Calling a dog “reactive” describes someone’s impression of the dog’s behavior, but it does not identify what the dog is doing, why it is happening, or what training approach is appropriate. If someone tells me, “My dog is reactive,” I still do not know what the dog does.
Does the dog bark? Lunge? Whine? Pull toward other dogs? Retreat from them? Stare? Growl? Spin at the end of the leash? Try to make contact? Bite? Does it happen with every dog, only certain dogs, only on leash, only near the house, only behind a fence, or only when another dog gets too close?
“Reactive” may be convenient shorthand, but it is not an explanation of behavior. Before deciding how to train the dog, we need to get underneath the label and determine what is happening.
Is “reactive dog” a scientific term?
“Reactive dog” is not a standardized scientific diagnosis or a single scientifically defined category of dog.
The word reactivity certainly appears in scientific research, but that is different. Researchers must define what they mean by the term and specify which observable behaviors count as reactivity in a particular study. That distinction is important.
A 2024 paper in the Journal of Applied Animal Welfare Science examined how people understand canine “reactivity” and noted that there is no consensus in either scientific literature or ordinary usage about exactly what the term encompasses. The researchers found a complex and sometimes contradictory mixture of ideas involving both characteristics of the dog and human perception. PubMed
A 2025 shelter study made the problem even more explicit. The authors wrote that canine reactivity is not precisely defined and recognized that judgments about reactivity involve both the dog's behavior and the human observer's perception of what constitutes appropriate behavior. The researchers therefore had to create a specific definition for their own study. MDPI
That is how science is supposed to work. If you are going to measure something, you first have to say exactly what counts. Everyday conversations about “reactive dogs” usually do not do that.
Can two people look at the same dog and disagree about whether the dog is reactive?
Absolutely. Part of the label exists in the eyes of the beholder. One owner may consider barking twice at another dog normal excitement. Someone else may call the same dog reactive. One trainer may reserve the term for intense barking and lunging. Another may include whining, leash pulling, staring or difficulty disengaging.
Experience also changes how people interpret canine behavior. Research has shown that people's ability to identify emotional states in dogs varies with their experience with dogs, and other work has found substantial difficulty matching behavioral and emotional labels with their intended definitions. PMC
This does not mean behavior is merely subjective. The dog really did something. The problem is that the label and the behavior are not the same thing. “Barked six times, pulled hard toward the other dog, and stopped barking when the other dog was about 40 feet away” gives me information. “He was really reactive today” gives me someone's summary of that information.
Those are not equivalent.
Does a reactive dog mean a stressed or frightened dog?
No. Stress or fear may be reasonable hypotheses in some cases, but the label “reactive” does not establish either one. There is a popular explanation that reactive dogs react because they are struggling, frightened, uncomfortable or stressed. Sometimes that may be exactly what is happening. Sometimes it may not.
The same outward behavior can occur under very different circumstances. A dog pulling and vocalizing toward another dog might be attempting to increase distance. Another might be intensely trying to approach. Another might have a history of conflict with certain dogs. Another may be highly aroused by movement. Another may have learned a particular leash sequence through repetition. Physical discomfort, developmental history, genetics, previous encounters, restraint, owner behavior and competing motivations can also be relevant. The behavior is evidence. The proposed emotional or motivational explanation is an inference. That distinction is fundamental.
Isn’t my dog communicating something when he reacts?
Possibly, but saying “behavior is communication” can also become another shortcut if we stop there. Animals certainly use behavior to communicate. Growls, postures, vocalizations, orientation, approach and withdrawal can convey information to other animals and people. But observing behavior does not automatically tell us its cause, function or the dog's complete internal state.
A bark is something the dog did. Calling that bark a communication of fear, frustration, threat, excitement or stress requires additional evidence.
Classical ethology gives us a useful warning against overly simple explanations. Niko Tinbergen argued that understanding behavior requires asking different kinds of questions, including questions about immediate causation, development, function and evolutionary history. Those questions cannot simply be collapsed into one convenient explanation. ScienceDirect
So my preference is to say: Behavior gives us information. It does not interpret itself.
Does “reactive” mean aggressive?
