Dog Behaviour – What is Trigger Stacking?

This is a subject close to my heart because I have had a lot of adopted and rescue dogs that have suffered with nervousness and stress – brought on by exposure to various triggers; ( that is, something that causes the dog to experience, stress or fear).

A trigger which causes a dog to display signs of fear or stress can be unique to each dog, although there are common ones such as fireworks, strange people or dogs, visits to the vet, etc.  Other things might include walking in busy areas they have not experienced before – in the case of my dog; a visit to a beach which she had never done before.  Many dogs will have a unique set of triggers.

Each dog will also have a coping level, or ‘threshold’, as it is known in the field of behaviour.  This threshold represents the point at which a dog can no longer cope with feelings of stress or arousal.  In human terms we would describe it as being, ‘pushed over the edge’.

In dogs, once this point is reached they will enter a state of ‘fight’, ‘flight’ or ‘freeze’.  Some dogs may react aggressively (fight), others may bolt or attempt to pull out of their harness, or collar (flight), while some will simply shut down (freeze).  During any of these states it will be impossible to distract the dog and in most cases they will not take food or direction of any kind.

Crucially, this ‘threshold’ may be reached more quickly in some dogs than in others.  While some dogs may freak out at a dog in the distance, others may only reach breaking point when they have been tormented too long by a young child, for example.

But, what is ‘trigger stacking’?

This term refers to when a dog is subjected to many triggers all at the same time, or one after the other in quick succession.  While many dogs can cope easily with one or two triggers, once they begin to stack up, the dog can enter the fight, flight or freeze state.  These triggers may not always be negative, but if they cause the dog to be highly aroused, this then impacts on other stressors.  If a dog gets excited by being around other dogs, but is fearful of men – he may bite more readily if he has been aroused by playing with dogs in the park and is then approached suddenly by an unfamiliar male stranger.

When dogs are exposed to a trigger, their bodies activate a hormonal and neurological response.  Not surprisingly, this effect can last for many hours after a stressful event and even longer if the dog has experienced many triggers all in one go.  Dogs can even react to trigger stacking if they are exposed to events over a number of days, so you can see how stress can add up over time and potentially create allsorts of behaviour issues in some individuals.

This explains why some dogs can appear unpredictable in their reactions – you may have heard many dog owners exclaim, “He’s never done that before!” about an aggressive outburst.   This may be the case, but it shows that the dog only coped or tolerated a particular situation or trigger, he just didn’t have enough triggers occur beforehand to push him over the edge.

Consider the example of a dog walking down a busy street. He appears to have always coped with this, but then he experiences heavy traffic such as thundering lorries, which he is very unsure about. He then has to pass several strangers of which he is uncomfortable with.  Then he sees another dog, which he likes, but this further increases his arousal levels. Finally, an unfamiliar person walks up close to him.  This pushes him over the edge and he reacts aggressively.

Once these principles of trigger stacking are understood, it is easy to see how you can begin to manage situations and prevent your dog from ever reaching his coping threshold.  For people, with reactive dogs like mine, it’s an important concept to get to grips with, as understanding it, can help your dog to cope with the human world much better. Remember also, that it is not just negative experiences that can raise arousal levels, (like noisy traffic), but also things the dog enjoys such as playing with other dogs.

When it has already got to the point that your dog has reached his threshold, bear in mind that your dog has probably been feeling uncomfortable for some time before that.  Not all dogs behave this way; some dogs are more bomb proof and have very high coping thresholds, but all dogs will benefit from owners who always consider their dog’s mechanisms for coping in different situations and crucially, prevent them from encountering negative experience which may influence their future ability to deal with difficult situations.