We’ve all seen it, a dog straining at the lead, barking or pulling with everything they’ve got. It’s easy to call it ‘reactive’. But behind that word lies a story, one that only makes sense when we ask why.

Those barks, lunges, and sudden freezes are behaviours, not explanations. They tell us what is happening, not why. And without understanding the why, any solution is just guesswork.

When we lump every barking or pulling dog into one category, we miss the truth. Because what looks the same on the surface can come from entirely different motivations underneath. Let’s meet four dogs who look similar on lead, but whose reasons couldn’t be more different.

Dog 1: The Frustrated One

This dog is eager to greet, their body language full of anticipation. But when the lead prevents access, that enthusiasm turns to tension. The blocked drive to approach often spills over into barking, lunging, or pulling. The behaviour reflects frustration, a response that can intensify and present as aggression when unmanaged.

Dog 2: The Fearful One

This dog’s goal isn’t to engage, it’s to create distance. When the lead removes their ability to retreat, they feel trapped. Barking, freezing, or shutting down become their tools for making the threat go away. And when escape isn’t possible, fear can tip into defensive or offensive behaviours, the fight option. What we see as reactivity is, for them, an attempt to regain a sense of safety and control.

Dog 3: The Thrill Seeker

For some dogs, the on-lead tension itself becomes reinforcing. The excitement, the pull against pressure, and the surge of adrenaline turn each encounter into a self-fuelled loop. This is distance-decreasing behaviour, the dog moves toward rather than away from the trigger. It’s not driven by fear or frustration, but by over-arousal and anticipation. Over time, this pattern can become habitual, even enjoyable, for the dog.

Dog 4: The Mixed Bag

Many dogs show both ends of the spectrum, a mix of curiosity and caution. They might surge forward one moment and hang back the next. The restriction of the lead can amplify both impulses, intensifying frustration while deepening unease. These dogs need careful support to separate and balance those conflicting emotions.

Four dogs. Four very different motives. Four completely different paths to change.

Yet because it all happens “on lead,” we often throw one label at it and reach for the same generic fixes:

  • Sit and watch or give them a treat for looking at you, while the dog is already in full-blown flight mode and too stressed to learn.
  • Socialise them more, or until they’re overwhelmed and shut down.
  • Correct them, thus suppressing the outburst without addressing its cause.

The behaviour might stop temporarily, but suppression or surface-level management isn’t resolution, it’s only silence on the surface.

Looking Deeper: The Why Behind the Bark

To truly help these dogs, we need to look beyond what we see and ask better questions.

A strong framework for understanding behaviour comes from ethologist Nikolaas Tinbergen, whose 1963 paper ‘On Aims and Methods of Ethology’ introduced four key questions that form the foundation of modern behavioural science. Tinbergen proposed that to understand any behaviour, we must examine it from four angles: its function, cause, development, and biological roots.

These principles still guide effective practice today. As Karen Overall (2013) reminds us, behaviour is complex and context-driven, we can’t change what we don’t first understand.

1. Function – What purpose does this behaviour serve?

Is the dog saying “Let me at it!” or “Get me out of here?”
Behaviour always serves a function that makes sense to the individual. Understanding that purpose is the first step toward change.

2. Causation – What triggers it?

Is it another dog, a person, a sound, or a movement?
Dogs don’t react out of nowhere, there’s always a spark. Identify it, and you can manage the fire instead of fighting it blind.

3. Ontogeny – How did this behaviour develop?

Did it follow a bad experience? Is it a habit rehearsed over time?
Training isn’t about starting from scratch, it’s about reshaping what’s been learned.

4. Phylogeny – What role do breed and genetics play?

A Jack Russell isn’t a Cavalier King Charles. Their inherited instincts shape how they interpret and respond to the world. Working with those instincts, not against them, sets both dog and human up for success.

So… Is Lead Reactivity Really One Thing?

Not exactly.

It’s a convenient term that hides a range of emotions, frustration, fear, over-arousal, or a mix of all three, each needing a different approach.

And here’s the caveat: there are many other reasons dogs show what we call ‘lead reactivity’.

Some of these are distant antecedents, factors that set the stage long before the reaction happens. Pain or discomfort, inconsistent handling, lack of sleep, poor nutrition, hormonal changes, daily exercise or past trauma can all lower a dog’s ability to cope. Environmental influences like noise sensitivity, unpredictable surroundings, crowded spaces, or even the handler’s own tension on the lead can add to the emotional load.

Early experiences also matter deeply. Mal–socialisation during the early developmental stages of life particularly during the sensitive period for socialisation (around 3–14 weeks), can shape how a puppy perceives safety and novelty (Fox, 1971; Serpell & Jagoe, 1995). Limited handling, poor maternal care, or unenriched, chaotic environments during this time can make the world feel unpredictable and unsafe.

If the mother herself is highly stressed, she passes elevated cortisol levels through the placenta before birth and later through her milk while feeding. This early hormonal exposure can prime puppies to be more anxious or reactive, keeping their stress systems on high alert from the start (Foyer, Wilsson, & Jensen, 2013; Tiira & Lohi, 2015).

When this is followed by too much or too little exposure during the same developmental window, those early gaps often resurface in adolescence as heightened sensitivity, fear, or frustration on lead. This is when the puppy’s brain is rapidly developing, moving from dependence to awareness and social learning. Experiences during these stages, from the transitional phase through the socialisation window, set the emotional blueprint for how the adolescent dog copes with the world (Scott & Fuller, 1965).

When all these layers combine, what looks like ‘reactivity’ in the moment is often the result of accumulated stress and unmet emotional needs bubbling to the surface.

When we rely on one label, we end up with one-size-fits-all training and that’s not fair to the dogs who need understanding, not generalisation.

So if your dog barks, lunges, or freezes on lead, pause and ask why.

That simple question changes everything. Because the way we describe behaviour shapes how we respond to it. Understanding, not labels is where real progress begins.

References

Appleby, D. L., Bradshaw, J. W. S., & Casey, R. A. (2002). Relationship between aggressive and avoidance behaviour in dogs and their early experience. Applied Animal Behaviour Science, 84(1), 53–63. Fox, M. W. (1971). Behaviour of wolves, dogs and related canids. Harper & Row.

Foyer, S., Wilsson, E., & Jensen, P. (2013). Levels of maternal care in dogs affect adult offspring temperament. Applied Animal Behaviour Science, 152, 53–61. 

Overall, K. L. (2013). Manual of clinical behavioural medicine for dogs and cats. Elsevier.

Scott, J. P., & Fuller, J. L. (1965). Genetics and the social behaviour of the dog. University of Chicago Press.

Serpell, J., & Jagoe, J. A. (1995). Early experience and the development of behaviour. In J. Serpell (Ed.), The domestic dog: Its evolution, behaviour and interactions with people (pp. 79–102). Cambridge University Press.

Tiira, K., & Lohi, H. (2015). Early life experiences and exercise associate with canine anxiety. PLoS ONE, 10(11), e0141907. https://doi.org/10.1371/journal.pone.0141907

Tinbergen, N. (1963). On aims and methods of ethology. Zeitschrift für Tierpsychologie, 20(4), 410–433. https://doi.org/10.1111/j.1439-0310.1963.tb01161.x (Free English-language PDF available at https://www.esf.edu/biology/faculty/documents/Tinbergen1963onethology.pdf)