While the social aspects of behavior in the puppy have been noted, it is equally important to see how alterations of the normal socialization process can modify subsequent adult behavior. The term critical period becomes meaningful here since this is a time in the puppy’s life when many or all aspects of its behavior are particularly susceptible to modification. Simply stated, it is the time when the early experiences of the puppy will have the greatest effect on the subsequent behavior of the adult dog.
Puppies socializing between six and eight weeks respond to human beings much better as adults than puppies allowed to socialize before or after that time. Puppies that did not receive any socialization with man during the critical period were essentially unapproachable and untrainable as young dogs and adults.
Hand-reared puppies have been socially isolated from their littermates. These puppies show great deficits in social behavior and in reactions to their own species. These puppies are non-vocal, non-oral, non-aggressive and passive with other puppies. They rapidly become aggressive towards their peers following socialization and rarely engage in group play. They tend to wander off alone and engage in self-play or to manipulate inanimate objects. Some of the hand-reared pups become aggressive enough to achieve dominance over their peers. Although hand-reared puppies are socially attracted to humans, they do not show the affection towards humans that is normally seen.
Early socialization is extremely important in dogs destined for specific jobs. Investigators studied the effects of delayed socialization on the trainability of guide dogs. All puppies received a limited amount of socialization to humans for the first twelve weeks of their lives. 
Following this time, the puppies were placed in private homes at varied times. Some puppies were placed immediately at twelve weeks of age, others were isolated for one, two, or three weeks respectively before being placed in the private homes. Of those puppies that were placed in private homes at twelve weeks of age, 90% became guide dogs. However, when similar puppies were isolated for two weeks following the initial twelve weeks of socialization, only 57% were successfully trained as guide dogs. Furthermore, if puppies were isolated for three or more weeks, only 30% were successfully trained. Therefore, social deprivation after the critical period of socialization may result in the young dog’s becoming asocial. This often occurs in large breeding kennels where it is a common practice to let dogs mature before training is begun. The majority of these dogs may make decent hunting dogs, but they tend to hunt for themselves and pay little attention to the handler. Some dogs that are reared in this manner develop a syndrome referred to as “kennelosis.” They exhibit timidity and will run from strangers. They may in fact show fear responses when someone tries to catch them.
There is a critical period of socialization for young puppies, and to deny a puppy this experience will have lasting effects which may severely alter the normal adult behavior of a dog and render it incapable of forming appropriate social bonds either to humans or to other dogs. It is to be hoped that more dog breeders will become aware of the critical period of socialization and will raise litters of puppies in such a manner that proper socialization occurs. If this is performed conscientiously, it will undoubtedly reduce the incidence of maladjusted dogs and dissatisfied pet owners in today’s society.
Our recommendations are:
- Puppies should stay with their litter until they are eight weeks of age.
- Litters should have human interaction from week three on.
- Puppies should be placed in a human home environment shortly after leaving the litter to prevent “kennelosis”.
- Hand raised puppies or puppies removed from their litter before 8 weeks of age should interact with other puppies in some way (puppy day care) so they can better socialize to dogs and people.
SOCIAL RELATIONSHIPS OF KITTENS
In contrast to the dog, the cat is a much less gregarious species. Cats do not exhibit the high degree of sociability and dependency seen in dogs. Because of this independent attitude, some people refer to the cat as asocial, which is erroneous. The social organization of any species is usually very complex. This is particularly true of the cat. Consequently, the social relationships of the cat are often misunderstood and oversimplified.
The early experiences of the young kitten are also important in determining the developing and subsequent behavior of the adult cat. The early behavioral development of the kitten will be discussed as it relates to the socialization process in kittens.
Compared with puppies, kittens develop more rapidly. Their eyes and ears are functional at an earlier age, allowing them to observe the environment and respond at a younger age than the puppy. The kitten brain is nearly mature by five weeks of age. Although the sensory capacities of the adult are present at an earlier age, the motor skills necessary for the refined movements of tree climbing, prey catching, and running take longer to develop. In addition, the young kitten lacks the experience needed to survive. One way in which this experience is provided and enhanced is through interactions with the queen. The period of time that the queen devotes to her kittens, is prolonged compared to that of a bitch and her puppies. Consequently, there is more opportunity for the kittens to observe and perhaps learn from the mother. The development of behavior in kittens depends on a continual and progressive interchange between mother and kittens beginning at or before birth. In addition, many of the behavior patterns that develop in the kitten focus around the feeding process.
Immediately after birth, the queen licks the kittens vigorously. This stimulates respiration in the kittens and perhaps intensifies the social bond between them. Nursing usually begins within the first hour after birth. There are three stages of mother-infant interaction in nursing. The queen initiates the nursing activity; this stage lasts for the first two to three weeks of the kitten’s life. Nursing is initiated by the female’s enclosing response. The queen approaches one or more of the kittens, lies on her side, draws her front legs back and her back legs forward thus enclosing the kittens. The kittens are guided to the nipples by their response to the shape of the mother’s body presumably by tactile perception (touch), but at first they gain them only after much nuzzling and fumbling. Since the sense of smell is well developed in kittens, it is possible that olfactory (smell) cues also guide the neonatal kitten to the mammary glands. In addition, thermal cues are no doubt utilized. From the first day onward, their suckling behavior is influenced by experience. Individual methods of suckling involving teat preference may develop. Some kittens may suckle from the thoracic pair alternating from side to side while others may prefer the inguinal nipples. Still other kittens may not show any preference and will suckle wherever there is a free teat. This development of teat preference may reduce competition and perhaps provides optimal stimulation for continued and productive lactation.
