Your puppy's mom and littermates played a significant role in teaching her what is acceptable behavior with other canines and what is not. Mom was quick to correct, and littermates yelped and refused to play if a puppy's bites were too hard or her play was getting obnoxious and over the top. Playing with other puppies (and mom) teaches a pup bite inhibition, or how to play-bite without hurting anyone. That is a really important lesson for dogs of all breeds because no matter the size of a dog, a hard bite hurts and can break the skin.
It is also important for your puppy to be introduced to many gentle, kind people while she is still very young. The first critical period for socialization impressions to be made with a pup is over at roughly twelve weeks of age. If your breeder keeps her puppies until they are this age, she will have the initial responsibility for exposing her pups to all kinds of kind visitors.
Problems can occur with puppies that are separated too early from their moms and littermates. These pups apparently have not learned their bite-inhibition lessons, and many professional trainers note that this early separation seems to cause more issues later with training. Many Chi pups are not sold until twelve weeks of age. If you purchased a puppy younger than ten weeks, be aware that you may have some catch-up work to do in the pup's socialization and bite-inhibition work.
If he's a quality breeder, he will have done this. Friends will be invited to see the puppies, as well as potential buyers and older children from the neighborhood, and they will get lots of handling and touching from the breeder himself. If you are purchasing a puppy from a breeder who has not done any socialization with her pups, you will have some catching up to do. But don't despair if the situation is not ideal. Remember, everything you do with your puppy makes an impression, and you can go far in bringing your puppy back up to speed socially.
Socialization with Dogs
The experts all agree on the “how” of socializing your puppy with other dogs; they just don't all agree on the “when.” Some professional trainers feel the risk of raising a frightened or dog/dog aggressive puppy (by not continuing the pup's socialization with other dogs) is greater than the risk of coming in contact with a dread disease.
If you live in an area that has a high risk for lethal puppy diseases, such as canine parvovirus or canine hepatitis, your veterinarian will not want you to take your puppy out for meet-and-greets where dogs and their owners congregate, such as a dog park. You have no way of knowing which dogs have been vaccinated and which have not, nor can you be entirely sure that the park grounds are free of disease. In fact, you can pretty well assume that in these areas, it is highly likely that your Chi will be exposed to a deadly virus or bacterial infection.
What you do want to do is open your home (a safe place) to people who have friendly, unaggressive, vaccinated dogs. Avoid other puppies until they have finished their complete vaccination series.
Socialization with People
Continuing your pup's socialization after she leaves the breeder's home is critical to her future relationships with guests in your home, friendly strangers in the street, or just people in general, of any age, race, size, and shape. If not socialized with people and given lots of opportunities to realize that an extended hand from a nice person means something good is going to happen (such as receiving a small treat), a Chihuahua can become timid of people, defensive, or even a bit aggressive.
Many people who have good intentions can be way too overbearing when greeting a toy-breed puppy. You must be your puppy's advocate. Do not hesitate to tell the greeting person exactly how to meet your puppy — by allowing the puppy to make the first move toward the person's outstretched, treat-laden hand.
With a puppy, you'll see that it's very easy to find people to offer your pup treats. Who wouldn't want to “Ooh” and “Aah” over an adorable little Chi? But you must be very careful that you do not overstep your puppy's level of comfort. One puppy may not initially want a person to come closer than five or maybe even ten feet, while another Chi puppy may feel comfortable trotting right up to a stranger and receiving a light pat.
Gauge your pup's starting safety zone with strangers, and work to improve on this or to continue to maintain a happy, friendly dog. Don't think that because you already own an extroverted Chi that she will remain this friendly. Socialization is an ongoing process that should be continued throughout a Chi's lifetime.