Reading · Not (just) Another Neuroscience Blog

Before I go into discussing polyvagal theory (PVT), I want to give you a brief history of my relationship with it. Because PVT is essentially the reason I’m here, doing this work as a science communicator.
You see, I spent most of my scientific career studying the neuroscience of emotions and emotion regulation. I wrote my PhD on it. When I moved to a different country with my husband after my PhD I pivoted slightly into social and developmental psychology so started losing touch with neuroscience over the next nearly 3 years. And finally, after quitting my job to focus on my family for a while, I lost touch with science almost completely because I had no capacity to engage. However, when I started getting into the horse training world (of all things), I listened to a podcast and when someone mentioned neuroscience, nerves and nervous system states, my ears pricked and I was intrigued. This was familiar territory but I had never heard of this polyvagal theory. From afar, it made sense to me - needing to feel safe and seen, the importance of connection… I even looked into tapping, meditation, cold water exposure, all ways to “stimulate the vagus nerve” - according to a horse trainer… I almost got hooked, ok, I admit it. But then, luckily not that long after starting to be drawn in, something stopped me (I don’t remember what it was, I wish I did). I looked up the theory and read the info material on the website and started to see it more clearly - at the same time as being bombarded with “vagus nerve content” on social media which was infuriating. And that’s what tipped me over the edge of being motivated to start communicating science. So here we are.

The point is - I deeply understand the appeal of PVT, truly, I do. This is not to shame anyone. This is information, scientifically accurate to the best of my knowledge and with some scientific studies to support it. Please read to the end.

Here’s the biggest issue I have with PVT, on the basis of everything I have learnt in my 15+ years of experience as a researcher on psychological well-being including, specifically, cognitive and affective neuroscience, social psychology, developmental psychology. It is almost never possible, useful, or a good idea to reduce the complexity of the human experience to a small, discrete number of physiological elements. It’s something that is based on long outdated ideas of how the brain works and developed. I mean… if the constant comparison between reptiles and mammals doesn’t make you think of a certain Triune Brain idea (MacLean, 1977), you really haven’t been paying attention to developments in science (and if you still think you have a tiny dinosaur hiding under your cortex, ready to strike and control you when you least expect it, then you haven’t been following my Instagram closely enough). Look, human cognition and affect are really complex and complicated. And mostly, even though we love to focus on how the brain works, we won’t find the answers we hope for in brain imaging or even physiology research (we just don’t have the resolution or evidence base to do that). It’s impossible to break behaviour and experience down into small enough bits to unequivocally relate them to brain anatomy and function AND then recruit big enough samples to calculate probabilities.

There are people out there who have studied the vagus nerve in detail and who have devoted a lot of time and effort to collating the evidence that falsifies the assumptions underlying Porges’ PVT and show evidence that refutes Porges’ ideas about both the evolution and the functional anatomy of the vagus nerve (Grossman, 2023; Neuhuber & Berthoud, 2022). This includes both anatomical and functional aspects of how the vagus nerve works, evolved, and affects the outcome variable primarily used by Porges et al. to claim evidence supporting PVT. I don’t have the expertise or background to scrutinise this research but as someone trained extensively in the scientific method with experience in neuroscience and a neutral stance on vagus nerve anatomy, I have read Porges’ papers and the refutals and the responses to the refutals both by Porges himself and his supporters, and here’s what stood out to me:

Porges’ papers sound very convincing on the surface - he presents his ideas in the way that ideas tend to be presented in scientific papers (I’m referring to Porges, 2023). Supported by citations on various aspects of his hypotheses and in scientific sounding language. On closer inspection, however, most of his citations are from his own research groups. That’s a red flag. In addition, it seems that Porges only presents evidence that supports his ideas when one important aspect of writing a good paper is to at least consider alternative explanations to what has been observed. In contrast, the papers considering Porges’ ideas on the basis of decades of research on vagus nerve anatomy and function give a much more well-rounded picture of considering a range of evidence before drawing conclusions. That means, they give PVT the benefit of the doubt before showing evidence that contradicts its underlying assumptions, drawing a much more comprehensive image of vagus nerve evolution, structure and function.

In contrast, responding to this criticism, Porges and supporters (, instead of presenting evidence that unequivocally supports their ideas,) repeatedly state that PVT’s critics cannot have understood the theory correctly.
In addition, Porges has previously claimed that “The theory was not proposed to be either ›proven‹ or ›falsified‹” (Porges, 2021), and elsewhere it is stated that “it’s just a polyvagal theory, not a polyvagal truth” - if we are aware of the meaning of the word “theory” in the scientific sense as representing a summary of the best evidence we have on a certain topic, then this, at the very least, should raise suspicion.

