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The Enigma of Freeze: Unraveling its Many Faces within the Fight-Flight-Freeze Phenomenon

a person's hands against a unclear glass

The phrase "fight-flight-freeze" has become part of the mainstream vocabulary when talking about Post Traumatic Stress Disorder (PTSD) or psychological trauma. Magazine articles, books, podcasts, and webinars have explored the "fight-flight" part so exhaustively for the past 5-10 years that most people now understand that concept pretty well: we know that fight-or-flight is a reaction of our body (the autonomic branch of the nervous system actually) to encountering the fear of danger our primitive ancestors felt. 

Fight-or-flight is immediate and aims to protect us, but it most often acts in extreme ways, out of proportion to the real level of danger. The term has been used to explain traumatization so much that many people may think they are the same; trauma indeed could be a consequence of the activation of this fight-or-flight mechanism when it fails to protect “the prey,” but if you experience fight-flight, it doesn’t mean you are necessarily traumatized. It means that your fear response got activated to protect you.

The "freeze" (sometimes called “freeze-faint”) part was added later to expand on the survival model that explains the development of PTSD, and encompasses everything else that happens while at risk. This is actually the part of the survival mechanism that plays a bigger role in traumatization and therefore, it’s worth understanding it better to know when, why and how this occurs. 

Even in trauma books and professional journal articles, we can find many different explanations and points of view about the "freeze" reaction, with descriptions of different concepts that are often contradictory and confusing. Here I intend to be more detail oriented trying to understand “freeze,” by separating the different concepts that have been described as such, and to make the sequence of the fear response when people become “frozen” easier to follow. 

Brain Considerations

The triune brain model and theory (MacLean, 2960) separates functioning of the brain on three different levels (primitive, paleomammalian, & neomammalian) as it has evolved throughout human history. Regardless of whether the brain has evolved exactly like that or not, this model offers a useful framework to understand how traumatization occurs. Please keep in mind the following assumptions:

  • the brain is a very sophisticated "apparatus" programmed to perform a series of tasks in the most effective possible way, optimizing the use of energy and resources it counts on. Upon increasing levels of threat, the brain reacts automatically with a series of steps that are not reasoned or chosen;

  • the “primitive” brain doesn’t understand well-being, happiness, etc. It mainly focuses on performance, optimization and efficiency, and its ultimate goal is survival (or to keep life going) by controlling the body's vital functions;   

a lion attacking a zebra
Primitive instincts
  • the emotional factor of the mammalian brain adds energy consumption to the already difficult task of survival. Instead of only trying to avoid death, the limbic (or emotional brain) also tries to gain safety, maintain family and affiliation, avoid isolation, etc.; 

  • the neocortex, the more evolved part of our brain — the part that is so amazingly powerful and allows for the human experience— makes the survival process more complex due to the need to attach and connect, to believe and have, to understand and care, etc. But the cortex, especially its frontal part, adds also the positive effect of evaluating and stopping irrational responses, and resources from strategies like hope and faith; all actions and reactions can become habits, and therefore automatic. If they are repeated frequently, the brain will assume it needs to learn them, and these habits will override the capacity to discriminate on whether they are useful or detrimental for our mental or physical health;

  • the strategies of survival are those that create a series of adjustments in our system by allocating  energy for the struggle, removing it from the organs/functions that will not be used during the survival tasks. These strategies follow a sequence to move in the direction of survival; every time the allocation of the energy seems ineffective, the system keeps making adjustments with new ways to re-allocate functionality until it feels certain that the body keeps alive no matter how;

  • these strategies (fear responses) follow a flow because there is a cascade of activation of hormones and neural activity every time one strategy for survival is considered ineffective. If a strategy succeeds, the body will go to a baseline level as soon as possible to continue with normal functioning and balance (homeostasis). But if a strategy fails, the Autonomic Nervous System (ANS) will change the plan and will activate a different set of hormones/organs/functions to achieve its goal of continual operating. How this “failure” gets evaluated by the ANS is a mystery, but in the case of humans, it’s highly related to thoughts and emotions, and therefore to the concept of resilience. The way Porges explains this is by saying that newer neurons act first as part of our evolution as mammalians;

