BehaviorAggressionLeash & Barrier ReactivityTrainingPositive ConditioningResource GuardingStress Signals Causes of Reactive Dog Behavior and How to Train A Reactive Dog What is a reactive dog? If your dogs "go off" or "lose it" in certain circumstances, they may benefit from training focused on their reactive behavior. By Pat Miller, CBCC-KA, CPDT-KA - Published: October 10, 2003 Updated: