Understanding the Fight-or-Flight Response in Psychology

The fight-or-flight response is an instinctual cascade of physiological events that has safeguarded the survival of humans throughout evolution. This primal reflex, deeply embedded in our nervous system, is activated in the face of perceived threats. This system mobilizes the body for quick action—to stand ground and confront or to take flight and evade. As we delve into the complexities of this response, we uncover not only the biological underpinnings but also the psychological ramifications. The fight-or flight response is deeply woven into the fabric of modern human experience. This article aims to explore the origins, mechanisms, and impacts of the fight-or-flight response, shedding light on its role in contemporary life and its significance in the field of psychology.

Understanding the Fight-or-Flight Response

The fight-or-flight response is governed by the sympathetic nervous system, which activates when our brain perceives a threat. When faced with danger, such as encountering a predator or experiencing extreme stress, our body releases stress hormones like adrenaline and cortisol. These hormones trigger various changes in the body to prepare us for action.

Walter Cannon (1915) developed the concept of the “fight or flight” response, which describes the body’s automatic physiological reaction to a perceived harmful event, attack, or threat to survival. His theory states that animals, including humans, react to threats with a general discharge of the sympathetic nervous system, preparing the organism for fighting or fleeing.

Here are the key points of Cannon’s theory:

• Sympathetic Nervous System Activation: When faced with a threat, the body activates the sympathetic nervous system, which leads to a series of physiological changes in the body.
• Adrenaline Release: The adrenal glands release adrenaline (epinephrine), which results in increased heart rate, higher blood pressure, faster breathing, and heightened senses.
• Preparation for Action: These physiological changes prepare the body to either fight the threat or flee from it, hence the term “fight or flight.”
• Homeostasis: Cannon also related this response to the concept of homeostasis, which is the body’s way of maintaining a stable internal environment. The fight or flight response is part of the body’s short-term survival mechanism to restore homeostasis in the face of immediate danger.

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Cannon’s work laid the foundation for our understanding of stress responses and how the body reacts to emergencies and threats. It’s a critical part of the field of psychophysiology. Theorists and researchers have expanded on Cannon’s original theory.

See the Sympathetic Nervous System for more on this topic

Physiological Changes

During the fight-or-flight response, several physiological changes occur to help us respond effectively to danger.

During the fight or flight response, a series of physiological changes occur in the body to prepare an individual to confront or flee from a perceived threat. The sympathetic nervous system orchestrates these changes. They may include:

• Increased Heart Rate and Blood Pressure: To quickly pump blood to vital organs and muscles.
• Rapid Breathing: To increase oxygen intake for heightened alertness and muscle readiness.
• Redistribution of Blood Flow: Blood is diverted from non-essential functions to muscles needed for action.
• Dilated Pupils: To allow more light into the eyes and improve vision.
• Pale or Flushed Skin: Due to the redirection of blood flow, which can also cause goosebumps.
• Reduced Pain Sensitivity: To focus on the threat without being hindered by pain.
• Tense Muscles: Preparing the body for sudden movement.
• Heightened Senses: To be more aware of the surroundings.
• Changes in Digestion: Digestive processes slow down as the body prioritizes immediate survival.
• Release of Stored Energy: Increased blood glucose levels provide a quick energy source.

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These changes are part of the body’s innate survival mechanism, enabling a rapid response to danger. Peter Levine explains that when you perceive a threat, “your nervous system and body prepare you to kill or to take evasive countermeasures to escape, usually by running away” (Levine, 2012).

What Triggers The Fight-or-Flight Response?

We have a few natural fears that trigger stress. However, we most threats we learn from experience and observation. We learn what circumstances destabilize our system. Gabor Maté explains: “The stress response is non-specific. It may be triggered in reaction to any attack—physical, biological, chemical or psychological—or in response to any perception of attack or threat, conscious or unconscious. The essence of threat is a destabilization of the body’s homeostasis, the relatively narrow range of physiological conditions within which the organism can survive and function”

Maté continues: “To facilitate fight or escape, blood needs to be diverted from the internal organs to the muscles, and the heart needs to pump faster. The brain needs to focus on the threat, forgetting about hunger or sexual drive. Stored energy supplies need to be mobilized, in the form of sugar molecules. The immune cells must be activated. Adrenaline, cortisol and the other stress substances fulfill those tasks” (Maté, 2008).