Then there is the concept of “Neuroception”, a term that was coined by Porges - a fact that makes it seem as though no one else has considered the idea that a lot of our information processing never reaches the threshold of conscious awareness. When, in fact, the way our brains process information without us knowing has been studied for a long time (Bargh et al., 2012; Williams et al., 2009). For example, there are studies on subliminal priming where images are shown so briefly that we don’t consciously see them but they still affect our choices (Pantazatos et al., 2012; Pichon et al., 2016).Supporters would call this support for PVT but is it really? Considering neuroception as part of PVT you’d be forgiven for thinking the vagus nerve was somehow involved in it, since the whole basis of the theory is the assumed functional division of the nerve. Although Porges has revoked the idea of a “smart vagus” (according to his responses to criticism), the fact that there seems to be no further education on how subconscious processing actually works and what’s involved, leaves room for assuming that the “ANS” somehow possesses access to information separate from what we can see hear, smell, taste… you get my drift. And looking at the way that PVT is often communicated on social media, this room is used - spiritual ideologies are common in these spaces. Jung’s collective unconscious, energies, telepathy… And it’s all fine and good to believe in this stuff - but to call it scientific is just so misleading.

In addition, the idea of the autonomic nervous system “scanning for clues of safety and danger”, once again, is reminiscent of the idea of “older” and “newer” brain systems, “reptile brains”... we’ve been there, talked about that.

Finally, there’s the principle of co-regulation, the idea that mammals read clues about each other’s emotional state from facial expressions, tone of voice and body language and that affects how we engage with each other. While this is, generally speaking, supported by evidence (although not as straightforward as being automatic and accurate, see Barrett et al., 2019), Porges goes on to say that this is dependent on the ventral vagal system, which both helps us to regulate and send these signals out to others. This is not supported by evidence.

This is where I tell you why this essay has taken me a ridiculously long time to write. We’ve considered the underlying assumptions about anatomy and function of the VN, neuroception and the overall scientific-ness of the theory. So now we should get into the practical suggestions, the applications. And this is where I’ve been struggling to make this coherent. The jump from a theory of a functionally divided vagus nerve to nervous system dysregulation and universal trauma is a bit too large for me.

Let’s start here: The free information materials on the polyvagal institute’s website suggest that your autonomic nervous system can become “faulty” (not paraphrasing here, this is a quote) due to trauma or chronic stress and that this affects both neuroception as well as the physiological processes in your body as a response to threat. And it is assumed to affect co-regulation, i.e. the ability to regulate in response to others’ clues of safety and connection. According to PVT, when our nervous system is faulty, we might misinterpret signals both in the environment and from other people. So the consequence is that we need to fix our nervous systems with polyvagal interventions to be able to connect and read safety clues correctly. Ok. There's a lot to talk about here. Firstly, of course, individuals with mental health issues might have trouble interpreting their environment, other people, and their own physiological experiences in helpful and healthy ways. This is well known and not an idea unique to PVT. It is also extremely unlikely to be due to a “faulty nervous system”, or even a “faulty” vagus nerve, as you’d be forgiven to assume PVT suggests. The vagus nerve is like an electrical wire, transmitting signals between the brain and several organs. The information comes from the brain, is transmitted and looped back. Sure, nerve disorders might exist, but there is no evidence that they underlie a significant proportion of mental health diagnoses. Instead, we know that most mental health issues are multi-factorial and their development is influenced by biological, psychological, and social factors (Garcia-Toro & Aguirre, 2007; Sampogna et al., 2024). That doesn’t rule out an involvement of the vagus nerve, but as stated previously, there is currently no evidence for it either. And referring to the science principle of Occam’s razor (Blumer et al., 1987) - we should accept the simpler of two alternative explanations to a problem - it does feel as though the whole vagus nerve discussion is unnecessary excess.

And then there is the the way that this theory is communicated. I watched the official information video and it really made me scratch my head. It paints a picture of us as victims of our faulty and completely uncontrollable autonomic nervous system that either helps or hinders functional social interaction and experience. It suggests an idea of universal trauma as indexed by chronic stress and autoimmune disease and lists a number of symptoms of “nervous system dysregulation” that anyone would be able to find themselves in. It suggests that this unspecified “nervous system dysregulation” is essentially the “root cause” of all of the world’s problems - so PVT is the key to “healing the world”. Consequently, this also suggests that every single one of us probably is dysregulated and should apply polyvagal principles to their healing.

And this messaging is also reflected in a lot of polyvagal-adjacent social media posts - often descriptions of very general “symptoms” of being in “survival mode” that are often a normal part of the human experience, designed to catch the unsuspecting social media user and draw them into the content - hoping for healing, and paying for the pleasure. It’s understandable - as mentioned above, I myself was drawn in for a minute or two, despite the extensive education I have in the neuroscience of emotion and mental health.

“But it helps people” - maybe. Maybe it helps people by providing non-judgemental space. Maybe it helps people by relieving them of feelings of shame about how they feel, by relieving them of some of the responsibility for their feelings with scientific sounding explanations of physiology, no matter their accuracy. Maybe it helps people who didn’t even know they needed help until they stumbled upon PVT on social media and were told that they did. Maybe it also doesn’t help a lot of people that we never hear from. Maybe it helps people because a lot of the interventions that are suggested have been shown to be effective for some people because they pull us into the present - and being present stops us from ruminating which, in turn, has been shown to be associated with reduced symptoms of anxiety and depression (Nolen-Hoeksema, 2000; Nolen-Hoeksema et al., 2008). But probably not because they activate the vagus nerve. I just don’t think it’s ever a good idea to mislead people. We’ve got great science on what affect and emotions are, how they are constructed, how they influence how we make sense of each other and the world (Barrett, 2017). I’d love to see that spread the same way that polyvagal theory is spread.

