Stress stacking and stress endurance

Have you wondered why sometimes, your dog reacts in situations she usually doesn’t react in? Why sometimes, she lunges at a passing cyclist, and other times she doesn’t? How sometimes she barks at running children, while usually she notices them, but seems okay with it? How usually she’s fine with passing a strange dog, but sometimes barks and snaps at him? 

We tend to assume that a stress diagram looks like this, even when several potential triggers happen simultaneously:

Graphic 1: one potential trigger at a time

Unfortunately, this diagram only depicts your dog’s (lack of) reactivity when encountering one potential trigger at a time. If your dog is slightly excited by cyclists, slightly worried about running children, and just a little concerned about meeting strange dogs, neither of these potential triggers will take your dog over her threshold when encountered on its own (graphic 1).

However, what happens if there is more than one trigger? Rather than not affecting each other, stress levels pile up when happening simultaneously. Grisha Stewart calls this phenomenon “stress stacking.” Consequently, the diagram looks like this:

Graphic 2: stress stacking (several triggers simultaneously)

Imagine you and your dog are walking past a playground with children playing, shouting and running. If a cyclist passes the playground at the same time that a strange dog walks towards you, your dog’s stress levels stack up and she is pushed over threshold by the combination of triggers (graphic 2). 

Challenging environments and default stress levels

Stress levels are not only individual triggers. Challenging environments (e.g. an agility trial environment, a dog show environment, the vet’s office, a busy city center etc.) have a higher default stress level (DSL) than everyday life. Hence, in a challenging environment with a high DSL, it takes less triggers to put your dog over threshold, or she may be pushed over threshold by one individual trigger she normally isn’t reactive about.

Imagine walking your dog past the busy playground of our first imaginative scenario. A strange dog and his owner walk towards you, but there is no cyclist and there are no other distractions. Your dog will be fine; the combination of children and dog will stress her slightly, but won’t put her over threshold. 

However, imagine you are taking your dog to see the vet. The vet’s office has a higher DSL than everyday life. If there isn’t only a strange dog in the waiting room, but also a mother whose children are playing catch, your dog will be pushed over threshold by the same two triggers she could deal with outside the vet’s office (graphic 3).

Graphic 3: default stress levels (DSL) in challenging environments 

For some fearful dogs and many young puppies who are just getting to know the world, a foggy day, dusk, dawn or darkness may constitute a challenging environment as well: silhouettes and shadows look different at night than during a day, and many puppies have to get used to this before they are okay with it.

The time factor

Stress levels are not only affected by triggers present at the moment, but also by things experienced a little earlier. In fact, the adrenalin level in your dog’s body (as well as in your own body, for that matter) reaches its peak 15 to 20 minutes after a stressful event rather than right away. The testosterone level goes hand in hand with the adrenaline level and also peaks 15 to 20 minutes after a stressful event.

Furthermore, it takes a while for a dog’s (or human’s) nervous system to calm down again. Depending on the intensity of the stressful experience, the adrenalin level may take up to a week (!), the cortisol level up to 40 days (!) to go back to normal (graphic 4). (1)

Graphic 4: the short- and long-term development of hormone levels

Hard to imagine? Let’s look at another example (this example was suggested by Anne Lill Kvam during a dog trainer seminar last weekend): imagine you’re driving home from work, and someone takes your right of way. A little later, the same thing happens again. You’re slightly annoyed, but glad you avoided an accident. 15 minutes later, you unlock the door to your apartment and are greeted by your girlfriend with the words: “you didn’t forget the groceries, did you?” This innocent question puts you over threshold because your adrenalin and testosterone level have just reached their peak, making aggressive reactions more likely.

Practical implications

– Be patient – with yourself, with your dog, and with others. They probably can’t help their behavior: their hormone levels might be agitated. 

– Remember the importance of giving your dog frequent breaks, especially in stressful situations. (And give yourself breaks, too.)

– Introduce one new stimulus at a time when training new behaviors. 

– Lower criteria when practicing a new behavior in a challenging environment.

– If you have a performance dog, work on lowering the default stress level in challenging environments (such as the agility trial environment) in order to maximize performance. This should be done separately from working on other behaviors such as agility obstacles. Keeping the DSL low in challenging environments is an independent skill-set and should only be combined with other tasks after it has been established as a reliable foundation. 

(1) Thank you, Anne Lill Kvam, for pointing this out!

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