War

by Sebastian Junger

Humans evolved in a world where nothing moved two thousand miles an hour, so there was no reason for the body to be able to counter that threat, but the brain still had to stay ahead of the game. Neurological processes in one of the most primitive parts of the brain, the amygdala, happen so fast that one could say they compete with bullets. The amygdala can process an auditory signal in fifteen milliseconds—about the amount of time it takes a bullet to go thirty feet. The amygdala is fast but very limited; all it can do is trigger a reflex and wait for the conscious mind to catch up. That reaction is called the startle, and it is composed of protective moves that would be a good idea in almost any situation. When something scary and unexpected happens, every person does exactly the same thing: they blink, crouch, bend their arms, and clench their fists. The face also sets itself into what is known as a “fear grimace”: the pupils dilate, the eyes widen, the brow goes up, and the mouth pulls back and down. Make that expression in front of a mirror and see not only how instantly recognizable it is, but also how it seems to actually produce a sense of fear. It’s as if the neural pathways flow in both directions, so the expression triggers fear as well as being triggered by it.