Fight or Flight Response (Psychology) – 15 Examples (2023)

The fight or flight response is a rapid and intense physiological reaction to immediate and sudden danger. It is activated in situations in which a person encounters a life-threatening or highly stressful situation.

Fight or flight is a highly adaptive survival mechanism that is biologically ingrained in every human being as well as animals (meaning it is an unconditioned response).

Examples of flight or fight include the immediate response to seeing a snake while hiking, being startled down a dark alley, or being caught by a police radar while speeding in your car.

Once a person encounters impending danger, a cascade of hormonal and electrochemical reactions take place that prepare the body to either fight or flee.

Physiologist Walter Cannon was the first to describe the fight-or-flight response in 1915.

Cannon explains that:

“…the visceral changes in fear and rage should not be different, but rather, why they should be alike… just because the conditions which evoke them are likely to result in flight or conflict…the bodily needs in either response are precisely the same” (p. 277).

Modern understanding of this response acknowledges that the organism may also freeze in position, or even faint. This new perspective has led to the term “fight, flight, or freeze” (Donahue, 2020) or “acute stress response.”

The physiological response to the stressor begins with the detection of danger. Amazingly, this detection can happen faster than the conscious awareness of the impending threat.

For example, if walking through the forest and encountering a snake, that image is sent via the optic nerve to the amygdala located in the limbic system.

The amygdala immediately sends electrical impulses via the spinal cord to various muscles that create the startle response, such as jumping away.

In a second pathway, the amygdala triggers the hypothalamus, which triggers the pituitary gland to release adrenocorticotropic hormones (ACTH).

ACTH flows through the blood stream to impact the adrenal glands that sit atop the kidneys and activates the release of cortisol. Cortisol increases blood pressure, blood sugar and turns fatty acids into available energy.

The adrenal glands also release adrenaline, which stimulates the release of glucose (for energy), in addition to increasing heart and respiratory rate.

These various mechanisms fill the muscles with blood and supply the body with much-needed oxygen and energy. All of which are required to either fight or flee.

Dr. Hans Seyle formulated the general adaptation syndrome (GAS) to describe the stages of the stress response. The GAS is an extension of the fight-or-flight response and includes components that enhance our understanding of how the body reacts to stressful events.

There are three stages of the GAS.

The physiological changes activated by the fight-or-flight response have been highly adaptive for thousands of years. In modern times, there is less need for this response. However, modern life is full of minor stressors, or symbolic threats, that activate a mild expression of the fight-or-flight response. 

Health researchers have linked stressful life events in modern life with health outcomes such as heart disease for decades (Levine, 2022).

More specifically, stressful life events, ranging from major catastrophes (e.g., earthquakes) to high-pressure job demands, have been linked to myocardial infarction (MI) and atherosclerosis (e.g., hardening of the arteries). 

For example, Möller et al. (2005) examined stressful occupations and the incidence of MI. The researchers state that in their study they found:

“…that life events experienced in working life, and characterized by high demands, competition, or conflict, are potential triggers of the onset of myocardial infarction” (p. 27).

The chemical reactions activated by the fight-or-flight response also increase cholesterol levels and reduce the elasticity of the coronary walls over time.

In addition to other factors such as lifestyle and personality characteristics, the impact of stress on health can be substantial.

The first pathway of the fight-or-flight response happens before conscious awareness. The nerves in the eyes have a direct connection to the amygdala in the limbic system.

There are certain images that have been programmed into the amygdala to activate an immediate reaction.

Apparently, for cats, one of those images is of a snake. This means that visual stimuli that are similar to a snake, such as a cucumber, can also activate the fight-or-flight response.

In this video, and about a hundred others, cats can be seen having dramatic flight response when encountering a cucumber. Since the vegetable is similar in shape and size to a snake, the cat’s reaction is understandable.

The reaction takes place well in advance of the cat being able to consciously process the visual image to determine that it is not a snake.

From an evolutionary perspective, this is very beneficial. In the wild, by the time a cat was able to cognitively process the stimulus, it would be too late if it were an actual snake.

