What‘s the difference between reactivity and aggression in dogs?

The short answer!

Reactivity is emotional flooding, aggression is intentional harm. Reactive dogs are overwhelmed and trying to create distance, aggressive dogs are determined to cause damage.

The distinction sits in intent and emotional state. A reactive dog has lost emotional control, an aggressive dog is strategically pursuing conflict.

Reactive dogs:

Early distress signals: whale eye, tucked tail, backing up, displacement behaviours (yawning, lip licking)
Visible arousal build-up before erupting into barking
Difficulty being redirected mid-outburst because an emotional response has hijacked their processing abilities
Goal is creating distance from the trigger

Aggressive dogs

Minimal escalation, may go from calm to bite-behaviour quickly
Calculated behaviours: stalking, sustained direct eye contact, forward body weight
Controlled rather than panicked presentation
May skip obvious warning signals

The overlap problem

Any reactive dog can bite if pushed past threshold. If distance-creating signals (barking, lunging) are ignored and the trigger keeps approaching, they may escalate to a defensive bite. This isn't true aggression, it's a cornered animal protecting itself, but the outcome is the same (1).

Research shows dogs with high aggressive reactivity also demonstrate impaired self-control in other contexts, suggesting overlap in underlying arousal regulation rather than clear-cut (reactive/aggressive) categories (2).

What to keep an eye on

Watch what happens after the outburst. Reactive dogs relax when distance form the trigger increases, and often show stress signals afterwards (panting, drooling, difficulty settling). Aggressive dogs may maintain intensity even when the threat retreats, and often return to baseline behaviour quickly with no visible signs of stress or discomfort.

References

Arhant C, Bubna-Littitz H, Bartels A, Futschik A, Troxler J. Behaviour of smaller and larger dogs: effects of training methods, inconsistency of owner behaviour and level of engagement in activities with the dog. Appl Anim Behav Sci. 2010;123(3-4):131-142. Available from: https://doi.org/10.1016/j.applanim.2010.01.003
Gobbo E, Zupan Šemrov M. Dogs exhibiting high levels of aggressive reactivity show impaired self-control abilities. Front Vet Sci. 2022;9:880766. Available from: https://pubmed.ncbi.nlm.nih.gov/35400110/

This content is for general information only and does not replace veterinary advice. Supplements and nutritional products are not licensed veterinary medicines. Always speak to your vet before making changes to your dog’s diet, supplements, or care routine.

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owners also ask

Why is my dog only reactive on the lead?

The lead removes your dog's escape option, and when they're unable to run away from something scary, they bark and lunge to make it leave instead.

How to calm a reactive dog

In the moment, create distance from the trigger immediately. In the long-term, structured desensitisation and counter-conditioning work are most effective.