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What is the mechanism behind fear?
Answer 1:

Emotions, such as fear, are psychological “programs” that involve all parts of the brain to come up with a response that is appropriate to the situation. First a threat must be perceived, for instance seeing a spider. This then triggers a part of the brain called the amygdala, which is responsible for sending signals all over the brain and body to deal with the threat. For example your heart and breathing rates might be ordered to go up, providing more energy to your muscles; digestion of food might be ordered to slow down; and your pupils might dilate; and many other responses. This then creates your sense of fear. Should the threat be severe it might trigger the flight or fight response, where you will do whatever it takes to run or fight for your life. Intense fear may result in post-traumatic stress disorder, where people suffer powerful feelings of fear at inappropriate times.

It’s interesting to note that what we fear seems related to threats that have been with us long before we lived in the modern world. This is called an evolutionary mismatch. For instance people are far more afraid of spiders than electrical outlets, but the latter hurt far more people. It might be the case that our brains do not see the dangerous parts of the modern world as threats.

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