Reactivity refers to canine behavior whereby a dog is over aroused by something in the environment. For some dogs it may be the sight of another dog. For others, it may be a child riding a bike or a jogger passing by the window. Or any number of things.
The behavior response includes an abrupt increase in tension and arousal, which may be manifested in repeated barking and/or lunging, a display of teeth designed to be threatening/intimidating, or various other behaviors which guardians often perceive to be aggressive.
The next thing to understand is the emotional motivation of the behavior.
(Issue 48, May 2021, pp.28-31). Read article