  • we get most of the explanations of the fight-flight-freeze response in the literature comparing humans to animals, but even when we are animals, we are not fighting for survival at all times, and there are not predators chasing us. Without the awareness (activation of the cortex and executive functions), we tend to submit to the survival strategies without consideration of why, resigned to not having the experience of fulfilled life. The extreme fear of dying, of suffering pain, of losing loved ones, of being rejected, or those inevitable life events is what our system equates to being caught by a predator. There are better ways out than giving up feeling; we are a very complex and evolved species with the opportunity to experience life in a very rewarding way beyond the rewards of eating, mating and resting. We can use the evolved part of our brains to regulate our fears and choose engagement with others —or with ourselves— in order to get the best possible outcome of being alive.

A little bit of history

It has been a long time since Walter Bradford Cannon used the term fight-or-flight in his book The Wisdom of the Body (1932) to describe the innate primitive response of the ANS for animals encountering danger (remember that the ANS is the one that reacts automatically, and its functioning is involuntary). He explained to the medical community how this response is a survival mechanism to confront or avoid an attack from a predator in order to survive. It was then discovered that humans have the same hardwired strategy to stay alive, even if they are not at risk of getting caught and eaten by a predator. In time, it was discovered that this survival mechanism is the origin of humans becoming traumatized, something that (as far as we know) most animals don’t suffer from. 

It was likely Peter Levin who brought the freeze-faint concept back into our vocabulary and awareness when he expanded on the concept in his book Waking the Tiger (1997). To explain trauma, Levin and others started incorporating the concept of freezing as the continuation of the animals’ strategy to avoid death if they couldn’t succeed in fighting or fleeing. 

The term fight-flight-freeze was then used to explain trauma (or PTSD) everywhere, as the sequence that happens while encountering the possibility of dying or losing one’s integrity, resulting in flashbacks, mood swings, emotional numbness, avoidance, and other symptoms that traumatized people suffer from. It has been a simple and easy way to understand that after the sympathetic activation (responsable for the fight-flight) does its thing by flooding the body with stress hormones, and fails, the parasympathetic (rest & digest) follows to numb the pain, reduce the bleeding, etc., to assure survival, and if the parasympathetic fails also, then the brain and ANS will adjust to a new “automatic” way of functioning for survival purposes, even at the cost of dysfunction, dissociation, pathology, and the overall well-being and mental-health of the person.

Even when the fear reaction is not necessarily chronological, the non-academics were content with the simplicity of the fight-flight-freeze model since it gave just enough technical information to bring attention to how pervasive trauma is, and how little we have done to prevent or resolve it. In response, the non-academics began to develop treatments to deal with trauma’s consequences by regulating the sympathetic/parasympathetic mechanisms. 

In 1994, Stephen Porges came out with the Polyvagal Theory ( challenging the previous understanding about the fight-flight-freeze functioning. Even when he puts a great emphasis on the connection between the ANS reactions to facial expressions and tone of voice, the trauma community and the academics noted the fact that the Polyvagal Theory proposes a mammalian behavior —social-engagement— that has both, calming and acting characteristics from the parasympathetic nervous system. Since the theory became relevant to understand trauma, several people have tried to marry both concepts to come with a clearer understanding of the ANS functioning: the extensively-described and used fight-flight-freeze model based on the sympathetic vs parasympathetic activation, with the new social-engagement-mobilization-immobilization model that Porges suggests. 

While tempting —and maybe necessary— I won’t go into detailing the biology here, but instead, will try to distinguish the different ways that our bodies freeze, and to explore what we could do differently by adding the social-engagement component. Most animals have no choice but to succumb to their instincts, but as humans, we could learn to identify our natural tendencies and to modify our responses to avoid not only death but illness and emotional malady. The key here will be to separate the primitive fear reaction that most animals experience from a more controlled, reasoned and chosen human one.

