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"Fight or Flight" May Be More Literal Than We Thought

When faced with a threat to survival, animals default to "fight or flight," also known as an "acute stress response." That triggers a set of physiological changes, preparing the body to either either fight or flee from danger. From the smallest insects to the largest mammals, all members of the animal kingdom are wired to protect themselves from injury or death. Now a team of scientists from the University of Utah are claiming that at the individual level, we may be built for only one response or the other.

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Fight, Flight, or Freeze

"Fight or flight" was first identified in the 1920s by physiologist Walter Canon, as a series of immediate changes in the nervous systems and other body systems in response to a perceived threat, in order to avoid or lessen the possibility of bodily harm. Eventually, a sequence of activities (set in motion by the hypothalamus) was pinpointed, including changes in the autoimmune, endocrine system, and immune systems. In turn, those changes and accompanying surge of hormones (including cortisol) may result in a number of physical symptoms including rapid heartbeat, anxiety, sweating, dry mouth, and increased sensitivity to sounds, among others.

All of these physiological changes result in an overarching, automatic response: "fight," confronting the threat, "flight," fleeing the threat. There is also a third response, "freeze," or playing dead in order to be less enticing to a predator looking for something to eat.

The Mouse-Olympics

Noting that some body types are better suited for certain activities over others, the team from the University of Utah wanted to determine if body shape influenced the tendency to fight or flee. For example, Olympic wrestlers tend to have a different body shape than Olympic runners. Would they be equally likely to choose fight and flight? And does greater strength come at the price of quick mobility?

To find out, they took a group of mice put them through a sort Olympics of their own. Over an 8-week study, they tested how males responded while fending off other males from an area containing female mice, as well as how they performed on treadmills before and after the exercise.

They discovered that the mice most likely to fight were the worst runners - they burned more oxygen while running. Mice who fled the scene when confronted were better runners, consuming less oxygen as they skittered along. The fighter mice were poor runners before and after the confrontation, while the runner mice trotted along more efficiently before and after the conflict. That seems to suggest that some of us are built for fighting while others are built for running away.

Getting back to our Olympians, does body type matter in our innate fight vs. flight ability? It doesn't seem so. Unlike the human Olympians, both running mice and fighting mice had about equal body mass. This points to physiological changes at play during when the mice sensed the threat.

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Is Human Survival Selfish? Fight Or Flight Explained

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