Between 20 and 30 days of age, the nursing can be initiated by either the mother or kittens, but usually the latter. By this time, the eyes and ears of the kitten are functioning well, permitting them to leave the nest and begin to interact with the queen outside the nest. The queen usually cooperates by immediately lying down or by making the teat available if she already is lying down. After 30 days, there is a third stage to the nursing-sucking relationship. This stage extends to the time of weaning and is thus variable in duration. During this stage, practically all of the nursing is initiated by the kittens. The kittens follow the queen with increasing frequency, and as the time progresses, the queen frequently avoids nursing attempts of the young. This may be accomplished by simply being away from the young or batting at them with her paws.
During the early days of birth, the social relationships between mother and kittens are strongly influenced by the latter’s attachment and orientation to the “home corner.” This is an area of the nest that has been saturated by the placental fluids at the time of birth. 
As early as a few hours after birth, odors from this site, as well as contact with the queen, have a quieting effect on the neonatal kitten. Initially, the kitten orients to this corner by using its senses of touch and smell. If a kitten is placed outside the home corner, it crawls around until it orients itself (smells the nest) and then crawls to the home region. It is thought that the ability of kittens to orient to the nest plays a role in keeping the litter together and prevents them from straying from the nest.
Coinciding with the time the kittens begin leaving the nest area is the emergence of play behavior. Initially kittens paw or bite at one another. Shortly thereafter, they begin to chase, stalk, roll over and wrestle with one another. Many of the actions seen such as, fighting, chasing, and prey catching are a part of the social play exhibited by kittens. The behaviors a kitten exhibits when playing with a ball or toy are basically prey catching actions. Kittens frequently can be observed jumping in the air trying to catch some invisible object or chasing along the floors or ground trying to catch an imaginary object. These activities are referred to as hallucinatory play. This play serves to acquaint young kittens with the environment. Play with other kittens leads to social attachments and development of social relationships. In addition, social play may strengthen relationships between adults and reinforce the interaction between the queen and the kittens. Play activity is an extremely important part of the behavioral development of a kitten. A kitten deprived of play activity will usually demonstrate some behavioral problems later in life. In particular, it tends to be easily upset and does not seem to learn as readily as does the kitten that has had ample opportunity for social play when it was young. This fact suggests that encouraging this play behavior can develop a stronger cat human bond.
In addition to forming social attachments to peers, most kittens also form some type of social attachment to human beings. Although it is not as clearly defined, there would appear to be a sensitive period of socialization to humans in kittens as there is in puppies. This period extends from four to eight weeks of age.
Frequent handling and playing can aid the process of socializing kittens to humans. Petting the young kitten has been shown to make it more responsive to its owner when grown. Simply picking up the kitten and stroking it appears to have a calming effect and accustoms the kitten to restraint. In socializing kittens to humans, it is important to expose them to many people. This seems to lessen their fear of strangers as adults. Studies show that kittens exposed to many humans during the ages of five to nine weeks were less fearful of strangers as adults than kittens raised with just a one-person contact during the five-to-nine-week period of infancy. It is also during this sensitive period of socialization that the kitten should be introduced to children. A young kitten that is not socialized with children may reject them or even bite them when or after it has reached maturity. Thus, if the kitten is to become a well-adjusted pet, it is essential that it be socialized to humans at an early age.
Socialization of kittens prior to the appropriate socialization period can have undesirable effects, e.g., if a kitten is taken from a litter too soon, it will not experience the necessary social interactions with other cats. As a result it may tend to become too human-oriented. Such cats are frequently aggressive towards other cats and in many cases fail to mate successfully. A queen reared in this manner that does mate and conceive often times will not display the appropriate maternal care-giving behavior and in some cases may kill the kitten. Similar types of behavior are observed in hand-reared orphan kittens. A person who is successful in raising an orphaned kitten is usually extremely attached to him. Unfortunately, these kittens do not make satisfactory pets. As adults, these cats may turn vicious, cannot relate to other cats, appear less healthy, may refuse to mate, and in general are not desirable pets.
Placing a kitten in a new home at the proper age is extremely important. The best age for placing a kitten with a family would appear to be somewhere between eight and twelve weeks of age. Kittens obtained after twelve weeks of age and socialized only to other cats are very difficult to handle and usually do not adapt well to the human environment. Most farm youths know that if young kittens are not found and handled by the family before the kittens are weaned, they usually become wild and will avoid humans whenever possible. In fact, if such animals are caught, they are extremely dangerous and should be handled with great care. As with puppies, a young cat will explore the surroundings in his new home. He must be shown what he can and cannot do. He must be trained and disciplined if he is to become a welcome and well-adjusted part of the family. Contrary to popular belief, cats can be trained if they have been properly socialized and have experienced a normal infancy.