One of the most significant contributions from Porges’ theory is to explain that as an evolved species, we can feel protected and safe by connecting to others, instead of seeing others as enemies, and living life as if it were about constantly fighting and fleeing from them.

The Immobilization paradigm shift (the beginning of the confusion)

Porges challenged the previous consensus with his theory. 

Porges has made us think further and go deeper in observing all the different phases that we humans —as opposed to more primitive beings— go through when feeling trapped, unsafe, scared, rejected, intimidated, abandoned, ashamed, bullied, criticized, or any of those altering experiences or circumstances we suffer from, that end up causing isolation, disconnection, shock, mental disturbances, and psychological trauma. He has changed the paradigm by combining biology with attachment theory and evolution. His observations of 20+ years of research challenged an understanding of a century or more. It's not that easy to rewrite science and to make sense of all that had been written using the old ANS paradigm.

The ANS was classically divided into two subdivisions, the sympathetic and the parasympathetic and it was believed there was a paired antagonism between them, meaning that one is inhibited with the activation of the other; and that the vagus nerve was a single unit (the vagus is the principal nerve of the parasympathetic system).

Porges' theory, in contrast, differentiates brainstem areas that regulate the organs situated above the diaphragm (branching to the face, head, lungs, and heart) from  those regulating below the diaphragm (gut), depending on the myelinated and unmyelinated vagal pathways (ramifications of the vagus nerve extends from the head to the abdomen; myelinated refers to a fat layer covering the nerve, and a myelinated nerves send signals faster than an unmyelinated nerves).  

Not only did he tell us that we (as mammals) evolved by inheriting behavioral and physiological features from turtles, that semi-paralyzed faces could be more appealing for safety reasons, that face botox interferes with social connection, that trauma and evolution need to be considered more seriously, but also that the vagus is divided in 2: the ventral which is myelinated —newer, optimized, only on mammals— and the dorsal which is unmyelinated —older, primitive, shared by all vertebrates—; that the ANS is a system of three circuits in which newer circuits inhibit older circuits; that the ANS functioning is hierarchical instead of antagonistic (or looking only for equilibrium); and that the newest vagus controls vocalization and face expression-recognition as an added survival strategy.

As of today, there is a large group of scholars that are still debating the validity of Porges’ discoveries. 

In the meantime, while science debates and takes its time researching (mostly with animals) we need to keep treating, understanding and further educating ourselves about trauma and its consequences. We can't afford to ignore the differences between what has been introduced in the field recently, and our previous understanding of the fight-flight-freeze that became so pervasive. It is more evident than ever that trauma and attachment are seriously connected, and that trauma is an epidemic. Porges’ greatest contribution is to tell us that as evolved beings, our first strategy must be engaging with those around us, instead of fighting with each other or escaping from interpersonal connection. That concept alone could stop the epidemic if we understand its deep meaning.

Different terms used to explain immobilization when encountering danger that are commonly used to generalize the freeze response:

Some very smart scholars have played with words to describe the fear response to make it easier to memorize like in “Freeze-Flight-Fight-Fright-Flag-Faint” (Schwartz, 2014). There are other terms used to explain freeze like: Orienting, Fawn, Faint, Collapse, Feigned death, Submit, Immobilization, etc. I think they all share my concern about expanding the fight-fligh-freeze model. In my view, at least in this post, the order of the words are more important than the words themselves. Expanding the model means to find a sequence that explains the order of the strategies so that we have a broader picture of the origins of trauma and its symptomatology. Trauma has many faces. The following flow tries to include them all:

Survival Defenses Flow (criteria) 

