The early socialisation period in puppies and kittens determines lifetime behavioural welfare, making the weeks between 3-12 weeks the most welfare-critical of their lives.
The socialisation window represents the most welfare-critical period of a companion animal's life outside of birth. Experiences — positive and negative — during this period have disproportionate influence on lifetime behavioural welfare because neural plasticity is at its peak and emotional associations are being laid down. Puppies not exposed to a diverse range of people, environments, sounds, and animals during the critical window are significantly more likely to develop fear and anxiety disorders as adults. Kittens require similar exposure to human contact and varied stimuli during their shorter sensitive period. The commercial incentive to release animals early from breeders competes with the welfare need for continued socialisation with littermates; reputable breeders balance both. Puppy and kitten socialisation should be a defined component of welfare standards for breeding and sale.