Glossary

Reactivity

A dog's exaggerated reaction, such as barking, lunging or freezing, to a trigger like other dogs, people or noises.

Also called: reactive dog, dog reactivity, over-reacting

A reactive dog responds to everyday triggers, such as other dogs, strangers, bikes or sounds, with intense behavior: barking, lunging, growling or freezing. The cause is usually fear, frustration or overexcitement, not meanness.

Reactivity is a description, not a diagnosis, and it is not the same as aggression. Many reactive dogs never bite, though some may if pushed too far. The first step is to work out the trigger and the distance at which the dog begins to react, and to keep the dog under that threshold while training.

Punishing the display can suppress the warning without changing the feeling, which makes behavior less predictable. Reward-based plans such as desensitization and counter-conditioning help. Because pain and illness can contribute, see a veterinarian first, and consider a qualified trainer or behaviorist.

Last reviewed November 8, 2026

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Related terms

Leash reactivity Barking, lunging or growling at other dogs or people when on a leash, often from fear or frustration at being unable to move freely. Threshold The point at which a dog goes from noticing something to reacting to it, often described as a distance or an intensity. Trigger stacking Several stressful events building up in a short time so that a dog that would normally cope reacts strongly to a small extra trigger. Desensitization and counter-conditioning A training plan that exposes a dog to a fear trigger at a level it can handle while pairing it with something good, to change how the dog feels.