The following flowchart contains all the phases I had been able to identify as part of the survival chain, consolidating the defense responses with the immobilization strategies. It integrates the information I learned through my studies on trauma and my special interest on FREEZE, giving singular attention to two recent articles. The first is by Kasia Kozlowska and a group of psychiatrists from the University of Sydney that published an article at the Harvard Review of Psychiatry Journal in 2015 proposing a five-level model to explain the defense reaction. That paper consolidates with extraordinary clarity the old model (sympathetic/parasympathetic) with the addition of Porges' polyvagal theory, and explains in detail all the neurobiology of each strategy. Kozlowska et. al called it "Defense Cascade”. The article describes studies made on animals but uses the still limited observations on humans to compare and assume similar mechanisms with extensive and very technical definitions of the freeze response (

It defines freeze as a “fight-flight put on hold.” When I read this definition and the neurobiology involved, I felt compelled to investigate further and to write this post because I was able to understand many of the behaviors I have seen in some clients that don’t fit in the common understanding of trauma but live in a “suspended” emotional dysregulated state. They live in a constant state of emotional rigidity (not physical one), and seems that they may have gotten stuck on that precise defense: fight-flight-on-hold.

Kozlowska et. al explain in detail the different neurobiology of each step of the cascade (, and the different systems that get activated in each (see table 1. below). The table shows that immobility and social-engagement are parasympathetic responses while fight-flight are sympathetic ones. The only one that has both active is Freeze.

A table with several columns and one row per activation type
Defense Cascade Detail

Even though Kozlowska’s model is such a great option to understand the "freeze" that describes immobilization in detail, it leaves out different reactions that we have mentioned as part of the variations of the “freeze umbrella”, including some reactions that concern Porges. For instance, many people use the word “freeze” to describe what animals do when they are initially assessing danger. In the Cascade Response model, they just talk about a phase they call Arousal; I find it necessary to expand on that stage to include the most relevant part of Porges’ theory. 

Porges describes "social-engagement" as the preamble of the mobilization strategy. “Social-engagement” is active as a basis of safety, and works by interpreting non-verbal signs including other people’s facial expressions, the intonation of their voice, body movements, gestures, and eye contact. When the person who feels threatened reaches out as the first resource for safety, the social-engagement mechanism is keeping the person aroused and calm at the same time. Porges doesn't include immobilization in this stage, but Karin Roelofs, a professor of Experimental Psychopathology in the Netherlands, published an article in 2017 called "Freeze for action: neurobiological mechanisms in animal and human freezing"  where she describes "Freezing is activated at intermediate levels of predator threat. It is a state of attentive immobility serving to avoid detection by predators and to enhance perception" ( Even when the description sounds similar to the fight-flight-on-hold, Roelofs uses the term “attentive immobility” that seems preventive without consequences. If that’s the case, the level of activation of the ANS would be less intense than when immobilization is activated, and therefore, the after effects less significant. 

If we add the neurobiology and the Polyvagal Theory, there is space in the “cascade” or flow for the social-engagement that’s so important for Porges explaining his theoretical model, and for attentive immobility as well. 

If I keep the word freeze that Kouslowska uses, we will keep confusing freeze with immobilization. We need a different word. I’d like to propose a new term — LOCK. The LOCK reaction describes Kozlowska’s “freeze” condition as fight-flight-on-hold, but specifically for humans. LOCK state happens before fight-flight and is different from immobilization and even from attentive immobilization. The word LOCK amplifies the consequences of the mechanism. This stage could make the ANS to respond to threat and getting stuck in a “locked” reactivity where sympathetic and parasympathetic are both ready to do their tasks —independently and at the same time. Those who exhibit LOCK symptomatology are functional people, but carry with them a rigid way of looking at their own capabilities and potential, as well as a closed and apprehensive way of looking at the world around them. I see many examples of LOCK in my daily practice, and want to draw the attention towards this common and under-explored area of trauma.

That way, as I show in my diagram, attentive immobility comes as a consequence of the effort to "orient" typical of the social-engagement task, and/or after social-engagement failure, and LOCK comes after an increased or failed attentive immobility. With this, all the different ways the body reacts that could be perceived as “still” or frozen, without necessarily being paralyzed or immobile, are covered.

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