialization and training now — he's getting bigger every day.
It's a good idea to enroll your Golden puppy in a puppy kindergarten class at about twelve weeks. At this point, he and the other puppies in the class will have had at least their first round of vaccinations. They should all be able to enjoy each other's company safely.
The crucial point to understand about puppy social development is that you have a very limited time to get things started. You cannot wait until your puppy has been fully vaccinated to socialize him to other dogs.
After the eighteen-week mark, the window for socialization starts to close. If you haven't started socializing your Golden to other dogs and various types of people, he will develop behavior problems (usually aggressive in nature) that will be a permanent part of his personality. It is so much easier to start out right from the beginning than try to fix it later.