Thanks to dogged for finding this site!
http://www.diamondsintheruff.com/Develo ... tages.html
DEVELOPMENTAL STAGES & SOCIALIZATION
What happens when - how your puppy changes and develops
"Puppies provided with poor socialization or deprived of environmental exposure often develop lifelong deficits and dysfunctional behaviors. A puppy isolated early in life from other puppies and humans will not only fail to establish satisfying social contact with conspecifics or enjoy companionship with people later in life (such puppies are extremely fearful of any social contact), they will also exhibit widespread behavioral and cognitive disabilities as well. Isolated puppies exhibit poor learning and problem-solving abilities and are extremely hyperactive or rigidly inhibited, are emotionally over-reactive and unable to encounter novel social or environmental situations without extreme fear and avoidance, and are socially and sexually incapacitated." - Handbook of Applied Behavior and Training, Steven R. Lindsay
Please see website for chart breaking down the ages and stages of puppy development.