Socialisation is one of the single biggest factors deciding whether a puppy grows into a confident, well-adjusted adult or a nervous one prone to fear-based aggression. It works by building confidence in novel situations while a puppy's brain is naturally primed to form these impressions quickly. The socialisation window is wide open until around twelve weeks of age and gradually narrows until around eighteen weeks. Choosing a breeder who takes early socialisation seriously matters greatly, as puppies raised in family homes with exposure to everyday stimuli get a head start. Create a list of experiences to introduce gradually, always keeping encounters positive. Continue socialisation beyond eighteen weeks at a slower pace for ongoing benefits.