No. “Reactive” and “aggressive” should not be treated as interchangeable words. A dog may bark, whine, leap around, pull or display conspicuous postures without committing violence. Another dog may give relatively little display and then bite.
That is one reason catch-all labels can become dangerous. Loudness and spectacle can attract human attention, while the behavior that matters most for safety may be something else entirely.
A recent 2026 study demonstrates the problem particularly well. Researchers first had to develop a working definition of a “dog reactive dog.” Their definition included barking, growling, snarling, lunging, snapping, nipping, biting, whining and certain postures. When they analyzed 1,360 complete behavioral profiles, those behaviors did not form one uniform phenomenon. The analysis produced different components and four behavioral subtypes with differing escalation risk. ScienceDirect
In other words, even after researchers deliberately created a category called “dog reactive dogs,” the dogs inside that category were behaviorally heterogeneous. That is exactly why the label should begin an investigation rather than end one.
If “reactive” does not explain the problem, what should I describe instead?
Describe what the dog does and the conditions in which it happens.
If I were assessing the problem, I would want to know things such as:
- What does the dog do?
- What is the dog responding to?
- How close is the other dog, person, bicycle or other stimulus when the behavior begins?
- Does distance change the behavior?
- Does it happen on leash, behind fences, through windows or when the dog is loose?
- Does it happen with every dog or only certain dogs?
- Does the direction of approach matter?
- Does movement matter?
- Does the dog's behavior differ with different handlers?
- What happens immediately before the behavior?
- What happens immediately afterward?
- How easily does the dog disengage?
- How quickly does the dog return to ordinary activity?
- Has the pattern recently changed?
- Are there physical or medical concerns that warrant veterinary evaluation?
Now we have something we can investigate.
“Reactive” cannot answer any of those questions.
Why can two dogs that look reactive need completely different approaches?
Because similar visible behavior can be produced by different combinations of conditions. This is one of the ideas that experienced working-dog trainer Armin Winkler emphasizes from a different training tradition. Winkler rejects the idea that dogs deliberately cheat, insult the handler or knowingly choose to “do wrong.” But importantly, he does not replace that moral explanation with a single emotional explanation.
In his discussions, you will learn performance failures can involve incomplete teaching, competing motivation, arousal, fatigue, genetics, physical limitations, environmental conditions or consequences created by previous training. No dog has EVER knowingly done something wrong.
That is a much more useful way to think about a dog labeled reactive. The alternatives are not simply: “He is a jerk.” Or. “He is stressed.”
Both can prematurely stop the investigation.
The useful question is: What combination of variables best explains this particular dog's behavior in this situation?
Is reactivity a tame problem or a wicked problem?
You cannot tell from the word “reactive.” I have written elsewhere about the difference between tame and wicked problems in dog training. A tame problem has a reasonably clear target, established procedures and measurable outcomes. A wicked problem involves interacting variables, incomplete information, changing conditions and competing explanations. (Sam the Dog Trainer)
The distinction comes originally from the work of Horst Rittel and Melvin Webber on complex problem solving. Wicked problems resist single, final solutions because the definition of the problem and the attempted solution interact. DOI
Some dog problems called “reactivity” may turn out to be comparatively narrow. Others involve developmental history, physical state, genetics, learning history, environmental management, social relationships, owner handling and recurring circumstances that cannot be reduced to one technique.
My own rule is simple: A behavior label is not an explanation, and the training exercise should follow from the assessment rather than from the label.
Should I yell at or punish my dog for reacting?
Getting angry at the dog is not a substitute for determining what happened or teaching the dog what you want instead. Calling the dog stubborn, bad, dominant or a jerk adds a moral judgment without explaining the behavior. Yelling after an episode may also create additional conflict while doing very little to clarify what the dog was supposed to do differently. But the opposite oversimplification is also unhelpful. We should not reason that because all “reactivity” represents stress, every possible interruption or consequence is therefore inappropriate. We have not established that all dogs carrying this label are in the same state or behaving for the same reason.
Winkler makes a useful distinction between teaching and correction. In his framework, teaching establishes the behavior first; correction concerns interrupting a competing behavior after the relevant skill is known; retaliatory “payback” after the fact is something different again. No dog has EVER knowingly done wrong.