And then there’s the societal issue. The messaging, placing the blame on our faulty nervous systems. It’s not *you* that’s faulty, it’s your nervous system. Blame your nervous system for all your problems and heal it. Find the trauma that you must have had because you seem dysregulated to me, even if you say you’re quite happy, actually. Reverse inference - inferring trauma from “dysregulation”, rather than reporting trauma and working on the resulting changes in beliefs, attitudes and physiology. In addition, if everyone has experienced trauma - then how do we make sense of particular diagnoses such as PTSD? And what if someone with a serious mental health disorder finds PVT before they can access a diagnosis or while they are waiting to see a therapist? What if it doesn’t work for them and now they are really convinced that something is seriously wrong with them? Or what if they’re reluctant to try an evidence-based intervention for their mental health diagnosis because they’ve been misled and therefore never get effective treatment for their condition?

Although it was possibly once based on a scientific idea, PVT’s messaging has, over time, become very much like most wellness social media content - introducing a set of non-specific, varied symptoms, and a “root cause” - along with the miracle solution to “fix you” that your doctor doesn’t tell you about. And the latter illustrates another issue I see with PVT - promoters of PVT based therapies often discourage people from seeking evidence-based help in the form of talking therapy and this is highly problematic! People have a right to know about and access evidence-based treatments (i.e. treatments that have been shown to be effective through scientific studies including randomised controlled trials) - something that is distinctly lacking for PVT. PVT’s messaging pathologises healthy human experiences, reverse engineers trauma, and puts people with serious mental health disorders at risk. It also places the entire responsibility for our mental health on the individual, ignoring or at least downplaying societal factors that have a very real impact (I believe there is a statement in the promotional video along the lines of “modern life is too stressful for us” - but the consequence was still to “heal your nervous system”).

PVT is self-help, wellness disguised as science and as that, it’s extremely misleading. It is at odds with the current best scientific knowledge of how the mind and brain work, or how mental illness manifests. I won’t tell you what to do - if PVT is an anchor for you, I’m not here to discount your experience with it. But take this as an invitation from a scientist to ponder that the concept is neither particularly scientific, nor is it unique. And maybe, if you talk to others about what you do for your own mental health, just keep that in mind.

References:

Bargh, J. A., Schwader, K. L., Hailey, S. E., Dyer, R. L., & Boothby, E. J. (2012). Automaticity in social-cognitive processes. Trends in Cognitive Sciences, 16(12), 593–605. https://doi.org/10.1016/j.tics.2012.10.002

Barrett, L. F. (2017). How emotions are made: The secret life of the brain (pp. xv, 425). Houghton Mifflin Harcourt.

Barrett, L. F., Adolphs, R., Marsella, S., Martinez, A. M., & Pollak, S. D. (2019). Emotional Expressions Reconsidered: Challenges to Inferring Emotion From Human Facial Movements. Psychological Science in the Public Interest, 20(1), 1–68. https://doi.org/10.1177/1529100619832930

Blumer, A., Ehrenfeucht, A., Haussler, D., & Warmuth, M. K. (1987). Occam’s Razor. Information Processing Letters, 24(6), 377–380. https://doi.org/10.1016/0020-0190(87)90114-1

Garcia-Toro, M., & Aguirre, I. (2007). Biopsychosocial model in Depression revisited. Medical Hypotheses, 68(3), 683–691. https://doi.org/10.1016/j.mehy.2006.02.049

Grossman, P. (2023). Fundamental challenges and likely refutations of the five basic premises of the polyvagal theory. Biological Psychology, 180, 108589. https://doi.org/10.1016/j.biopsycho.2023.108589

MacLean, P. D. (1977). The Triune Brain in Conflict. Psychotherapy and Psychosomatics, 28(1/4), 207–220.

Neuhuber, W. L., & Berthoud, H.-R. (2022). Functional anatomy of the vagus system: How does the polyvagal theory comply? Biological Psychology, 174, 108425. https://doi.org/10.1016/j.biopsycho.2022.108425

Nolen-Hoeksema, S. (2000). The role of rumination in depressive disorders and mixed anxiety/depressive symptoms. Journal of Abnormal Psychology, 109(3), 504–511.

Nolen-Hoeksema, S., Wisco, B. E., & Lyubomirsky, S. (2008). Rethinking Rumination. Perspectives on Psychological Science, 3(5), 400–424. https://doi.org/10.1111/j.1745-6924.2008.00088.x

Pantazatos, S. P., Talati, A., Pavlidis, P., & Hirsch, J. (2012). Cortical functional connectivity decodes subconscious, task-irrelevant threat-related emotion processing. NeuroImage, 61(4), 1355–1363. https://doi.org/10.1016/j.neuroimage.2012.03.051