page 42 bottom of page left para
"by 7 weeks of age puppies are least inhibited and therefore best able to adapt to new experiences" "although continued socialization with other dogs is important, the focus of socialization should now be shifted toward as many new people and situations as possible"
Nothing here suggesting it is ONLY breeders that can do this.
https://books.google.co.uk/books?id=...tudies&f=false