Fear of strangers is one of the most common behavioral problems in dogs, often rooted in inadequate socialization and causing chronic anxiety that reduces quality of life.
Dogs that fear strangers experience chronic anxiety in social environments that are unavoidable in modern life. A dog that fears visitors, strangers on walks, or unfamiliar handlers at the vet faces repeated fear experiences that accumulate into a significantly reduced quality of life. The genetic and developmental origins of the problem make prevention through proper socialization far more effective than treatment. The welfare tragedy is that fear often develops during the sensitive period when owners are most confident their puppy will 'grow out of it' - by the time fear is clearly established, treatment is much more difficult.