Adequate socialisation during the critical early weeks of a dog's life determines long-term welfare through its effects on fear, anxiety, and the ability to cope with normal life experiences.
Socialisation is the single most important factor determining the long-term behavioural welfare of companion dogs. Dogs who miss adequate positive exposure to the range of people, animals, and environments they will encounter in adult life develop fear responses that cause chronic welfare deterioration. The consequences of poor socialisation — fear-based aggression, separation anxiety, noise phobia — are among the most common welfare problems in companion dogs and frequently end in relinquishment or euthanasia. Responsible breeding begins with socialisation in the breeding environment before puppies leave for new homes.