While scientists have long studied the role of testosterone and serotonin in aggressive behavior of dogs and other animals, new experiments examine the role of two other hormones – oxytocin and vasopressin. Dogs with a history of aggression toward other dogs had higher levels of vasopressin, while assistance dogs selected for a good temperament were shown to have higher levels of oxytocin.
Read more about the studies of vasopressin and oxytocin in dog aggression in Science Daily. The original research is reported in Frontiers in Psychology.
More on aggression in dogs can be found in the Merck Veterinary Manual.