Polyvagal Theory Part 1: The Evolution of Understanding

Polyvagal Theory has revolutionised our grasp of the human nervous system, challenging an outdated dualistic view. Before the formulation of polyvagal theory, the nervous system was thought of as a binary antagonistic system, with the stress response either on or off, stressed or not. It suggested that when faced with threats, the body would activate the autonomic nervous system, mobilise, then revert to homeostasis once the threat subsided.

Porges’ discovery revealed a nuanced reality: humans possess varied stress and nervous system activation states. He introduced a three-part hierarchical model, explaining the intricate role of the vagus nerve in the autonomic system’s communication and connectivity. This model emphasises the multifaceted nature of our stress response, enhancing our understanding of how the nervous system dynamically responds to diverse circumstances.

Before Polyvagal Theory 

Before the formulation of the polyvagal theory, the vagus nerve was identified as a significant player in controlling these heart rate changes. However, there was a persistent discrepancy – sometimes the nerve’s involvement didn’t align with observed heart rate shifts, creating a puzzle known as the “vagal paradox.” This inconsistency posed a challenge in understanding bodily responses and health implications. Researchers were grappling with this paradox, seeking an explanation that could unravel the mysteries of the nervous system’s intricate control over our body’s responses.

To make sense of this puzzle, Dr Porges formulated the polyvagal theory, suggesting that in our bodies, two systems related to the vagus nerve control our heart rate and other responses. This theory helps explain why our heart rate can change in different ways in different situations.

Early Concepts and Research

When it was introduced in 1994 by Dr. Stephen Porges, the polyvagal theory was a paradigm-shifting concept that shattered the binary myth.

Dr. Porges proposed a three-part hierarchical model, introducing the world to the varying states of stress and nervous system activation we undergo. Humans experience a spectrum of stress responses, each with its degree of activation within the autonomic nervous system.

Crucially, the theory highlighted the role of the vagus nerve – a key player in our autonomic system. The vagus nerve orchestrates a meticulous system of communication and connection, influencing how we respond to stressors and interact with our environment. The theory deepens our understanding of how our nervous system dynamically adapts to the diverse challenges life throws at us.

Dr. Stephen Porges conducted extensive research to formulate the polyvagal theory, delving into the complexities of the autonomic nervous system and the vagus nerve. His research involved a multidisciplinary approach, combining neuroscience, psychology, physiology, and behavioural biology insights. 

Neurophysiological Studies: Porges conducted numerous neurophysiological studies to understand the functions and responses of the vagus nerve. These studies measured physiological responses, such as heart rate variability, to various stimuli and stressors to gauge autonomic nervous system activity.

Clinical Observations and Case Studies: Porges studied clinical cases and observed individuals with different responses to stress and trauma. Through these real-life cases, he gained valuable insights into the patterns and dynamics of the autonomic nervous system, informing the development of the theory.

Polyvagal Theory Formulation: Porges integrated the findings from neurophysiological studies and clinical observations. This theory suggests that the vagus nerve has three distinct branches, each linked to different adaptive behavioural responses and emotional states.

Animal Studies: Porges also conducted research using animal models to better understand the evolutionary and comparative aspects of the autonomic nervous system. By studying the responses of mammals, he gained insights into the phylogenetic development of the vagus nerve and its role in the nervous system.

Application in Clinical Settings: Beyond research, Porges applied the insights from his studies practically in clinical settings. He collaborated with therapists and clinicians to explore the implications of the polyvagal theory for trauma treatment, attachment, social engagement, and overall mental health.

Through this research Porges developed this comprehensive framework to comprehend the autonomic nervous system’s intricate workings and its profound impact on human behaviour, emotions, and well-being.

The Beginnings Of A Theory: Core Concepts 

In order to understand our nervous system, the polyvagal theory brings forth three pivotal organisational principles.


The autonomic nervous system, responsible for our body’s automatic responses, operates in a hierarchical manner with three distinct reaction patterns that activate in a specific order. 

This hierarchy represents a structured sequence of physiological reactions based on the perceived level of threat or safety. 

The first response is the immobilisation or “freeze” response, followed by the fight or flight response, and finally, the social engagement response. The hierarchy reflects the evolutionary development of our body’s responses to stressors, illustrating the intricate ways our nervous system adapts to varying degrees of danger.


Neuroception is a concept that describes an unconscious, automatic form of processing and evaluating cues from our environment, particularly related to safety and danger. Unlike conscious perception, which involves deliberate and aware processing of stimuli, neuroception occurs without our conscious awareness. 

It involves rapid assessments of safety or threat, influencing our physiological and behavioural responses. For example, we might feel uneasy or tense in a certain environment without consciously understanding why. Neuroception is crucial for survival, as it helps prepare our body for action based on these unconscious evaluations.


Co-regulation is a fundamental principle highlighting the significance of feeling safe and secure within relationships, especially during early development and throughout our lives. It emphasises the mutual regulation of emotional states between individuals, often observed in healthy relationships. 

When we feel safe and supported by others, our autonomic nervous system can regulate stress and emotional responses more effectively. However, co-regulation can be challenging for individuals who have experienced trauma or lacked a sense of safety in their relationships. They may struggle to establish a sense of safety and struggle to regulate their emotional responses without external support, impacting their overall well-being and relationships. Healing and therapy often involve learning to co-regulate emotions and establish a sense of safety in relationships.

Current State of Understanding and New Insights

Incorporating these core concepts into our understanding of the nervous system reshapes how we view stress, behaviour, and overall well-being. The polyvagal theory continues to evolve, offering a profound lens through which we interpret the complexities of our body and mind. As research advances and applications broaden, we stand on the brink of unlocking even deeper insights into the mysteries of our nervous system and its influence on our lives.

Recent insights into polyvagal theory have highlighted its expanding influence in various domains. Clinically, therapists increasingly apply polyvagal principles in trauma-focused treatments, emphasising regulation, and safety. Understanding the mind-body link has become paramount, informing comprehensive approaches to mental health that encompass physiological and psychological dimensions.

In parenting and child development, polyvagal theory highlights the vital role of the parent-child relationship in shaping a child’s nervous system and emotional well-being. Exploring the social engagement system within the theory enriches comprehension of human interactions, enhancing social skills and relationship dynamics, and guiding stress management techniques, which foster resilience and emotional regulation. Its application extends to educational settings, promoting environments conducive to optimal learning and emotional balance.

To further explore how insights from polyvagal theory have informed theory and practice, look out for next month’s blog. 


  1. PORGES, S.W. (1995) ‘Orienting in a defensive world: Mammalian modifications of our evolutionary heritage. A Polyvagal Theory’, Psychophysiology. Received March 6, 1995; Accepted March 23, 1995, 32(4), pp. 301–318. Available at: https://doi.org/10.1111/j.1469-8986.1995.tb01213.x.
  2. Porges, S.W. (2003) ‘Social engagement and attachment: a phylogenetic perspective’, Annals of the New York Academy of Sciences, 1008(1), pp. 31–47. Available at: https://doi.org/10.1196/annals.1301.004.