Proper socialisation during the critical period from 3-16 weeks has lifelong welfare implications, as dogs that miss this window are at significantly higher risk of fear-based behaviour problems throughout life.
Dogs that miss the critical socialisation window live with heightened fear responses to everyday experiences including strangers, traffic, and novel environments. This is not a behavioural choice but a neurological consequence of developmental timing. The chronic anxiety of an undersocialised dog represents significant lifelong welfare harm that is entirely preventable through responsible breeding and early puppy experience.