Daniel Siegel posits that word “no” often elicits the reactive brainstem states of fight–flight–freeze. “No” is often spoken in response to an expressed need or want. Naturally, then, the response arouses are system. In contrast, “Yes” activates “the state of openness and social engagement, involving limbic and prefrontal modulation of the state of reactivity to one of receptivity” (Siegel, 2020).

Fight-or-Flight Arousal is Measured on a Continuum

Like many psychological processes, we speak of them as if they work like an on-off switch. Arousal is measured. Large threats trigger large reactions. Small threats provoke much less arousal. Our bodies conserve energy. Accordingly, threats only initiate the amount of response (release of adrenaline) sufficient to meet the predicted level of action to overcome the threat. Vilayanur Subramanian Ramachandran, a neuroscientist, explains that the fight-or-flight “reaction is not all or nothing; it operates on a continuum. A mildly, moderately, or profoundly emotional experience elicits a mild, moderate, or profound autonomic reaction, respectively” (Ramachandran, 2011).

Impact on Mental Health

Understanding the fight-or-flight response is essential in psychology as it plays a significant role in mental health conditions like anxiety disorders and post-traumatic stress disorder (PTSD). People who experience chronic stress may have an overactive fight-or-flight response, leading to persistent feelings of anxiety and hypervigilance.

Maté wrote: “Discharges of nervous system, hormonal output and immune changes constitute the flight-or-fight reactions that help us survive immediate danger. These biological responses are adaptive in the emergencies for which nature designed them. But the same stress responses, triggered chronically and without resolution, produce harm and even permanent damage. Chronically high cortisol levels destroy tissue. Chronically elevated adrenaline levels raise the blood pressure and damage the heart” (Maté, 2008).

We refer to stress that constantly activates the fight-or-flight response as toxic stress. The value of this oversensitive system diminishes as the false alarms of danger constantly ring, triggering adrenaline production, and slowly damaging tissue.

Maladaptive Responses

We must listen to our bodies. However, this does not mean that our bodies are correctly interpreting the environment or motivating an adaptive response. Our bodies are simply signalling arousal to some stimuli that may or may not be important. Because most of our fears are learned, and learning is subject to error, the arousal may not be appropriate for the circumstances.

Harriet Lerner wrote in regards to social anxiety that, “We do need to protect ourselves when the feelings evoked by connecting are unmanageable or simply too painful. Withdrawal does relieve anxiety and intensity. The flight response (like the fight response) is wired into us for good reason.” She continues: “As physical pain tells us to get our hands out of the fire, our fear tells us—once we’ve been burned—to be cautious about fire the next time around. The fight-or-flight response that anxiety evokes can save our lives—that is, if either fighting or fleeing happens to be the wisest thing to do in the face of a present danger” (Lerner, 2005).

The point she is making is that fight-or-flight is not always appropriate. If we experience arousal (fight-or-flight) at the thought of any and every social interaction, and respond through flight (avoidance), we miss out on one of the greatest environmental elements contributing to wellness—others. Discomfort is a low level activation of the system, however, often the best response is to cope with the discomfort and step towards the frightening element. Only in discomfort do we expand and grow.

Coping Strategies

Once we determine that our system is overacting, prompting maladaptive reactions, we may need to employ methods to soothe the arousal, returning our sympathetic nervous system back to a homeostatic state. Learning how to regulate the fight-or-flight response can be beneficial for managing toxic stress and allowing for adaptive responses.

Coping strategies in the context of the fight-or-flight response are techniques that help manage the physiological and psychological reactions triggered by a perceived threat or stressor. Basically, coping strategies counteract the cascade of hormonal and nervous system changes, returning to the body to a normal heart rate, relaxed breathing, and curious openness.

