Polyvagal Theory Part 2: Exploring Concepts and Theories

Polyvagal Theory has revolutionised our understanding of the human nervous system, challenging a binary view of stress responses. In the 1990s, Stephen Porges introduced a three-part model, highlighting the intricate role of the vagus nerve in the autonomic system, revealing diverse stress states. Polyvagal theory’s core concepts include hierarchy, neuroception, and co-regulation, influencing our understanding of stress responses and well-being. Its application extends to trauma treatment, child development, social dynamics, and education, shaping a holistic approach to mental health. A more in-depth exploration of the formulation and history of polyvagal theory can be found in last week’s blog: Polyvagal Theory Part 1: The Evolution of Understanding.

What is The Foundation of Polyvagal Theory?

Polyvagal theory explains our nervous system’s reactions to stimuli, encompassing the body’s assessment and response to safety and threat cues. Being active in all human experiences at a biological level offers a comprehensive framework for understanding human behaviour and why we act the way we do.

Understanding polyvagal theory requires some knowledge of the autonomic nervous system (ANS). Extending beyond the brain and spinal cord, the ANS intricately connects with the central nervous system. It regulates involuntary bodily functions, like heart rate and digestion. The ANS operates unconsciously, assessing safety and danger and triggering appropriate physiological responses through sympathetic and parasympathetic pathways. 

It plays a pivotal role in deciding whether we are in a state of safety or danger, guiding actions such as rest-and-digest or fight-or-flight responses – functioning like a personal surveillance system, scanning for signs of danger and adjusting our bodily functions accordingly.

Challenging traditional views, polyvagal theory revealed that the sympathetic and parasympathetic systems don’t simply operate reciprocally, with the sympathetic system activating the body’s “fight or flight” response causing adrenaline and other stress hormones to prepare the body for action, and the parasympathetic nervous system promoting a “rest and digest” state, calming the body, slowing heart rate, and aiding in digestion and relaxation after the stressor is removed.

Hierarchy of Response

The hierarchy of response in polyvagal theory means our autonomic nervous system activates different strategies based on perceived threat levels. Social engagement, the most evolved response, promotes safety and connection. When it fails, the system switches to fight-or-flight, preparing for confrontation or escape. If even that proves ineffective, the most primitive response takes over, leading to immobilisation and energy conservation in the face of extreme stress or perceived threat to life.2 A key part of understanding trauma responses and recovery is appreciating how the ANS can perceive certain sensory information to be dangerous or life threatening, even when it is not. The response to a threat is determined not by objective fact on whether a situation is dangerous or not, but instead by subjective experience of that threat alongside the stored information on past threatening situations.

Ventral Vagal Social Engagement

The ventral vagal complex is a crucial part of the ANS associated with feelings of safety, connection, and social engagement. When activated, it allows individuals to engage in meaningful and positive social interactions. This activation promotes a sense of well-being, emotional regulation, and empathy. The ventral vagal social engagement state allows us to establish connections, marked by openness, empathy, happiness, mindfulness, and inquisitiveness. Ventral vagal social engagement is a recent evolutionary development linked to the parasympathetic nervous system. It enhances bodily functions like digestion, immunity, circulation to extremities, social interactions, and relaxation while diminishing defensive reactions. It is therefore key in the process of returning to calmness, comfort and equilibrium after a stressful experience.1

Sympathetic Nervous System Activation

The sympathetic nervous system is one of the components of the autonomic nervous system and is primarily responsible for the “fight or flight” response when the body perceives a threat or stressor. The sympathetic nervous system, which emerged about 400 million years ago, predates the ventral vagal social engagement system by approximately 200 million years. It’s associated with a state of mobilisation, often termed “fight-or-flight,” where the body gears up to confront a perceived threat. Activation of the sympathetic nervous system triggers physiological changes including the release of stress hormones like adrenaline (epinephrine) and noradrenaline (norepinephrine) which prepare the body to either confront the threat or escape from it. During this phase, arousal intensifies, leading to increased blood pressure, heart rate, and circulation, but functions like digestion, immunity, and relational ability are reduced. These changes optimise physical performance and readiness for action, enabling individuals to respond to perceived danger swiftly and effectively.2 

To prevent sustained activation and potential harm, the body naturally shifts to dorsal vagal shutdown to regulate sympathetic activation and maintain overall well-being.

