In a meeting growing steadily hotter, a colleague made a pointed remark about Mint in front of everyone. Once, she would have answered back. Today, what came instead was emptiness.

It was as though the line of communication in her head had simply been cut. Her whole body went numb, no words would come, and she sat still until the meeting ended. Only once she was home did she think of everything she should have said — and then grew angry with herself all over again. “Why was I mute? Why could I not defend myself at all?”

What Mint experienced corresponds to polyvagal theory, which describes modes of response in the autonomic nervous system.

But let us set the frame clearly from the outset. The autonomic nervous system, which governs heart rate, breathing and the response to stress, is a matter of well-established physiology. Polyvagal theory is a particular theory proposing a way of explaining how that system works. It is enormously popular within the therapeutic field, while several of its central claims remain scientifically contested. We will keep those two things clearly apart throughout.

What polyvagal theory proposes

Polyvagal theory was proposed by the researcher Stephen Porges in the 1990s. At its heart is the proposition that our autonomic nervous system — comprising the sympathetic and parasympathetic systems, and particularly as it concerns the vagus nerve — does not have merely an “accelerator” and a “brake”, as was traditionally understood, but responses more complex than that, closely bound to the sense of safety and to social connection.

The theory became highly popular in therapeutic work with stress and psychological wounds, because it offered a frame for understanding an experience many people have felt without being able to describe — particularly the state of freezing, or going numb, as Mint did in that meeting, which fight-or-flight alone does not fully account for. That said, popularity within the therapeutic field and the accuracy of the physiological mechanism a theory proposes are two different matters, and we will return to that.

How polyvagal theory describes fight, flight, freeze and safety

Within the frame of polyvagal theory, the experience of the nervous system can be described simply as three broad patterns, according to whether safety or threat is perceived. The body does not work in separate compartments — several systems may be operating in combination at the same time.

The first pattern is a state of calm, ready for connection with others, which the theory links to what it calls the social engagement system and the ventral vagal branch. It is the state that allows us to talk with people, be sociable, and feel at ease when the nervous system perceives safety. The second is fight or flight, linked to the sympathetic nervous system, arising when the system perceives an approaching threat, so the body accelerates to meet it — heart faster, muscles tight. And the third is a response of immobilization or shutdown, which the theory links to the dorsal vagal branch and proposes arises when the system judges a threat to be severe or inescapable, so the body enters a state of numbness, stillness, or abrupt disconnection. The terms freeze, tonic immobility, collapse and shutdown, though, do not always refer to the same physiological state, and should not be used interchangeably. Collapsing them all into a single kind of shutdown is one of the points on which simplified uses of polyvagal theory are criticized.

These three patterns — calm, fight or flight, and immobilization or shutdown — are something a great many people experience, and the idea of responding by fighting, fleeing or freezing is already broadly accepted in stress research. What is specific to polyvagal theory, and what is disputed, is its account of how these modes connect to particular branches of the vagus nerve, and the evolutionary story behind it. We come to that next.

An analogy: a security system with three modes

Think of the polyvagal system as a building’s security system with three modes.

In its ordinary mode the doors are open, people come and go, conversation flows freely. This is the state in which we feel safe and ready to connect with others. When the system detects a signal of danger, it switches to alarm mode: everything accelerates, preparing to meet the threat or to flee, like an alarm sounding through the building. And if the threat is too great to fight or escape, the system may enter lockdown, shutting everything down to keep the people inside safe — the building gone dark and entirely silent. Which is the state of freezing, of going still.

The important thing about this picture is that none of the three modes is a deliberate choice, and none of them means we are weak. They are automatic, the body trying to protect us according to its own assessment of the situation. Mint entering lockdown was not cowardice. It was a response that arrived quickly and automatically, before she had time to choose an answer consciously.

What remains disputed about polyvagal theory

This is the most important part of the article, and the part general accounts usually omit. Many people wonder whether polyvagal theory is reliable. The straightforward answer is that although it is widely adopted in therapeutic practice, several of its central claims are questioned and substantively disputed among physiologists and neuroscientists.

The most criticized element is the evolutionary account. The theory proposes that the myelinated branch of the vagus nerve, linked to calm and social engagement, is found only in mammals. Many researchers point out that comparative biological data do not support that claim as the theory asserts, since similar structures are found in other groups of animals. There are also disputes about linking certain physiological measures to the theory’s predictions, where the evidence is not as firm as it ought to be.

Another significant criticism is that the diagram pairing “ventral vagal equals safety”, “sympathetic equals fight or flight” and “dorsal vagal equals shutdown” is elegant and easy to communicate, but may be simpler than the actual physiology — because the response to threat arises from the coordination of many systems: circuits in the brain, the brainstem, hormones, the cardiac system and breathing. It is not governed by one branch of the vagus nerve alone. A great deal of the criticism is therefore directed at attributing more explanatory power to the vagal branches than the data support. This includes terms the theory coined, such as neuroception — the nervous system detecting safety or threat without conscious awareness — which is the theory’s own vocabulary, not a standard term used with the same meaning across every framework in neuroscience.

So what can we genuinely take from this?

The principle is that both the felt sense of safety and the actual conditions of safety around us influence how the body responds — and that we may have some measure of influence over our own autonomic nervous system. Breathing deeply and slowly, for instance, without forcing the breath uncomfortably deep, has evidence of affecting the workings of the cardiac and autonomic systems, and helps many people feel calmer. Being in environments and relationships that feel safe also helps the nervous system settle. And understanding that freezing is not our fault helps reduce the self-blame that usually makes everything worse.

If freezing, numbness, or a severe stress response begins to affect daily life or relationships persistently — particularly where it connects to painful experience in the past — speaking with a mental-health professional who understands psychological wounds will address it more precisely than carrying it alone. And if distress ever becomes more than you can bear, Thailand’s mental health hotline, 1323, is staffed by people who will listen, twenty-four hours a day.

At NBRH we work on the principle of Neuro-Behavioral Repatterning & Hypnotherapy: adjusting the nervous system’s patterns of response, and behavior, systematically — with the felt sense of safety treated as the foundation. Because lasting change does not come from ordering yourself to stop being afraid, or to stop going still. It comes from gradually building a sense of safety in the nervous system, until it no longer needs to jump into a protective mode so quickly, and has more flexible options for responding. That is what lasting change means.

If you would like the wider principle behind that kind of change, “What Neuroplasticity Is” explains how the nervous system learns a new response.

What Polyvagal Theory Is: Understanding the Body’s Modes of Fight, Flight and Freeze