As mentioned above, socialization to other animals, including dogs, is almost as important as socialization to people. Generally, dogs raised in kennels do not get well socialized to people though some breeders try to offset this lack of exposure by arranging for occasional exposure of pups to a few of their friends. The latter efforts, though well intentioned, are usually inadequate and do not achieve full socialization.
Good socialization is only easily achieved in a home-based setting in which pups are allowed to move around and interact relatively freely. In short, more time in a kennel or crate means less socialization. Dogs in kennels may learn canine etiquette from their mother and littermates but may not be comfortable around unfamiliar dogs if they are not actively socialized. Such dogs will know how to signal their displeasure and ward off unwelcome strangers or submit to forces they perceive are beyond their control. Nevertheless, this is not an acceptable endpoint.*
Attempting to socialize dogs to people and other dogs after the sensitive period of learning (after 12 to 14 weeks of age) is a much less efficient way of proceeding. Being proactive about socialization and investing time when a pup is young is definitely the way to go. Sure it takes time and effort but the payoff is huge. The more time and energy you invest in raising pups the better they fare in the long run, both in terms of confidence and their ability to fit in with society.
Don’t be fooled by unknowledgeable trainers who tell you that taking your dog to a supermarket parking lot to meet thousands of people will achieve socialization, or ones that tell you to take your dog to a Little League game to socialize him to children. Socialization should begin at home when a pup is young and should continue throughout life. It’s always better to head a potential behavioral problem off at the pass than to try and fix it down the road. Early socialization is perhaps the best behavioral epitome of the old adage “prevention is better than cure.”
It has recently been shown that a greater proportion of children who spend more than a certain amount of time in daycare exhibit behavioral problems. Daycare could be construed as the human equivalent of a kennel for puppies. In all probability, it could be demonstrated that the more time a puppy spends in a classical kennel situation, a pen, or crate, the greater the incidence of behavioral problems will be.