List of Strategies

Here are some coping strategies that can help mitigate the fight-or-flight response:

• Deep Breathing: Slow, deep breaths can activate the parasympathetic nervous system, which counteracts the fight-or-flight response. This helps to reduce heart rate and promote a sense of calm.
• Relaxation Techniques: Methods like progressive muscle relaxation, meditation, and guided imagery can help relax the body and mind, reducing the intensity of the fight-or-flight reaction.
• Physical Activity: Engaging in exercise can help burn off the excess energy generated by the fight-or-flight response, and it can also release endorphins, which are natural mood lifters.
• Social Support: Talking to friends, family, or a therapist can provide emotional support and help put the stressor into perspective, making it feel less threatening.
• Positive Self-Talk: Replacing negative thoughts with positive affirmations can help reduce anxiety and improve the ability to handle stress.
• Visualization Techniques: Imagining a peaceful scene or a successful outcome can distract from the stressor and reduce the body’s stress response.
• Mindfulness: Being present in the moment and accepting one’s feelings without judgment can help manage stress and reduce the impact of the fight-or-flight response.

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We can practice these strategies regularly to build resilience against stress. They also provide a means to quickly calm down when the environment triggers the fight-or-flight response. It’s important to note that while these strategies can be effective, they may not work for everyone or in every situation. It may be necessary to try different techniques to find what works best for an individual.

History of the Concept of ‘Fight-or-Flight Response’

The concept of the fight-or-flight response has a significant history in psychology, primarily attributed to the work of American physiologist Walter Bradford Cannon. Here’s a brief overview of its historical development:

• Early 20th Century: Walter Cannon introduced the concept “fight-or-flight” in the early twentieth century.. However, after searching his early works, I did not find him actually use the term “fight-or-flight.” He does however explain in detail the organisms physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival (Cannon, 1915).
• Cannon’s Research: In his seminal work, Cannon observed that animals react to threats with a general discharge of the sympathetic nervous system, preparing the organism for fighting or fleeing. This response is characterized by the release of hormones such as adrenaline and noradrenaline from the adrenal glands, which would lead to increased heart rate, blood pressure, and energy supplies (Cannon, 1932).

Stress

• Expansion of the Concept: Over the years, psychologists and physiologists have expanded upon Cannon’s original concept. The fight-or-flight response is now understood to be part of a broader set of reactions to stress, which can also include freezing, fainting, and appeasing behaviors (Selye, 1951).
• Acute Stress Response: Science recognizes Cannon’s fight-or-flight response as the first stage of the general adaptation syndrome. General adaptation syndrome regulates stress responses among vertebrates and other organisms. It is a built-in defense mechanism evolved to enhance survival by readying an organism for danger through physiological changes. This automatic reaction to threats enables an organism to defend itself rapidly from a perceived danger.

Freeze

• Modern Understanding: Today, the fight-or-flight response is still a central concept in understanding how humans and other animals respond to stress. Most research agrees that freeze is in a third possible reaction to sympathetic nervous system arousal. Modern science considers the fight-or-flight response as part of our evolutionary heritage, equipping us with the mechanisms to deal with threats quickly and effectively.

Neurobiology of Fight-or-Flight Response

Ramachandran explains the path from perception to arousal in neurobiology terms this way: “Once meaning is extracted in these bottleneck regions, the messages are relayed to the amygdala, which lies embedded in the front tip of the temporal lobes, to evoke feelings about what (or whom) you are seeing.” He continues to explain that if it is an intense feeling, “the signals from the amygdala also cascade into your hypothalamus, which not only orchestrates the release of hormones but also activates the autonomic nervous system to prepare you to take appropriate action, whether it’s feeding, fighting, fleeing, or wooing.” He then adds: “These autonomic responses include all the physiological signs of strong emotion such as increased heart rate, rapid shallow breathing, and sweating” (Ramachandran, 2011).

Constructivism and Arousal

Ramachandran has added a slight twist to Cannon’s original proposal as a response to a threat. He includes emotional reactions to opportunity in the same process. He explains: “When you look at something that’s emotionally evocative—a tiger, your lover, or indeed, your mother—your amygdala signals your hypothalamus to prepare your body for action” (Ramachandran, 2011). the action may be to fight, flee, or approach, depending on the nature of the stimulus.

