" Breeds next with the greatest percentage of dogs exhibiting serious aggression (bites or bite attempts) toward humans included Dachshunds, Chihuahuas and Jack Russell Terriers (toward strangers and owners); Australian Cattle Dogs (toward strangers); and American Cocker Spaniels and Beagles (toward owners). More than 20% of Akitas, Jack Russell Terriers and Pit Bull Terriers were reported as displaying serious aggression toward unfamiliar dogs."
Deborah L. Duffya, Yuying Hsub and James A. Serpella, Breed differences in canine aggression. Applied Animal Behaviour Science, 2008 (in press), Accepted 18 April 2008. Available online 3 June 2008.