Fight-or-Flight Response - Why Is It Important?

Experiencing the fight-or-flight response
The fight-or-flight response prepares your body to deal with stressors. Jamie Grill / Getty Images

The fight-or-flight response, also known as the acute stress response, refers to a physiological reaction that occurs in the presence of something that is terrifying, either mentally or physically. The response is triggered by the release of hormones that prepare your body to either stay and deal with a threat or to run away to safety.

The fight-or-flight response was first described in the 1920s by American physiologist Walter Cannon.

Cannon realized that a chain of rapidly occurring reactions inside the body helped to mobilize the body's resources to deal with threatening circumstances.Today the fight-or-flight response is recognized as part of the first stage of Hans Selye's general adaptation syndrome, a theory describing the stress response.

What Happens During the Fight-or-Flight Response?

In response to acute stress, the body's sympathetic nervous system is activated due to the sudden release of hormones. The sympathetic nervous systems stimulate the adrenal glands triggering the release of catecholamines, which include adrenaline and noradrenaline. This results in an increase in heart rate, blood pressure, and breathing rate. After the threat is gone, it takes between 20 to 60 minutes for the body to return to its pre-arousal levels.

You can probably think of a time when you experienced the fight-or-flight response.

In the face of something frightening, your heart beat quickened, you begin breathing faster, and your entire body become tense and ready to take action. This response can happen in the face of an imminent physical danger (such as encountering a growling dog during your morning jog) or as a result of a more psychological threat (such as preparing to give a big presentation at school or work).

The Importance of the Fight-or-Flight Response

The fight-or-flight response is also known as the acute stress response. Essentially, the response prepares the body to either fight or flee the threat. It is also important to note that the response can be triggered due to both real and imaginary threats.

By priming your body for action, you are better prepared to perform under pressure. The stress created by the situation can actually be helpful, making it more likely that you will cope effectively with the threat. This type of stress can help you perform better in situations where you are under pressure to do well, such as at work or school. In cases where the threat is life threatening, the fight-or-flight response can actually play a critical role in your survival. By gearing you up to fight or flee, the fight-or-flight response makes it more likely that you will survive the danger.

One thing to remember is that while the fight-or-flight response happens automatically, that does not mean that it is always accurate.

Sometimes we respond in this way even when there is no real threat. Phobias are good examples of how the fight-or-flight response might be triggered in the face of a perceived threat. A person who is terrified of heights might begin to experience the acute stress response when he has to go the top floor of a skyscraper to attend a meeting. His body might go on high alert as his heart beat and respiration rate increase. When this response becomes severe, it may even lead to a panic attack.

Understanding the body's natural fight-or-flight response is one way to help cope with such situations. When you notice that you are becoming tense, you can start looking for ways to calm down and relax your body.

The stress response is one of the major topics studied in the rapidly-growing field of health psychology. Health psychologists are interested in helping people find ways to combat stress and live healthier, more productive lives. By learning more about the fight-or-flight response, psychologists can help people explore new ways to deal with their natural reaction to stress.

More Psychology Definitions: The Psychology Dictionary


Cannon, W.B (1915). Bodily Changes in Pain, Hunger, Fear and Rage: An Account of Recent Researches into the Function of Emotional Excitement. Appleton-Century-Crofts.

Harari, P., & Legge, K. (2001). Psychology and Health. London: Heinemann Educational Publishers.

Teatero, M.L., & Penney, A.M. (2015). Fight-or-flight response. In I. Milosevic & R.E. McCabe, (Eds.), Phobias: The Psychology of Irrational Fear. Santa Barbara, CA: Greenwood.

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