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Understanding the Window of Tolerance and Polyvagal Theory, Part 2

Polyvagal Theory: How the Nervous System Detects Safety and Threat

This is Part 2 of our three part series about the Window of Tolerance and Polyvagal Theory. Read Part 1 here that specifically explores The Window of Tolerance.

Ready for Part 3? –>Connecting the Dots: Applying the Window of Tolerance and Polyvagal Theory in Daily Life

While the Window of Tolerance describes where we are in terms of regulation, Polyvagal Theory, developed by neuroscientist Dr. Stephen Porges, explains how and why the nervous system shifts between states in response to cues of safety and danger. The ANS controls many automatic functions—like heart rate, breathing, digestion, and arousal—without conscious effort. Polyvagal Theory focuses on how the autonomic nervous system (ANS) continuously scans for cues of safety and danger, often outside conscious awareness, to decide whether it is safe to connect, fight/flight, or withdraw. Deb Dana, LCSW, has translated this theory into practical strategies for therapy settings and to help people understand how the nervous system shapes behavior and emotional responses in their daily lives.

The Three Primary Nervous System States

According to Polyvagal Theory, our nervous system organizes responses into distinct states based on perceived safety, with three primary pathways of the autonomic nervous system (ANS) each producing characteristic patterns of physiological and behavioral responses.

1. Ventral Vagal State (Safety and Connection)

When the nervous system perceives safety, it activates the ventral vagal system. In this state, people tend to feel:

  • Calm and present
  • Emotionally regulated
  • Able to connect, communicate, and engage socially
  • Flexible in problem-solving and decision-making

This is the state most closely aligned with the Window of Tolerance, where emotions can be felt and managed without becoming overwhelming.

2. Sympathetic State (Mobilization: Fight or Flight)

When the nervous system detects threat or stress, it may shift into sympathetic activation, preparing the body for action. This is often experienced as:

  • Urgency, anxiety, or panic
  • Irritability or anger
  • Racing thoughts
  • Physical tension or restlessness
  • Hypervigilance

This state is not inherently harmful — it is a protective survival response. Problems arise when the nervous system becomes stuck in sympathetic activation or when the response is triggered by perceived rather than actual danger.

3. Dorsal Vagal State (Immobilization: Shutdown, Freeze, or Collapse)

If a threat feels overwhelming or inescapable, the nervous system may shift into dorsal vagal activation, characterized by immobilization (often referred to as freeze). This can look like:

  • Emotional numbness or dissociation
  • Fatigue or low energy
  • Withdrawal from others
  • A sense of hopelessness or disconnection

The related response, sometimes called fawn (people-pleasing or appeasing behaviors), is understood as a blended survival strategy that involves sympathetic and dorsal vagal activity, especially in relational contexts (Martin, 2025).

From a polyvagal perspective, these states and responses are not choices or character flaws—they are adaptive and automatic reactions shaped by trauma, chronic stress, and early attachment experiences and context (Mansoor, 2025), and are the nervous system’s effort to maintain safety.

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