Dogs are like humans in many ways, including their biology. An important biological element that we share is the 10th cranial nerve, also known as the vagus nerve. The vagus nerve connects the brain to the body and helps regulate the autonomic nervous system in both humans and dogs. When all is going well our ventral vagus is in charge, and we have feelings of safety and comfort. Our breathing and movements are easy and joyful. We are in a state of flow, showing playful behavior while interacting with others. When we start to sense fear or perceive danger, this system also helps mobilize us into fight or flight.
When fight or flight aren't an option, the nervous system digs a little deeper into our evolutionary biology and the dorsal vagus takes over, much like it would in a reptile who shuts down important bodily functions to become completely immobilized. I'm not going to go into the vast details and complexities of Dr. Stephen Porges' Polyvagal Theory, but if you aren't familiar with it, I would suggest listening to this interview which will give you a good overview.
Because the vagus nerve is connected to many different parts of the body, we can see physical expressions that give us clues to reading a dog's vagal tone:
1. Facial Expression: Does your dog's face appear calm and relaxed? The muscles in the face are connected to the ventral vagus; therefore tense, tight or rigid muscles in the face can indicate fight/flight and even freeze. Hopefully you can tell when your dog's face is "soft." He might appear puppy-like, with floppy ears (depending on the ear-type). Read on for more clues...
2. Eye Gaze: Do your dog's eyes and gaze, including eyelids, appear soft and curious? Or is his gaze hard and fixed? If your dog's eyes are "fixed" on a prey object, he may be in a state of flow, about to engage in the hunt. If your dog's eyes are fixed on something that is causing him more stress than he can handle, you might see hackles raise and his sympathetic nervous system could begin to engage fight/flight mode.
3. Head Tilt: Does your dog have that adorable head tilt? If so, he is "plugged in" to his social engagement system. Even if he doesn't have a very active head tilt, when he's feeling relaxed his head probably tilts very slightly to one side or the other. This is a subtle tip for you! And when you combine these first three points: the face, eyes and tilt of the head, you have a lot of information about the dog's state of mind/state of body. His ears will be searching for sounds as he scans the environment. He's probably also using his nose to search for information that his gut can process on an emotional level. Nose-twitch = happy doggy!
4. Swallowing: Will your dog take food? If not, he's probably stressed. I don't suggest throwing food in your dog's face when he's feeling stressed around other dogs, this can add too much energy to the situation. But say, for example, you are at the vet's office and want to know if your dog is still socially "online," offer him a treat and see if he will eat it. One of our fundamental exercises in Holistic Dog Training starts with the question: "Will the dog take food?" And if you think about times that you have experienced extreme stress, you know that eating is the last thing on your mind. Same for your dog. But if he's drooling buckets for treats, you should be good to go!
5. Breathing/Barking: Is your dog in control of his breath? You can tell this if you have trained a bark-on-command. The vagus nerve has control over the esophagus, bronchi, pharynx, and larynx. When your dog has a nice ventral-vagal tone, she will be able to produce a deep, metered, guttural bark. If your dog has a high-pitched, frantic bark, she's probably in a state of stress and may be moving towards fight or flight behaviors. Working to both deepen the bark and calm the rhythm of the bark, helps to tone the vagus and give your dog a sense of well-being. If she can't bark at all, your dog may be experiencing a stressful situation and entering some stage of shut-down. And as Mos Def tells us, "Quiet dog bite hard."
6. Heart Rate: I'm not sure I would use a heart-rate monitor on my dogs, but as I'm writing this, thinking it could be an interesting experiment! Just know that heart rate variability is a great indicator of stress resilience, and that when your dog has nice vagal tone his heart rate will reflect that. Think about times when extreme stress has caused your heart to race and you will begin understand how the vagus and the heart play a role in either feeling calm, or getting mobilized to deal with danger. Even though we may not measure it directly, your dog's heart is where her head is, when it's not in the gut.
This is really just scratching the surface when it comes to the vagus and Polyvagal Theory, but I believe it gives us a jumping off point. Following up I hope to delve into some specific tool you can use to help tone your dog's vagus, which will calm his nervous system and build up his ability to cope with stress. For more information please see the work of Dr. Stephen Porges. And thank you also to Deb Grant and her workshop, Dancing in Vagus, which inspired this post!
Be well, and stay "toned."