Wormald, Lawrence et al. (2016) — Applied Animal Behaviour Science
Physiological Stress Coping and Anxiety in Greyhounds Displaying Inter-Dog Aggression
Published: July 9, 2026
A dog who appears calm in an open field, who does not react visibly to noise, who passes every surface-level anxiety assessment you put in front of them — can still be a dog whose physiology is primed for aggression toward other dogs. A study of greyhounds has produced findings that challenge some of the most commonly used assumptions in canine behaviour assessment. And the mechanism it points to is one that most owners never see directly. 🐾
Researchers D. Wormald, A. Lawrence, Gabrielle Carter, and A. Fisher measured greyhound behaviour across three separate contexts: an open field and noise stimulus test designed to capture anxiety-related behaviour, a routine blood donation procedure during which physiological stress markers were recorded, and a formal aggression test involving exposure to an unfamiliar dog. The design was deliberate — stress and anxiety were measured in a context entirely unrelated to aggression, and aggression was measured separately. The question was whether the two connected.
What the Physiology Revealed
The aggression test divided the dogs into two groups: those who passed without displaying aggression toward the unfamiliar dog, and those who failed by displaying inter-dog aggression. When the researchers compared the physiological data collected during the blood donation procedure — a stressful but entirely non-aggressive context — the differences between the groups were significant and consistent.
Dogs who later displayed aggression had a significantly greater increase in salivary cortisol during the bleeding procedure. Their initial heart rate was elevated compared to non-aggressive dogs. And their heart rate variability showed markedly different patterns — with aggressive dogs displaying significantly lower variability in both high and very low frequency spectra. Lower heart rate variability is a well-established physiological marker of reduced autonomic flexibility — a nervous system that is less able to shift efficiently between states of activation and recovery.
In plain terms: the dogs who later became aggressive toward an unfamiliar dog were, during an entirely unrelated stressful experience, showing a physiology that was harder to activate, harder to calm, and less flexibly regulated than dogs who did not aggress. The stress coping system was different — and that difference predicted behaviour in a completely separate context.
The open field and noise stimulus behavioural test showed no difference between the groups. If you had only observed these dogs in that assessment, you would have seen nothing to distinguish the dogs that would later aggress from those that would not. The signal was physiological, not behavioural. And it was invisible to standard observation.
What This Changes About Aggression Assessment ⚠️
The implications for how we assess and predict inter-dog aggression are direct. Behavioural observation in controlled settings — which is how most aggression assessments work — captures what a dog does when the conditions are structured and the stressors are visible. It does not capture the dog’s underlying physiological stress coping capacity, which this research suggests is a more fundamental predictor of aggressive response.
A dog with a dysregulated stress response system does not need an obvious trigger to be primed for aggression. They arrive at any social situation already carrying a physiological baseline that responds more intensely, recovers more slowly, and tolerates less before tipping into reactive behaviour. That baseline is not visible in their resting demeanour. It is not captured by watching them walk through an open field. It is revealed only under conditions that actually load the system.
This is why aggression in dogs so often appears to come from nowhere. The owner sees a dog who seems fine. Who seemed fine yesterday. Who seemed fine all morning. And then, in a specific moment of accumulated physiological load, the threshold is crossed — and the behaviour that results looks sudden because the internal build-up that preceded it was never observed.
Reading the Whole Dog Not Just the Visible Behaviour 🐕
At Zoeta Dogsoul, this research reinforces a foundational principle of NeuroBond: genuine attunement is not limited to reading visible behaviour. It includes reading the physiological state beneath the behaviour — the tension in the body before the growl, the subtle elevation in arousal before the lunge, the accumulated load that has been building since morning and has nothing to do with the dog they just passed on the street.
A dog with compromised stress coping capacity needs a relational environment that actively reduces load rather than adding to it. Consistent structure. Predictable routine. An owner whose own nervous system regulation is stable enough to provide a calm reference point rather than an additional stressor. These are not soft considerations. They are the physiological context within which aggression either builds or dissipates.
The Invisible Leash between dog and owner is most relevant precisely in these moments — the moments before the visible behaviour arrives. A dog who is physiologically loaded but relationally anchored has somewhere to orient. A dog who is physiologically loaded and relationally adrift has only the reactive system left to work with. What you build in the calm determines what is available in the storm. 🐾
Source: Wormald, D., Lawrence, A., Carter, G. L., & Fisher, A. (2016). Physiological stress coping and anxiety in greyhounds displaying inter-dog aggression. Applied Animal Behaviour Science. Published July 1, 2016.
