The fight-or-flight response also called the acute stress response, is a physiological reaction triggered by fear or danger, whether physical or psychological. This reaction occurs when the body releases hormones that prepare it to either confront a threat or escape to safety.
The term "fight-or-flight" reflects the two main options early humans had when facing danger in their surroundings: to either defend themselves or flee. Regardless of the choice, this stress response equips the body to handle the situation.
First identified in the 1920s by American physiologist Walter Cannon, this response was recognized as a series of rapid bodily reactions that help individuals cope with immediate threats. Today, it is understood as part of the initial stage of Hans Selye’s general adaptation syndrome, a model that explains how the body responds to stress.
What Happens During the Fight-or-Flight Response
When the body experiences acute stress, the sympathetic nervous system is activated, triggering a surge of hormones. This activation causes the adrenal glands to release catecholamines, including adrenaline and noradrenaline. As a result, heart rate, blood pressure, and breathing rate increase. Once the perceived threat is gone, the body typically takes 20 to 60 minutes to return to its normal state.
Most people have experienced the fight-or-flight response at some point. Whether facing a sudden danger or preparing for a high-stakes event, physical changes take place. The heart beats faster, breathing quickens, and the body tenses in preparation for action.
This response can be triggered by a direct physical threat, such as encountering an aggressive dog while jogging, or by a psychological stressor, like preparing for a public presentation. Some common physical signs that indicate the fight-or-flight response has been activated include:
Increased Heart Rate and Breathing – The body boosts heart rate and respiration to ensure enough oxygen and energy are available for a quick reaction.
Changes in Skin Color – Blood flow is redirected away from the skin to the muscles, brain, arms, and legs. This can cause the skin to appear pale or flushed as circulation adjusts. Additionally, the body’s blood clotting ability increases to reduce potential blood loss in case of injury.
Dilated Pupils – The pupils expand to allow more light in, enhancing vision and awareness of the surroundings.
Muscle Tremors – As muscles tense in preparation for action, trembling or shaking may occur due to heightened readiness.
Why It Matters
The fight-or-flight response is a crucial part of how humans react to stress and danger. It prepares the body to either confront a threat or escape from it. This response can be triggered by both real dangers and perceived threats that exist only in the mind.
This response can enhance performance under pressure by getting the body ready for action. In high-stakes situations, such as exams, work presentations, or competitions, the stress response can improve focus and efficiency. In life-threatening circumstances, it plays an even more essential role by increasing the chances of survival.
Although this reaction happens automatically, it is not always accurate. Sometimes, it is activated when no real danger exists. Phobias provide a clear example of this. For instance, someone with a fear of heights may feel intense anxiety when required to go to the top floor of a tall building. Their heart rate may spike, and their breathing may become rapid, even though they are not in actual danger. If the response is extreme, it may result in a panic attack.
Understanding how the body naturally reacts to stress can help in managing such situations. Recognizing when tension builds allows individuals to use relaxation techniques to regain control.
The study of stress responses is a major area of focus in health psychology. Experts in this field work on strategies to help people manage stress more effectively. By learning more about how the body responds to perceived threats, psychologists can develop better ways to help individuals cope with stress and lead healthier lives.
Mary Watson