Sheri van Dijk also points out that the “fight-or-flight” response is not a distinct emotion but an arousal. In describing the response she wrote: “Because the same fight-or-flight response is triggered when you feel anger or fear, the similar sensations can make it difficult to figure out which emotion it is that you’re feeling, so it’s important to think hard about the situation you’re in when the emotion arises and to think about your thoughts and urges in this situation” (van Dijk, 2012, p. 56). We refer to this as emotion constructionism.

Basically, we label the arousal with an emotion based on context.

See Constructivist Psychology for more on this topic

PTSD and the Fight-or-Flight Response

Theorists associate several anxiety disorders, including Post Traumatic Stress Disorder to the fight-or-flight response system. A common theory is that when the response system is unable to complete the cycle (stresser, arousal, resolution) that the event may continue to disrupt or emotional balance.

Levine explains that the meaningful action in response to the arousal discharges the energy, allowing the organism to restore vital balance back to their system. He goes on to say: “However, in order to experience this restorative faculty, we must develop the capacity to face certain uncomfortable and frightening physical sensations and feelings without becoming overwhelmed by them” (Levine, 2012). It is the incompleteness of resolution, often associated with the freeze state, that commonly leads to anxiety disorders.

Levine posits that when “these ‘discharges’ are inhibited or otherwise resisted and prevented from completion, our natural rebounding abilities get ‘stuck.’” He concludes this thought, stating that being stuck, after an actual or perceived threat, “means that one is likely to be traumatized or, at least, to find that one’s resilience and sense of OK-ness and belonging in the world have been diminished” (Levine, 2012).

Childhood Conditioning

Childhood is the school yard for learning all the necessary skills for surviving as an adult. Beyond simple social skills, children learn methods for dealing with arousal. Basically, arousal is a response to a perceived need or threat to obtaining a need. The interaction with primary figures in a child’s life helps pave the way for a lifetime of managing these fight-or-flight arousals.

Maté explains that children “exposed to acute and chronic stress by their childhood conditioning, and their ability to engage in the necessary flight-or-fight behaviour was impaired. The fundamental problem is not the external stress, …but an environmentally conditioned helplessness that permits neither of the normal responses of fight or flight. The resulting internal stress becomes repressed and therefore invisible” (Maté, 2008).

For example, infants express their need for touch, nourishment, love, and connection at first by fussing and crying, which is simply an expression of healthy aggression. It is a sympathetic nervous system arousal, attempting to secure a need.

However, explains Lawrence Heller, when the need is not appropriately responded to “the infant escalates the demand, ramping up the sympathetic branch of the autonomic nervous system, protesting the lack of response, and finally erupting into anger. In neglectful and abusive environments, when lack of adequate response is chronic, anger and aggression cannot be resolved. When infants feel chronic anger toward their caregiver, it is instinctively experienced as a threat to the attachment relationship and therefore as dangerous to survival. Symptoms of undischarged sympathetic activation develop, leaving children, and later adults in states of high arousal, anxiety, and irritability, prone to temper outbursts, fearfulness, and even panic attacks” (Heller & LaPierre, 2012).

Basically, we learn patterns through experience or through modeling on how to effectively utilize our built in fight-or-flight response.

Evolutionary Significance

The fight-or-flight response is a fundamental survival mechanism that evolved to enable animals, including humans, to react swiftly to life-threatening situations. The sympathetic nervous system triggers this response to prepare the body to either confront the danger (fight) or escape from it (flight). Here’s a detailed look at its evolutionary significance:

• Survival of the Fittest: The fight-or-flight response is one of the most basic survival instincts with a very long evolutionary history, conserved across species. It evolved as a way for animals to become aware of immediate danger and to act in a manner that maximizes their chances of survival.
• Physiological Changes: When an event activates the fight-or-flight response, several physiological changes occur. The adrenal glands secrete adrenaline, increasing heart rate and respiration, sharpening senses like sight and hearing, and sometimes stimulating sweat glands. These changes prepare the body for the necessary action to survive the threat.
• Evolutionary Psychology: From an evolutionary psychology perspective, early animals needed to respond to threats quickly without the time for psychological and physical preparation. The fight-or-flight response provided them with the mechanisms to rapidly respond to threats against survival.
• Sympathetic Nervous System: Scientists previously believed that the sympathetic nervous system, which controls the fight-or-flight response, evolved with jawed vertebrates. However, recent research on lampreys, a jawless vertebrate, suggests that even the earliest vertebrates may have had a rudimentary version of this system. The sympathetic nervous system has deep evolutionary roots.

