Polyvagal Theory: A Very Simple Introduction

Many approaches in psychology focus on thoughts. 

However, our thinking can only ever be a product of what’s happening at a deeper, biological level – the level of the nervous system.

In fact, the health of our nervous system is perhaps the most important determinant of our mental and physical wellbeing. 

It influences not only what we think, but also how we feel, and how we act in day-to-day life.

Think of an iceberg.

Polyvagal Theory Simplified
Photo by Danting Zhu on Unsplash

Our thoughts are the ‘tip’ that’s visible above the surface. 

The activity of our nervous system is the 87% (or more) of the iceberg that scientists estimate is submerged under water.

So if we want to improve our quality of life, we need to understand what’s happening ‘beneath the surface’, and also be able to influence it. 

One of the most influential approaches for achieving this is Polyvagal Theory (PVT), put forward by Dr Stephen Porges in 1994 – a Professor of Psychiatry at the University of North Carolina, who has published more than 400 peer-reviewed articles. 

In simple terms, PVT suggests the state of our nervous system determines how safe and connected we feel in day-to-day life. Some states lead to disconnection, withdrawal and self protection, while others promote social engagement, exploration, and curiosity. 

Part one of this post will provide an accessible introduction to the theory.  

The second will explore how polyvagal insights can be leveraged to experience more wellbeing, safety, and connection in day-to-day life. 

The Vagus Nerve & Polyvagal Theory

Polyvagal Theory Simplified
Photo by Arno Senoner on Unsplash

Your nervous system is like a personal surveillance system, always asking the question: 

“Am I safe?”

It evolved to protect us from danger, and to keep us safe and connected in our evolutionary past. 

To do this, it engages in a kind of ‘listening’ beneath the level of conscious awareness, both to what is happening in the external environment, and also to what’s going on inside our bodies.

Broadly speaking, the nervous system is made up of two ‘branches’; the parasympathetic and the sympathetic. 

The sympathetic branch is located in the spinal cord. It’s designed to mobilise us for action, and respond to cues of threat in the environment. 

It’s what gives us the ‘fight or flight’ response. 

When active, it floods our system with adrenaline to mobilise us to deal with the perceived danger.

The parasympathetic branch is found in the cranial nerves. 

We have 12 pairs of cranial nerves, each of which emerge directly from the brain. 

The longest of these is the ‘vagus’. 

‘Vagus’ which comes from the Latin: ‘wandering’, is aptly named, as it travels all throughout the body in two directions. 

Polyvagal Theory Simplified
Photo by Krisjanis Mezulis on Unsplash

It moves downward from the brain through the lungs, heart, stomach, and diaphragm, and upward from the diaphragm to connect with the nerve fibres in the neck, throat, ears, and eyes.  

This is the central component of our parasympathetic nervous system. 

It’s divided into two separate pathways:

1.) The dorsal vagus

2.) The ventral vagus

Understanding this division is at the heart of polyvagal theory.

The 3 Organising Principles of Polyvagal Theory

Polyvagal theory is built upon three simple principles: 

1.) Hierarchy

2.) Neuroception

3.) Co-regulation. 

In this section, we’ll briefly introduce each one, and how understanding it can improve your quality of life. 


The nervous system responds to environmental signals through three pathways, and it does so in the order that these pathways evolved. 

Although all three evolved to help us survive, they do so in very different ways. 

The Dorsal Vagal Pathway

The oldest pathway, from approx. 500 million years ago, is the dorsal vagus, which responds by immobilisation

It gets us to withdraw, dissociate and disconnect when we are feeling unsafe or unworthy. 

If you think of your nervous system like a home, the dorsal vagal pathway is like a dark basement that you retreat into, and hide when the outside world feels unsafe.

Dorsal Vagal - Polyvagal Theory
Photo by Daniel Lincoln on Unsplash

It responds to danger by putting us into an immobilised state, shutting down bodily systems and preserving energy. 

This is the pathway that’s active when animals ‘play dead’ to protect themselves from predators. 

Dorsal Vagal - Polyvagal Theory
Image credit: Wiktionary.com

When we are in a dorsal vagal state, less blood and oxygen flows to the brain, often resulting in dissociation and a decline in cognitive abilities. 

Here, we feel numb, frozen, and absent. 

The dorsal vagal pathway ‘comes online’ when we are in a situation of extreme danger that we can’t escape from. 

And because we can’t escape physically, we attempt to escape mentally. 

We shut down and dissociate from the experience in order to survive. This explains why many trauma survivors experience dissociation in the midst of a traumatic experience. 

The Sympathetic Pathway

Next to evolve, around 400 million years ago, was the sympathetic pathway, which equipped us with the ‘fight or flight’ response.

Returning to our metaphor of the home, the sympathetic pathway is like the alarm security system. 

Sympathetic - Polyvagal Theory
Image credit – nottinghamshire.police.uk

It’s there to put us into ‘fight or flight’ mode, which it does by flooding our system with adrenaline when we sense danger. 

This helps us to either engage with perceived threats or avoid them.

In our evolutionary past, it helped us to sprint away from predators or climb up a tree to avoid being eaten. 

However, back then, it would’ve only come ‘online’ occasionally in response to major threats, and been followed by a period of relaxation, soothing, and recovery. 

In modern life, it can be difficult to disengage from the sympathetic pathway; whether it’s the constant flood of doom news about wars and pandemics, an insecure working situation, or an overly competitive, individualistic culture that places more value on the achievement of extrinsic rewards (e.g. money & status) over more intrinsic values (e.g. connection, creativity and community). 

Being in a sympathetic state also causes us to misread social cues. 

We see neutral faces as angry, and process most incoming information through the filter of “is this a threat”? 

