The socialisation window in puppies closes by approximately 14 weeks of age; experiences during this period fundamentally shape adult behaviour and welfare across a lifetime.
The socialisation window is one of the most important concepts in companion animal welfare because its effects are lifelong. A puppy inadequately exposed to people, other animals, environments, and stimuli during the sensitive period develops fear responses that persist into adulthood regardless of subsequent experience. The welfare cost is borne by the adult dog for its entire life. Early socialisation is one of the highest-impact individual welfare investments a new dog owner can make.