Social mammals are very sensitive to fear signals of the same species. It is a necessary for survival thing, because it makes others in the group aware of potential danger and allows time to flee or fight.
Imagine how it would affect you if you’d hear someone’s scream. It right away raises the level of tension and alertness, hormonal changes take place, the heart is racing and fear sets in. You’d likely be more receptive to the scream than the calm energy of a companion you might be walking with. And that is intensified if you don't have any information what is happening; why the person screams.
Dogs are no exception. Many hear fear and stress signals of their own kind all the time – in a shelter, from neighborhood dogs, in a multi dog household or from punished dogs in a punitive training facility. In addition to being sensitive to same species' fear signals, dogs, because their lives are so intertwined with humans’ since thousands of years, are also receptive to our tensions, fears and stresses.
A dog might not be fearful genetically, but when surrounded and exposed to dogs and people that are, becomes stressed as well and, at that point, is less likely to pick up safety signals that are given by more grounded members. One has to have a very strong sense of safety and confidence to overcome that.
Studies showed that problem children do best when integrated into a group with socially apt and non-aggressive children. Not only do they learn from them, but they are also forced to change their own behavior in order to be accepted and fit in, and social acceptance is a profound need for all social animals. There is no reason to believe that this would be any different with dogs. Of course, and understandably so, neither parents of good kids, nor owners of non-aggressive dogs want the “bad” ones in their midst, and that makes integration and behavior modification more difficult.
What one can do is to expose the problem dog where relaxed dogs are, but in a distance far enough that allows him to observe without getting stressed. That instills safety and trust and then the distance can be decreased bit by bit.
What happens in reality though is often the opposite. The owner signs the dog up for a growl class where all dogs have issues and most humans are tense also, or brings him to the dog park hoping that “socializing”, or maybe even an older and meaner dog teaching him a lesson, will do the job. That leads to even more arousal, aggression, distrust, fear, stress, resistance and suspicion.
If dogs are too reactive to handle a normal class, they should also not be in any other group class or group setting. If we muzzle the dog, he is only physically safe for others, not emotionally safe within himself.
Most reactive behaviors are rooted in fear and distrust in human leadership. With second-hand dogs that could be based on life experience, and not necessarily on mistakes the present owner makes. When we drag such a dog to the dog park, into a class or aggressive seminar, with an aggressive, corrective and intimidating instructor or other reactive dogs, we hand our dog over and send following messages:
I don’t hear your fears. I don’t care that you are stressed. I can force you to do things you don’t want or can't do. I can force you to look at me and I expect you trust me even though I just completely disregarded your fear and forced you.
If you are tense and grip the leash you convey that you are also stressed. If you have the dog on a nose harness, you take away his ability to communicate and with it the last bit of control that could decrease stress.
It is important to, as our dog's leader, to lead by example – in the home and outside. When our dog reacts out of fear, it is crucial to remain calm, confident and centered. That does not mean to trivialize the problem, but it is up to the human(s) to set the stage for a different behavior, instead of letting the dog take the lead and return aggression with aggression, become tense when he does, make fast and loud noises and erratic hand movements. The dog can’t be in control if the human in charge is out if control.
Temple Grandin, in her book “Animals in Translation”, describes a study that showed that once monkeys had fears, it lingered and was contagious. Dogs that have strong and specific fears might need a long time before they feel safe. Because is lingers, and especially with rescue dogs that are newly adopted and don't have a trusted relationship with their people yet, it is important that the dog is not exposed to those triggers before it exists, he feels safe with them and has learned some coping skills. If he is exposed too soon, the fear resurfaces or intensifies.
Counter conditioning changes the association to the trigger and can work, but not always does. A dog who has a strong fear to something could have formed associations to all environmental details involved with it – the place, sounds, people, dogs, even the feel of the surface he was standing on. It doesn’t matter if a detail had something to do with the negative or traumatic experience or not. Any associated detail can trigger the fear reaction in a different context. With Will, it was any indoor training facility that shut her down.
The opposite is also true. Once an environment becomes a good and safe experience, all perceived details instill safety in different contexts. That is why it is so important that a dog feels safe with his owners.