“Dogs live in the moment” but what does that actually mean?

We often hear that dogs live in the moment. There's some truth in that phrase, but scientifically, it's far too simplistic. Dogs absolutely remember. They learn from previous experiences and they form powerful associations. 

So a dog who had a frightening experience six months ago can absolutely behave differently today because of what they learned six months ago. But there's an important distinction between what shaped a behaviour and what triggered a behaviour right now.

When I'm investigating an apparently sudden aggressive response, one of my most important questions is:

What happened immediately before it?

In behavioural science, we often describe this as the antecedent (the event, stimulus or change that precedes the behaviour). A dog doesn't generally spend the afternoon thinking:

"I was annoyed by something at 9am, so I'm going to bite someone at 4pm."

Instead, something happening now pushes the dog's nervous system beyond its threshold. That "something" might be obvious. A hand reaches towards them. Someone tries to remove an object. Another dog approaches. A child hugs them. Someone bends over them. They hear a particular noise. They are prevented from moving away. But sometimes the trigger is extraordinarily subtle. It might be a change in someone's posture. A particular smell.

Someone approaching a part of their body that has previously been painful. The anticipation of being handled. A noise we haven't even noticed. Or it may be something happening inside the dog's body: pain, nausea, gastrointestinal discomfort, itching, fatigue or another unpleasant physical sensation.

But what about something stressful that happened earlier that day? This is where trigger stacking comes in.

Imagine a dog's threshold as a line. Normally, encountering another dog at 20 metres might not be enough to push them over it. But today they slept badly. Then there was construction outside the house.Then the postman arrived. Then they had an uncomfortable car journey.

Then they encountered two dogs on their walk. Their level of arousal or stress may already be considerably higher than usual. Now another dog appears at 20 metres.Yesterday they coped.

Today they explode. The final dog didn't necessarily cause all of that stress. It was simply the trigger that pushed an already loaded system beyond threshold.

This phenomenon is commonly called trigger stacking: multiple stressful or arousing experiences accumulate so that a dog becomes more likely to react strongly to something they might ordinarily tolerate.

So yes, what happened at 10am three years ago can influence what happens at 6pm today

But it changes the threshold. It doesn't necessarily explain the immediate target of the behaviour. There is still usually something occurring at 6pm that the dog's nervous system is responding to.

Think of it as: HISTORY → STATE → TRIGGER → RESPONSE

History: Genetics, early development, previous learning, previous frightening or painful experiences.

Current state: Sleep, stress, arousal, hormones, hunger, illness, pain, gastrointestinal discomfort, previous triggers that day.

Immediate trigger: Something the dog perceives, anticipates or physically experiences.

Behavioural response: Freeze, avoidance, barking, growling, lunging, snapping or biting.

Dogs live in the present with a nervous system that has been shaped by the past. And this is particularly important with aggression. Aggression is not a diagnosis.It's behaviour. Frequently it is a response to perceived threat, fear, frustration, conflict, pain or anticipated discomfort. Dogs respond in the moment, but they don't arrive in that moment without a history. Their past experiences determine what they have learned. Their physical and emotional state determines how much they can cope with today. And something occurring or anticipated in the present usually determines when that response finally happens.