Dorsal Vagal Shutdown

The dorsal vagal complex is another component of the autonomic nervous system, which activates in response to extreme stress or life-threatening situations. When triggered, it leads to a “freeze” or “shutdown” response referred to as dorsal vagal shutdown. This response involves immobilisation and conservation of energy to endure the threat when fight-or-flight responses are ineffective or inadequate. It is a more ancient aspect of human functioning dating back about 500 million years, and is often described as an instinct to “play possum.” It leads to a freezing sensation, causing individuals to slow down, feel immobilised, lethargic, and trapped.1 In this state, various fundamental physiological functions decline, such as heart rate, blood pressure, temperature regulation, and immune response. Additionally, it affects social interactions, impacting eye contact, facial expressions, intonation, and sensitivity to human voices and social cues. It is linked to behaviours like dissociation, fainting, or feelings of helplessness, representing a last-resort survival strategy that helps individuals endure overwhelming situations by reducing metabolic activity and preserving vital resources.


Neuroception is a concept within polyvagal theory, developed by Dr. Stephen Porges. It refers to the subconscious and automatic process through which the nervous system evaluates the safety or threat level of the environment. Unlike perception, which involves conscious awareness, neuroception operates below the conscious level.

Neuroception allows the autonomic nervous system to assess environmental cues, like facial expressions, vocal tone, and subtle body language, to determine whether a situation is safe, dangerous, or potentially life-threatening.1 Depending on the nociceptive assessment, the autonomic nervous system regulates physiological and behavioural responses.

This process is vital for our survival and influences our emotional and physiological reactions to various situations and interactions. It helps us adapt to the environment by facilitating appropriate responses, whether that means feeling safe and relaxed or prepared for fight-or-flight, without requiring conscious thought or effort. While this is a survival strategy, it also means that the adaptive responses in activated states can alter a person’s perception of the world. This shift can cause non-painful sensory input to be interpreted as painful, particularly in cases of chronic pain related to trauma or stress.3 At a neurological level, it also means in cases of chronic stress or trauma, the brain becomes more attuned to potential threats, leading to the misinterpretation of neutral stimuli as dangerous. This persistent perception of a threatening world can be emotionally and physically draining, affecting various aspects of life, including relationships, work, education and daily activities. 

Healing Through Polyvagal Theory 

Healing from chronic sympathetic nervous system activation or dorsal vagal shutdown involves understanding and regulating the autonomic nervous system’s responses to stress and trauma. By recognizing how the body responds to perceived threats and learning to navigate its hierarchy of responses, individuals can promote emotional well-being and resilience. This understanding can lead to therapeutic interventions that emphasise safety and social engagement, helping individuals shift from states of anxiety, fear, or shutdown to a state of calm connection. Techniques like mindfulness, yoga, meditation, and trauma-informed therapies empower individuals to co-regulate their nervous systems, fostering healing from emotional wounds and trauma, and improving overall mental and physical health. Polyvagal Theory offers a framework for effective trauma recovery and emotional resilience.


  1.  Porges, S. W. (2011). The polyvagal theory: Neurophysiological foundations of emotions, attachment, communication, and self-regulation. W.W. Norton.
  2. Porges S. W. (2009). The polyvagal theory: new insights into adaptive reactions of the autonomic nervous system. Cleveland Clinic journal of medicine, 76 Suppl 2(Suppl 2), S86–S90. https://doi.org/10.3949/ccjm.76.s2.17
  3. Porges S. W & Dana D. (2018). Clinical Applications of the Polyvagal Theory: The Emergence of Polyvagal-Informed Therapies. New York: WW Norton.