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In essence, the fight-or-flight response is an adaptive trait continuing for over millions of years. The trait survived because of its effectiveness in enhancing organism’s survival and reproductive success. It helps organisms survive immediate danger. An example of how evolutionary pressures shape physiological and behavioral traits crucial for the survival of a species.

Associated Concepts

• General Adaptation Syndrome (GAS): Developed by Hans Selye, this theory describes the body’s short-term and long-term reactions to stress. GAS outlines three stages: alarm (similar to fight-or-flight), resistance, and exhaustion.
• Polyvagal Theory: Proposed by Stephen Porges, this theory expands on the fight-or-flight response. Porges theory introduces the concept of the social engagement system. It emphasizes the role of the vagus nerve in emotion regulation, social connection, and fear response.
• Stress-Diathesis Model: This model suggests that physiological stress responses, like fight-or-flight, can result from the interaction between environmental stressors and an individual’s biological predisposition.
• Cognitive Appraisal Theory: Developed by Lazarus and Folkman, this theory focuses on the individual’s cognitive assessment of a stressor as a primary factor in determining the physiological stress response.
• Homeostasis: Although not a theory, the concept of homeostasis is relevant as the fight-or-flight response is part of the body’s attempt to maintain internal stability in the face of external changes.
• Allostasis and Allostatic Load: Allostasis refers to the process by which the body responds to stressors to regain homeostasis. Allostatic load is the wear and tear on the body that accumulates through exposure to repeated or chronic stress.
• Yerkes-Dodson Law: This law posits that there is an optimal level of arousal for performance. Accordingly, too much or too little arousal can impair performance. The fight-or-flight response is related to the arousal level in this context.

A Few Words by Psychology Fanatic

In conclusion, the fight-or-flight response is a testament to the intricate design of the human body—a system honed by evolution to protect us from imminent danger. However, in our modern world, where psychological stressors predominate, modern events can trigger this primal reaction inappropriately. Our experience of stress and the fight-or flight response may lead to chronic stress and its myriad of health implications. As we continue to unravel the complexities of this response, it is crucial that we develop effective coping strategies that can mitigate its effects and promote resilience. By fostering a deeper understanding of the underlying mechanisms, we empower individuals to harness this innate response not as a source of distress, but as a catalyst for growth and adaptation. The fight-or-flight response, once vital for our ancestors’ survival, we must now recontextualized as a challenge to manage, ensuring that it serves our well-being in the 21st century.

Last Update: August 22, 2025

References:

Cannon, Walter B. (1915). Bodily changes in pain, hunger, fear, and rage.
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Cannon, Walter B. (1932). The wisdom of the body. W W Norton & Co.
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Heller, Lawrence; LaPierre, Aline (2012). Healing Developmental Trauma: How Early Trauma Affects Self-Regulation, Self-Image, and the Capacity for Relationship. North Atlantic Books; 1st edition.
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Lerner, Harriet (2005). The Dance of Fear: Rising Above Anxiety, Fear, and Shame to Be Your Best and Bravest Self. ‎Perennial Currents; Reprint edition.
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Levine, Peter A. (2012). In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness. North Atlantic Books; 1st edition.
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Maté, Gabor (2008). When the Body Says No. ‎Trade Paper Press; 1st edition.
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Ramachandran, Vilayanur Subramanian (2011). The Tell-Tale Brain: A Neuroscientist’s Quest for What Makes Us Human. W. W. Norton & Company; Reprint edition.
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Selye, Hans (1951). The General-Adaptation-Syndrome. Annual Review of Medicine, 2(1), 327-342.
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Siegel, Daniel J. (2020). The Developing Mind: How Relationships and the Brain Interact to Shape Who We Are. The Guilford Press; 3rd edition.
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Van Dijk, Sheri (2012). Calming the Emotional Storm: Using Dialectical Behavior Therapy Skills to Manage Your Emotions and Balance Your Life. New Harbinger Publications.
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