The socialization/domestication period

By three weeks of age a puppy has learned that it is a dog, by recognising its mother (filial imprinting), developing a social preference for dogs (fraternal imprinting) and establishing a sexual orientation (sexual imprinting). Having identified its own species, it can then learn to interact with other species.

Dehasse says that puppies demonstrate an investigation-attraction behavior towards the unfamiliar as soon as they are able to express this attraction, at around three weeks. This attraction subsides after the fifth week until at least nine weeks. The attraction behavior recedes under the influence of fear-of-the-unknown behavior which grows slowly after five weeks.

Puppies raised in isolation from humans readily approached an observer at three to five weeks. But when contact was delayed until fourteen weeks the puppy actively avoided the observer, and attempts to socialise the puppy were unsuccessful.

The experiments Dehasse describe suggest:

1. Interspecies socialisation (including domestication) is easily acquired in the socialisation period but requires permanent reinforcement to avoid de-socialization. (Puppy needs ongoing friendly contact throughout life to remain socialised.)
2. It is not generalisable to all individuals of the species concerned but remains limited to the individual's characteristics. (Thus a puppy socialised to a young woman and her girlfriends will not be socialised to men with glasses, old ladies with walking sticks or playing children.)

The interactive presence of other species in this period (cats, chickens etc) also leads to interspecies socialisation and attachment and counters predatory behavior. So if you want your puppy to live with other animals, introduce them during this period.