Whatever training philosophy someone uses, that distinction exposes an important error: you cannot fairly say the dog “refused” a behavior until you have established what the dog learned, under what conditions it was learned, and whether the behavior was accessible under the present conditions.
What should I do first if my dog is called reactive?
Start by managing safety and collecting better information. Creating additional distance can be an excellent immediate decision when a dog is escalating around another dog, person or moving object. Distance can reduce conflict and give the owner more options. It does not require us to pretend that we already know why the dog reacted. Likewise, bringing useful rewards may help you reinforce workable behavior when the dog can respond to you. But neither treats nor distance constitute a diagnosis.
The next job is to identify the smallest conditions under which the dog can encounter the relevant situation without the problem escalating, then compare those conditions with the situations where the behavior breaks down. Assessment comes before prescription.
When does professional assessment make sense?
Professional assessment becomes especially useful when the behavior is worsening, includes biting or attempted biting, creates a safety problem, varies dramatically between situations, prevents ordinary activities, or does not improve despite sensible management and training.
Veterinary evaluation also makes sense when there has been a significant change from the dog's previous baseline or there are possible physical or medical contributors.
An in-home assessment can be particularly useful because behavior described as reactivity frequently depends on context: the neighborhood, fences, doorways, other household dogs, the owner's handling, familiar walking routes and the distances available in the dog's actual environment. The purpose of assessment is not to attach a more impressive label. It is to discover which variables matter.
“Reactive” should start the assessment, not finish it
If you tell me your dog is reactive, I know that someone has seen behavior that seemed unusually intense or problematic. I do not yet know what the dog did, why the dog did it, what state the dog was in, whether the same thing happens elsewhere, or what intervention is appropriate. That is the distinction I want dog owners to remember.
“Reactive” is a catch-all description. It is not a root cause.
Start with the observable behavior. Compare contexts. Separate what you know from what you think might explain it. Then build the training plan from the evidence. If your dog has a similar problem and you are not sure what changes between the situations where the behavior succeeds and fails, an in-home assessment can help identify the relevant variables and build the training plan from there.
You can learn more about working with me at SamTheDogTrainer.com.
Glossary
Reactive / Reactivity: A broadly used descriptive label for conspicuous or intense responses to stimuli. In ordinary dog-training use, it has no single standardized definition.
Operational definition: A precise statement of what will count as a particular phenomenon for purposes of observation or research.
Observation: A description of what occurred without assigning a cause, such as “the dog barked and pulled toward another dog.”
Inference: A conclusion drawn from observations, such as the hypothesis that distance, restraint, fear or competing motivation contributed to the behavior.
Hypothesis: A proposed explanation that can be tested against additional observations or evidence.
Context: The surrounding conditions in which behavior occurs, including location, distance, people present, restraint, other animals and preceding events.
Tame problem: A problem with a relatively clear definition, established methods and measurable outcomes under appropriate conditions.
Wicked problem: A complex problem involving interacting variables, incomplete knowledge, changing circumstances and no single final solution.
Bibliography
Gilchrist, R., & Wynne, C. D. L. (2025). Reducing human-directed kennel reactivity in shelter-housed dogs. Pets, 2(2), 17. https://doi.org/10.3390/pets2020017. MDPI
Rittel, H. W. J., & Webber, M. M. (1973). Dilemmas in a general theory of planning. Policy Sciences, 4, 155-169. https://doi.org/10.1007/BF01405730. DOI
Stephens-Lewis, D., Johnson, A., Turley, N., Naydorf-Hannis, R., Scurlock-Evans, L., & Schenke, K. C. (2024). Understanding canine “reactivity”: Species-specific behaviour or human inconvenience? Journal of Applied Animal Welfare Science, 27(3), 546-560. https://doi.org/10.1080/10888705.2022.2147007. PubMed
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. Wiley Online Library
Van Haevermaet, H., Soulsbury, C. D., & Mills, D. S. (2026). Reactive and risky: The behavioural structuring of “dog reactive dogs.” Applied Animal Behaviour Science, 299, 106961. https://doi.org/10.1016/j.applanim.2026.106961. ScienceDirect
Winkler, A: https://rivannak9services.com
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