Some reflexes cannot be entirely overridden, of course. The human startle response, for example, is something we possess from the womb. The first 150 milliseconds of the startle response begin with a very small but reliable reaction. We blink. Like almost all of the fear responses, blinking serves a useful purpose—by potentially protecting our eyes from harm. (In laboratory experiments, people blink even more rapidly when they see unpleasant images.) Meanwhile, our head and upper body automatically lean forward, and the arms bend at the elbow—positioning the body to fight, cower, or flee.
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