A dog’s aggression towards people is the one most important issues concerning behavior.  Biting is the highest level of aggression and previous studies of aggression in dogs have been largely based upon actual dog bites.  But what about the broader variety of aggressive behaviors including those of lower intensity?
A study involving 3897 dog owners from the United Kingdom focused on estimating the number of dogs showing aggression towards people in three different situations.  The first being aggression towards unfamiliar people entering the home, the second was aggression towards meeting unfamiliar people outside of the home, and lastly, aggression towards family members.  The dog owners in the study were asked if their dogs ever barked, lunged, growled, or attempted to bite a person and, if so, was this behavior a continuing problem.
The study found the rates of aggression to be quite low.  Over the lifetime of the dog, 3% of owners reported aggression towards family members, 7% reported aggression towards unfamiliar people entering the house, and 5% reported aggression towards unfamiliar people outside of the home.  This is a remarkably low frequency rate considering whether owners reported any aggressive behaviors at all – ever.
The researchers also addressed the question of whether some dog breeds are more aggressive than others by comparing the rates of aggression of dogs of specific breeds with a random sample of mixed breeds.  Breeds showing significantly less aggression towards unfamiliar people entering their house include Labrador and Golden Retrievers, Cocker and Springer Spaniels as well as other retrievers.  Setters are low in aggression and terriers were significantly lower in aggression towards people than the mixed breed reference group.  Although other research shows Pit Bull – Type Terriers to be higher in aggression, this was not confirmed in this particular research.  Also, Boxers showed low aggression towards visiting strangers.  In this study, only German and Belgian Shepherds reported increased aggression towards unfamiliar people outside of the house when compared to the cross-breed group.
One cannot over-emphasize the positive effects of puppy socialization classes.  A puppy attending classes on at least two occasions before the age of 12 weeks reduced risk of aggression towards unfamiliar people entering the house by 1.4 times and a 1.6 times reduced risk of aggression towards unfamiliar people outside of the house.  While on the subject of training, the type of training a dog receives effects his risk of aggression.  Training procedures based on punishment increases the risk of aggression in dogs as they are associated with a 2.9 times increased risk of aggression to family members and a 2.2 times increased risk of aggression to unfamiliar people outside of the house.
Although the study was complex, it makes it clear that breed, puppy socialization, and training methods have significant effects on the risk of dogs showing aggression towards people.