Dogs in general, under free-ranging conditions, will live in mixed-sex, mixed-age social groups. Social ranking is determined by age, although sex may play a role. Females seem to be responsible for leading more often than males. Social ranking is maintained primarily by deference, not by agonistic interaction. Sexual maturity in domestic dogs (including the shih tzu) occurs between 6 to 9 months of age (later for giant breeds), while social maturity begins to develop at 18 to 36 months of age.

At social maturity, a hierarchy depends upon age, sex, size and temperament. In a free-ranging group, dogs that challenge the established social hierarchy may leave and form their own groups if they do not succeed in altering the extant social order. Social maturity is also the time when problems such as aggressions and anxieties develop. Roaming, mounting, urine marking, and intrasexual fighting are caused by the sex hormones, particularly testosterone. These problems can often be prevented or greatly reduced by neutering, especially in males, in households with several pets, males and females, or a household with all males.

Between 3 and 8 weeks of age, dogs tend to focus on other dogs (if available) for their social stimuli. Between 5 and 12 weeks of age they seem to start to focus more on people if people are available. Dogs are most receptive to learning about how to deal with new or different environments until about 16 to 20 weeks of age. This is not to say an older dog would never adjust to a change in environment. It is just to say the adjustment is easier before this age. With time and patience any dog of any age will adjust to change just as people do.

It is not critical to switch the focus of exposure either to other animals or to people at any one specific period. Given the adequate opportunity, puppies will learn about the social and physical environments when they are ready. Trying to introduce them to a specific situation is not critical to producing a well-socialized puppy or adult dog. Of great importance is to avoid extremely fearful stimuli.

Dogs kept exclusively in cages and kenneled and not exposed to people at all after 14 weeks of age may have severely undeveloped social skills. If you are purchasing an older dog from a private breeder, this problem is not likely to surface. The type of older dog I am talking about here would be one that was raised exclusively in kennels with cage after cage and perhaps 3 or 4 or maybe more dogs sharing the same cage. Maybe their only contact with people would be the short presence of someone passing by with water or food. Usually dogs that are raised by individuals in private circumstances have adequate and quality contact with people.

Regardless of the age of a puppy or dog, that life needs to be shown a daily caring atmosphere from their human caretakers to be able to provide them with the ability to adjust readily and easily in new homes or environments. Without human interaction and caring, the dog may experience social problems and behavior problems that otherwise would have not surfaced.