By now, just about everyone on the planet has seen a video of The Scary Snowman prank. As passers-by casually stroll along a sidewalk, a large stationary snowman jumps forward. This creates a variety of reactions, sometimes humorous.

Generally, most people have a reasonable response, however, some get a bit upset and a few choice words may be uttered. One person actually kicks the snowman, while one elderly gentleman looks like he might have a cardiac arrest.

Some people literally jump, sometimes up, sometimes backwards, and sometimes straight to the ground. And a lot of people let out a loud scream as well.

All joking aside, these physical reactions are good examples of the fight-or-flight response in action. You can see how instantaneously those reactions occur. The human body really is amazing.

Given how serious life stressors can become, it may be useful to identify strategies that an individual can take to help combat those detrimental effects.

Luckily, there are numerous things a person can do to reduce the impact of stress. These include:

The fight-or-flight-or freeze response refers to the sudden activation of several physiological chain reactions when encountering danger. The danger can be very real and life-threatening, or in the form of a symbolic threat as found in modern life.

The physiological reaction prepares the body for physical action, either running or engaging in a physical altercation. In other cases, it may cause the body to temporarily freeze and become motionless.

Although highly adaptive for most of human history, the problem now is that modern life is full of minor activations of the stress response. Over a long period of time, that can lead to physical illness such as a heart attack, or psychological issues such as mental fatigue and burnout.

Fortunately, people can integrate various strategies in their life to counteract these detrimental consequences.

Developing a more optimistic interpretation of events, exercising and sleeping well, and building a supportive circle of significant others can all help mitigate the stress response.

Cannon, W. B. (1915). Bodily changes in pain, hunger, fear and rage: An account of recent researches into the function of emotional excitement. D Appleton & Company. https://doi.org/10.1037/10013-000

Donahue, J.J. (2020). Fight-Flight-Freeze System. In: Zeigler-Hill, V., Shackelford, T.K. (Eds.) Encyclopedia of Personality and Individual Differences. Springer, Cham. https://doi.org/10.1007/978-3-319-24612-3_751

Larzelere, M. M., & Jones, G. N. (2008). Stress and health. Primary Care, 35(4), 839–856. https://doi.org/10.1016/j.pop.2008.07.011

Levine, G. N. (2022). Psychological Stress and Heart Disease: Fact or Folklore? The American Journal of Medicine, 135(6), 688-696.

Möller, J., Theorell, T., De Faire, U., Ahlbom, A., & Hallqvist, J. (2005). Work related stressful life events and the risk of myocardial infarction. Case-control and case-crossover analyses within the Stockholm heart epidemiology programme (SHEEP). Journal of Epidemiology & Community Health, 59(1), 23-30.

Perciavalle, V., Blandini, M., Fecarotta, P., Buscemi, A., Di Corrado, D., Bertolo, L., Fichera, F. & Coco, M. (2017). The role of deep breathing on stress. Neurological Sciences, 38(3), 451-458.

Salmon, P. (2001). Effects of physical exercise on anxiety, depression, and sensitivity to stress: a unifying theory. Clinical Psychology Review, 21(1), 33-61.

Selye, H. (1950). Stress and the general adaptation syndrome. British Medical Journal, 1(4667), 1383–1392. https://doi.org/10.1136/bmj.1.4667.1383

Thoits, P. A. (2010). Stress and health: Major findings and policy implications. Journal of Health and Social Behavior, 51(1_suppl), S41-S53.

Dr. Cornell has worked in education for more than 20 years. His work has involved designing teacher certification for Trinity College in London and in-service training for state governments in the United States. He has trained kindergarten teachers in 8 countries and helped businessmen and women open baby centers and kindergartens in 3 countries.

This article was peer-reviewed and edited by Chris Drew (PhD). The review process on Helpful Professor involves having a PhD level expert fact check, edit, and contribute to articles. Reviewers ensure all content reflects expert academic consensus and is backed up with reference to academic studies. Dr. Drew has published over 20 academic articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education and holds a PhD in Education from ACU.