Caregivers often struggle to understand their reactive dogs. From a human perspective, reactivity appears unpredictable and disproportionate to the circumstances.
Yet, from the dog's perspective, reactive episodes drain emotional energy and block access to learning and thinking. They are the result of a sequence of automatic stress responses in the dog's physiology.
What we see on the surface reflects the adaptive changes within the dog's body. The sympathetic nervous system is activated, mobilizing the dog's fight-or-flight response. Stress hormones are released, the HPA axis is activated, and heart rate, blood pressure, and respiration increase.
If the dog's biology can handle the stress response and complete the stress cycle, then he'll recover and return to baseline when the trigger is no longer present.
But some dogs are unable to recover; they can't bounce back to baseline.
In other words, stress itself isn't the problem. Lingering stress is. Some dogs startle, recover, and move on. Others escalate and stay "up," even after the trigger is gone. Their nervous systems don’t reset. Shawna Baskette, How Stress Physiology Drives Reactivity in Dogs
It's important for caregivers to comprehend the long-term impact of chronic, or lingering, stress on the dog's brain, nervous system, physical pain, capacity to learn, and mood state.
Programs that address reactivity through behavior modification alone may achieve short-lived success, but they ultimately fail because they address only the superficial effects of the survival instinct.
Reactivity is appropriately addressed with dogs, as with humans, through gentle, well-managed exposures, secure attachment to a trusted caregiver, and recovery through completion of the biological stress cycle.
Please see the following two articles for a more detailed explanation of how reactivity feels for dogs:
Stress Physiology and Reactivity
Responses