Socializing is one of the most important things a breeder and new owner can do with a puppy. The socializing should start right from day one and continue through to a dog's adult life.
Social: to make social; make fit for life in companionship with others.
Dogs left in a pack, away from human contact and regular daily life are far from the social dogs we thrive to live with. Many dogs come from sketchy pasts to say the least and these dogs can have a great deal of difficulty simply fitting in. It all starts with the breeder; it makes no difference what breed or mix you are talking about, they all need early socializing.
Many breeders now are introducing some form of early stimulation; an introduction to different things very early on. It is not suffice to leave a pile of puppies in a box without different sounds, sites and environments. I've seen a lot of puppies and I've seen a lot of litters; puppies who are given the opportunity to thrive through early socialization are far better equipped to deal with life in general. Early stimulation can be the simple act of introducing new things to a whelping box.
Once puppies are of age to get out of their whelping box they should at least for a part of each day. Of course all dogs being different; some will soar with early stimulation and socialization while some may need some extra work. Puppies who are a bit apprehensive need a great deal of socializing but in well thought out rations. Over stimulating puppies who are shy or fearful can backfire.
Early Neurological stimulation
My new puppy deals with everything in stride; she has a very solid temperament as far as dealing with new things. She notices new things, checks them out and then moves on. Very much like Tilley she deals with new objects easily; unlike Luke who is a nervous type. No doubt Elsa's wonderful life at her breeders which was filled with many new introductions to life itself helped her to become as prepared to deal with life in general.
Even rescue puppies need to be socialized in a big way. Foster parents need to understand the early stimulation and socializing requirements needed to produce well adjusted dogs of the future. Just taking care of their food and a roof over their head is not enough to succeed in life. A puppy needs a great deal of introductions to sights, sounds and texture. Everything that will be in their life around the corner.