The Ventral Vagal Pathway

Last to evolve, around 200 million years ago, was the ventral vagal pathway. 

Often referred to as the ‘social’ vagus, it becomes active when we feel safe, connected and socially engaged with others. 

Again, if we think of our nervous system like a house, this pathway is like the warm, social living room where the family come together in the evening, light a fire, play games together, and connect with each other on an emotional level. 

Ventral Vagal - Polyvagal Theory
Image credit: videohive.net

Spending time in a ventral vagal state is vital for mental and physical wellbeing, and is associated with recovery, curiosity, creativity, exploring new possibilities and a willingness to experiment.

Here, we feel calm, hopeful and open to change. 

Navigating the hierarchy with flexibility

As the name ‘hierarchy’ suggests, there is a kind of ‘ladder’ system at work here.

Polyvagal Theory Explained
Image credit – Deb Dana & Debbie Spengler.

At the bottom is dorsal vagal, in the middle we find sympathetic, and the top is ventral vagal. 

In the same way that we can’t just ‘jump’ up a ladder, we also can’t bypass states. 

This means if you are in a dorsal vagal state (immobilised and dissociated), you can’t immediately go into ventral vagal, without passing through sympathetic first.

You have to travel up through the ladder, one rung at a time. 

If our aim is to improve wellbeing, we need to be able to move between each of these states with flexibility, and not get stuck in any particular one. 

Now that we have an understanding of the three states, let’s look at the mechanism the nervous system uses to determine which one to ‘activate’ at any moment in time.



Neuroception - Polyvagal Theory
Image credit – Dreamstime.com

Neuroception is best thought of as a kind of ‘listening’ the nervous system engages in beneath the level of conscious awareness. 

It happens in the background; scanning the environment for cues of safety and danger. 

Depending on how our nervous system ‘interprets’ a situation determines which pathway (dorsal vagal, sympathetic or ventral vagal) comes online.

Trauma-informed mental health professionals understand that how events are perceived subjectively, is more important than any kind of objective reality. This means that two individuals could experience the exact same event, and one could come away with a deep traumatic scar, while the other might actually grow from the experience. 

In other words, our subjective experience of an event creates posttraumatic consequences; not the event itself. 

In Polyvagal theory, neuroception comes before perception.

This means that polyvagal-informed therapists give less weight to the client’s cognitive interpretation of the experience (the story), and instead focus on the nervous system’s response (the state).

This is grounded in the premise that ‘story follows state’. 

We know that 80% of the vagus’ nerve fibres send sensory information up from the body to the brain, while only 20% send information downwards from the brain to the body – meaning our thoughts are a product of the activity of the nervous system. 

Knowing this, it makes more sense to start by aiming to understand the autonomic response and building from there. 

For this reason, the polyvagal informed therapist asks: “What happened?”, not to learn about the details of an experience, but instead to understand how the client’s nervous system responded in the situation.

Neuroception isn’t always accurate

Neuroception - Polyvagal Theory
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Clients who come to therapy – particularly trauma survivors, often have a misattuned neuroception. 

Past experiences can cause their nervous system to misinterpret safe environments as dangerous, and render them ineffective at responding appropriately to danger. 

And this often causes significant problems in daily living; both for themselves and others.

Another key goal of polyvagal-informed therapy then, is to help clients develop a neuroception that more accurately reflects reality. 

One of the primary ways this is achieved is through “Co-Regulation” – the third organising principle of Polyvagal Theory.


Co-Regulation - Polyvagal Theory
Photo by Korney Violin on Unsplash

In simple terms, this is the process of sending and receiving signals of safety with others. 

It’s what happens when two nervous systems connect. 

Feelings of safety, warmth and connection are created, and both individuals leave the interaction feeling psychologically nourished and regulated. 

In our evolutionary past, social connection was essential for survival. 

Without the safety of our tribe, we were an easy meal for the many predators roaming the savannah. Therefore, in polyvagal theory, co-regulation is seen as a biological need that is as important for mental health, as food and water are for physical health.

In fact, going without it is as harmful as smoking 15 cigarettes a day

Many clients who come to therapy are often missing supportive co-regulating relationships in their lives. This puts them into a continuous neuroception of danger, causing them to spend a disproportionate amount of time in sympathetic (fight or flight) and dorsal vagal (withdrawal) states. 

Therefore, one of the first aims of a polyvagal-informed therapist is to effectively co-regulate with their client, and provide a deep, secure connection that they might not find elsewhere. 

The therapeutic relationship then provides a new ‘model’ of safe relating that the client can apply in their other relationships.

Which brings us to an interesting point..

Our nervous systems have plasticity

This means that although the self-protective strategies of our nervous system may have become habitual, they are not set in stone.

With the right approach, they can be ‘rewired’ for greater connection and safety. 

And even if it’s currently dormant, our ventral vagal system is always there, waiting to come ‘online’.


Follow Up Resources

The main resource used in researching this post was The Polyvagal Theory in Therapy by Deb Dana. 

Deb is a clinician, consultant, and author who specialises in working with complex trauma. 

Along with Dr Porges, she has been one of the leading voices in making Polyvagal insights more accessible both to therapists and the general public through her books and teaching. 

You can learn more about Deb’s work here, and see further resources below: 

 Befriending Your Nervous System (audiobook) 

 Anchored: How to Befriend Your Nervous System Using Polyvagal Theory

 Polyvagal Exercises for Safety and Connection: 50 Client-Centred Practices 

 Courses & Training

 Polyvagal Safety – Dr Stephen Porges

Niall McKeever

Niall McKeever

Writer and Founder of The Weekend University. Passionate about making great ideas more accessible.

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