Asked by: Anonymous
This instinctive reaction is called the acoustic startle-reflex eye blink and is part of the protective mechanism we all show in response to potential danger. Loud noises can often mean danger and our eyes need protecting more than most parts of our bodies.
This blinking happens faster and harder when people are frightened: for example, when they are told they are about to get an electric shock, even if they don’t get one. Darkness makes the blinks larger and this effect is even greater in people who are afraid of the dark.
Feeling happy and relaxed decreases the response, while trauma increases it. For example, exaggerated startle reflexes have been measured in people suffering from post-traumatic stress, including veterans of the Vietnam and Gulf wars. Alcohol decreases the effect, while amphetamines increase it.