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Trigger Stacking in Dogs: The Cumulative Effect

Updated: Jan 23, 2021

chocolate Lab dog with open mouth and wide eyes looking surprised

Imagine that you’re having a bad day. You woke up late for work, skipped breakfast, rushed out the door, and got stuck in traffic. A stressful hour later you arrive at the office to find that not only has a work deadline been moved up, but you’re expected to take on another project as well. Eight long hours later you finally return home, where your spouse reminds you that you had promised to fix a clogged sink. You snap at your spouse and storm out of the room.

Now imagine that your day went differently. You woke up on time, had a leisurely breakfast, avoided traffic, and had a good day at work. Now you return home to the request to fix the sink. You might not have the time or inclination to comply then and there, but at the least, you’re not likely to have snapped. What does this have to do with dogs? Everything.

Dogs experience cumulative stress, too. Take a dog who is not inclined to snap or bite under normal circumstances. The dog is feeling unwell. Because a vet appointment is scheduled at 10 a.m., he misses his usual morning two-mile run. The vet has requested that the dog not be fed before the appointment, so the usual 9 a.m. feeding is skipped. The dog has always been nervous when being examined, and today is no different. Blood must be drawn so the dog is muzzled, which adds to his stress. Afterwards, at home, a workman shows up to give an estimate. The dog, who is afraid of men, barks nervously and paces throughout the visit. Later in the day, a friend brings their dog over to play. The dogs have played together many times. The visiting dog has a tendency to be rough and pushy, but the dogs read each other’s signals well. Today, however, when the visiting dog makes a rude move, the other dog bites and a fight breaks out. This is the cumulative effect in action, and in professional training circles, we call this trigger stacking.

Sometimes it’s not an accumulation of stress that leads to an eruption, but a buildup of triggers. Let’s say a dog has a mild resource guarding issue. She doesn’t normally bite, but if approached when in possession of a valuable resource, her head will lower over the object, and she’ll growl. She won’t, however, bite if her owner reaches to remove the object. The dog also has a possessive feeling about the family’s bed. She’ll sometimes jump on the bed and growl at the other dog to keep him away, and she’s even growled at the husband from her lofty vantage point; but again, she will not bite. The dog is generally nervous around men wearing hats, and tries to stay away from them. One day, friends are coming to visit. The dog is given a bone to keep her busy. She takes the bone to the bedroom and jumps up on the bed to enjoy it. The visitor, a man wearing a hat, needs to use the phone. Because the hall phone is not working, he is instructed to use the one in the bedroom. He walks in and decides to get the dog off the bed. He reaches to move the dog’s bone, thinking he’ll toss it on the floor and the dog will follow. The dog bites his hand.

In this example, the dog would not have bitten in any of the individual circumstances, had they occurred separately. But stack them all together, and the dog’s buffer of calmness was eaten away bit by bit, until finally the raw nerve that was exposed pushed the dog over threshold and into biting.

So what can we do about trigger stacking? Practice awareness. If your dog has specific triggers that cause aggressive behavior, take care that they do not end up combined. Pay attention when the day becomes stressful, not just for you, but for your dog. Has your dog’s physical needs been met? Is he “crankier” than usual, for lack of a better word? If so, it might not be the best day to take him to an event around a lot of people, or have a play date. Be especially aware of things like skipped exercise, skipped meals, vet visits, and fear issues around strangers, other dogs, new environments, or whatever makes your dog nervous. Staying aware of cumulative stress, not only in ourselves but in our dogs, can prevent problems before they begin.


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