Stranger Danger
Aggression or reactivity toward new people is one of the most common and misunderstood behavior problems. Aggression is often a response to fear but can also be a defensive behavior and not fear-related at all.
CAUSES OF AGGRESSION
Fear due to lack of early socialization
Genetics
Learned behavior from mom
Traumatic experience
The most common cause of aggression and fear around new people is lack of socialization during the first 12 weeks of life. Dogs have a small window of socialization, and if this is missed, there are often aggression/fear issues later on. The golden rule of socialization is that puppies should meet 100 new people by 12 weeks of age. This is even more true for defensive, less social breeds. Most puppies meet only a handful of people before 12 weeks..
“BUT MY DOG IS ONLY AGGRESSIVE TOWARD CERTAIN PEOPLE!”
This is very common, and there are lots of reasons your dog may be more aggressive toward certain people than others. People have varying energy levels, physical sizes, volume, body language, and interest in the dog. A calm, small person ignoring your dog will likely trigger less of a response than a large, loud person who immediately tries to pet your dog or children who move quickly and are loud and unpredictable.
Most commonly, dogs have increased aggression toward men and children.
DEFENSIVENESS
Some breeds are more genetically prone to being defensive toward new people, such as cattle dogs, Akitas, German shepherds, Great Danes, mastiffs, rottweilers, etc. For these breeds it is even more imperative to heavily socialize between 3 and 12 weeks to help override their genetic predisposition. These defensive dogs are not afraid but rather view it as their job to keep strangers away, which they will very happily do.
NOT PROTECTIVE
Many owners mistakenly believe their dog’s stranger-aggression is due to protectiveness - wanting to keep the owner safe. The vast majority of the time this isn’t true, it’s just wishful thinking. It’s easier to believe that your growly dog is just “protecting” you from every single person in the world instead of admitting your dog is aggressive and defensive or insecure. Dogs who are actually trained for protection work do not growl and lunge at every person they encounter. They are generally calm and composed until given the command - they have to be TAUGHT to protect.
THE BEST TREATMENT
The best treatment depends on the cause. If your dog is aggressive or reactive out of fear, it’s important to build confidence and begin a socialization protocol. For dogs who are not fearful, a different approach would be more effective. I always recommend working with a trainer when dealing with an aggression issue. Dogs need to be taught that aggressive behavior won’t be tolerated and also taught how to exist and cope with new people.