Why Do We Blink When We Hear a Sudden, Loud Noise?

The reason we blink when we hear a sudden, loud noise is because it is an involuntary response. Our bodies are programmed to react this way in order to protect us from potential danger. When we hear a loud noise, our brain kicks into defense mode and releases adrenaline, which prepares us to deal with the situation at hand. The main components of the brain that are involved in this reflex reaction are the amygdala, hippocampus, and anterior cingulate cortex.

You have probably experienced this many times; you are sitting in the safe confines of your house, keeping your smartphone company, when suddenly there is a loud bang that makes you jump. Not only do you jump, but your eyes snap shut immediately!

You can see this in movies too. Even when the hero is expected to be a tough guy, he blinks and squeezes his eyes shut just like a scared child when he fires a weapon (which produces a loud noise).

Why is it that sudden, loud noises make us blink?


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An Involuntary Response

The first thing that you should know (and many of you must already know this) is that blinking your eyes at the sound of a loud noise is completely involuntary, meaning that you don’t have any control over it. In other words, there is no point in ‘making sure’ that you don’t blink next time you hear a cat meow a bit too loud from over your shoulder.

Humans have evolved in a way that has guaranteed their survival in different situations and this is something that we should be very happy about. Therefore, when the human body feels that it’s in danger, it releases adrenaline, the famous fight-or-flight hormone, which equips it with the necessary energy to deal with the situation at hand.

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Since our body associates a sudden, loud noise with danger (in ancient times, loud noises were mainly associated with a wild beast or some natural calamity), it kicks into defense mode to save itself from any dangers coming its way.

Startle Response

The instinctive reaction of the human body, when faced with potentially dangerous situations, is called acoustic startle-reflex eye blink. The startle reflex is a reaction that is triggered by the brain in order to protect the back of the neck (whole-body startle) or eyes (blinking of the eyes).

The acoustic startle-reflex eye blink is found to be caused by sudden sounds that are more than 80 Decibels. The main components of the brain that are involved in this reflex reaction are the amygdala, hippocampus, and anterior cingulate cortex.

brain insides
It is interesting to note that the anterior cingulate cortex in the brain is known to be directly associated with our emotional response and awareness. This means that this part is also the one which hugely determines how an individual reacts to a startle-inducing stimulus (in this case, a loud noise).

This is a tremendous defense mechanism. By getting you startled, your brain makes sure that you are ready and aware of your surroundings before you even identify the source of the noise. This reaction means that you are ready to deal with any situations that may arise following the noise. Well done, brain!

It Depends on the Individual

How a person reacts to the same stimulus largely varies from one person to another. People who are stressed or depressed are more likely to blink faster and harder (along with producing a loud scream). This effect is accentuated when the individual is in the dark, as the individual is even less aware of his or her surroundings through the visual means. This means that you will shut your eyes harder if you’re in a dark room, as compared to a well-lit room when you hear a loud noise. Patients suffering from post-traumatic stress, including war veterans, have an exaggerated startle.

Being happy or relaxed eases you and therefore decreases the magnitude of your startle-reflex. Also, alcohol reduces your reaction too.

Now that you know the truth, don’t be embarrassed next time you shut your eyes when someone switches on their television to a loud action film!

Also, don’t be embarrassed when you get scared like this…

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References
  1. Science Focus
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About the Author

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spearheads the content and editorial wing of ScienceABC and manages its official Youtube channel. He’s a Harry Potter fan and tries, in vain, to use spells and charms (Accio! [insert object name]) in real life to get things done. He totally gets why JRR Tolkien would create, from scratch, a language spoken by elves, and tries to bring the same passion in everything he does. A big admirer of Richard Feynman and Nikola Tesla, he obsesses over how thoroughly science dictates every aspect of life… in this universe, at least.

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