In a nutshell the Polyvagal approach focuses on how function and structure changed in the vertebrate autonomic nervous system during evolution. The theory is named after the vagus, a major cranial nerve that regulates bodily state. As a function of evolution, humans and other mammals have a “new” vagal pathway that links the regulation of bodily state to the control of the muscles of the face and head including the middle ear muscles. These pathways regulating body state, facial gesture, listening and vocal communication function collectively as a Social Engagement System.
Because the Social Engagement System is an integrated system, interventions or tools influencing one part of this system can impact the other parts. Thus, shifts in our physiological state ranging from calmness to losing your temper will be reflected in your ability to process and understand human speech. So essentially we can use listening as a portal into our nervous system via the vagus.
The middle ear muscles are the smallest muscles in the body. These tiny muscles control the rigidity of the small middle ear bones which effects what frequencies of sound which make it into our brains and hence what we hear. These muscles are used to promote the dampening of low frequency noises and the extraction of human speech. The middle ear muscles evolved in mammals in parallel with their ability to vocalize. Most likely an evolutionary adaptation to survive in an environment dominated by reptiles. The ancient reptiles did not have detached middle ear bones and used bone conduction to hear so communicated in low frequencies. While mammals use air bone conduction and so communicate in high frequencies. So our cleaver mammal ancestors developed a secret code to talk to one another free from detection from their predators.
So we know due to our evolutionary heritage very low-frequency sounds are read by the body as predatory. Now here is the really important take home…our modern workplaces are littered with low-frequency noses ranging from air conditioning, lighting, IT, and office machines. The reality is that even though our higher brain function knows we are in an office and not in a jungle or on the Serengeti it can’t override our survival mechanisms. Open plan office environments offer the double whammy to your nervous system by offering no control over your environment and with this our feeling of safety is compromised as literally our back isn’t covered.
So as we work out our lives in a soup of low-frequency predatory hums and a lack of safe walls to keep them out, our middle ear muscles begin to lose their neural tone and with it the ability to filer efficiently high & low-frequency sounds. We can become hypersensitive to the noise around us generally, things and people irritate us/get on our nerves and we lose the ability to pull human speech out of this soup. And all of this is happening on a level just below our conscious awareness. With our defense modes on this shut off our higher conscious brain areas adding to our stress levels, our ability to be resilient and ultimately our performance.
We have become the most successful species on this planet because of our amazing ability to work together so successfully. Emotional intelligence plays a big part as we need to be able to evaluate the emotions and intentions of others to know who is safe to work with and who isn’t. This is dependent upon the ability to detect relevant social cues from human speech, gestures, and facial expressions that make us feel safe and put us in a calm state. These skills are, in part, dependent on our ability to dampen irrelevant and often noisy background sounds so we can accurately detect and give socially appropriate cues and signals (e.g., facial expressions, head tilt, eye movements, vocalizations, and body posture), in other words, use our social engagement system effectively.
The Polyvagal Theory provides the foundation to build our resilience by giving us the science to build from. We can use the listening part of our social engagement systems as a portal to improve our overall state regulation. Dr. Porges has done just this with the Safe and Sound Protocol (SSP). The SSP is a five-day research-based intervention that involves listening to music that has been processed specifically to retune the nervous system to introduce an increased sense of safety and the ability to socially engage. It trains the middle ear muscles to once again dampen the low-frequency sounds while allowing the cues of safety our body needs to calm down, namely the frequencies of human speech. This has a knock-on effect of turning down out defense systems which percolates up to our higher brain regions allowing them to come back online.