It means that every one of your ancestors successfully avoided death, at least for a while.

It also means that you come from a very long line of people who are good at being scared.

Lend me your ears, today we offer a tale of sound, science and fear. Welcome to the Sci-Fright Zone.

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In my video with "What's That Buzz?" we saw how easy it was to take something that's not normally that scary

and add a bit of fear using a few sound tricks.

Fans of scary movies know that there's primarily two ways that movies use sound to scare you.

The old jump out from behind a corner trick

or using sound to set a more generally frightful mood.

Sound is nothing but vibrations, what is it about our biology

that makes only some of them scary?

Now when I say "scary" I'm not talking about that creepy kind of scary

that grabs you, slowly

with its cold, ethereal hands.

[scary ghost voice]

That slow fear only happens when your higher

brain functions take over. The kind of fear I'm talking

about is instant fear. The fear that's built in

to your very biology.

Why do we get scared in the first place? Simple.

So you can live long enough to reproduce.

If you want to avoid being a lion's dinner,

you've got to think fast.

luckily sound moves faster than sight.

Now, light waves move about a million times faster than sound waves,

But a lot of your brain gets in the way first.

Think about what it takes to see something.

First light has to activate several kinds of

photoreceptor cells in your retina.

Then a signal travels down your optic nerve,

It stops in the center of your brain and gets sorted,

then it goes back here to your visual cortex

to be decoded, with the edges and the shapes,

Then it goes off elsewhere in your brain so you can

finally remember that the shape you're looking at is a lion.

All in all, that process could take up to

half a second. I don't know about you,

but when I'm staring down a hungry lion,

that's half a second too long.

This is why we say "we live in the past"

Like the train station in Hell, when it comes to what we see

we are forever delayed.

Whether it's optical illusions

or even just paying attention,

it's the very complexity of our visual system

that makes it so easy to fool.

But hearing operates on a completely different wavelength.

I love puns.

While you can shut off your vision pretty easily,

your sense of hearing is never really off.

Even when you're asleep.

You're just not conscious of everything that you're hearing.

Which is good, because otherwise

you would go completely NUTS.

In his book "The Universal Sense", Seth Horowitz

explains that hearing is a mechanical

rather than chemical sense. To demonstrate,

let's say I sneak up behind you.

[music playing]

[BANG!]

Between your inner ear and your muscles tensing

that signal only has to travel through 5 nerves.

The whole process is over before the rest of your brain

is even aware what happened.

You can't fight it, this is hard-wired

into your brain's anatomy.

This so-called "startle reflex" is probably

the fastest thought that you can have.

Of course startling us isn't the only way

that sound can make us feel things

beyond our conscious control.

Here's a famous example:

[dinosaur roar]

Now, we have no idea what a T. rex actually sounded like,

but for "Jurassic Park" they blended the sound of

a baby elephant, a growling tiger, and

an alligator's low-pitched snarl.

Using animal sounds to invoke terror

is one of the oldest tricks in the movie book.

[King Kong roar]

That's enough!

A 2010 study by researcher Daniel Blumstein

analyzed scary film soundtracks

and found that they contain more of what's called

"nonlinear sounds", which contain things like

rapid frequency jumps, nonstandard harmonies,

noise, or when an instrument or voice is

pushed beyond its normal range.

Animal alarm and danger calls seem to be full of

these nonlinear sounds.

It seems to trigger some sort of innate danger signal

inside of our brains.

They've even incorporated these nonlinear sounds into film music.

Which I can't play for you because of intellectual property law.

But I put a bunch of links down below,

so make sure to check these out.

In Alfred Hitchcock's "The Birds"

Oskar Sala made nonlinear bird noises

using an instrument called a trautonium.

Stanley Kubrick's "The Shining" owes its

super-creepy nonlinear soundtrack to

Polish composer Krzysztof Penderecki.

And in "The Day The Earth Stood Still"

Bernard Herrmann used what is probably

the most nonlinear instrument of all time, the theremin.

[theremin playing]

The list goes on and on. No one knows if

these composers consciously added

nonlinear sounds to their music,

but the effect on the audience is unmistakable.

Our brains evolved to be scared by that.

We've seen how movies use sound to scare us to death.

But our brains are really scaring us to life.

So go enjoy that scary movie, just remember:

Even if you close your eyes, you can't escape

The Sci-Fright Zone.

Head on over to "What's That Buzz?"

to watch our super-scary cat video.

If you'd like to watch something a little less frightening

then subscribe to this channel.

Stay curious.

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