♪♪ -When you think of the senses, you probably think of five different ones.

Six, if you're into that.

♪♪ Sight... sound... taste, touch... and smell.

They are the building blocks of experience, of creativity, of happiness, even.

And for some reason, we like to separate them.

♪♪ Seeing a sunset versus tasting a ripe peach -- equally inspiring, but totally different.

Right?

Well, not exactly.

♪♪ The body is actually like a sponge, constantly absorbing all these sensations from the world around us.

[ Trilling ] And as they enter through our eyes, ears, skin, they begin to swirl together.

What emerges is our own unique picture of reality, one that we become completely immersed in.

♪♪ ♪♪ ♪♪ ♪♪ -When we're going out there on the ice and Tarah's 8 feet above my head, you have to start to learn to use another sense of being able to know where your partner's going to be.

♪♪ -I am so focused on the task at hand and what is in front of me at exactly that moment that nothing else matters.

-My name is Tarah Kayne.

-And I'm Danny O'Shea.

-And we are pairs figure skaters who train in Colorado Springs.

♪♪ We have been skating together for eight years.

-Danny and Tarah are at the top of their game, national champions and real contenders for the next Olympics... ♪♪ ...which means they can do crazy stunts in perfect unison... ♪♪ ...like clockwork.

And performing at that level requires tapping into all the senses and then some.

-Before the competition, I make myself thoroughly aware of the rink.

I see the whole rink and I smell what the rink smells like, I feel how cold it's going to be there.

-Our senses all interact with each other.

Our sensory system is a very complex system that allows the environmental stimuli to be converted into electrical activity that our brain and our spinal cord can process.

♪♪ -On every cell of our body, we maintain a little battery, which has a voltage.

-In our fingertips, in our eyes, and our ears, we have the ability to sense small changes in our environment that create small changes of voltage.

A bigger change in the sensed world creates a bigger change across that cell membrane.

That is something that's really good for sensation.

♪♪ -So, for example, the sound of a blade cutting through the ice... [ Sharp crack ] ...becomes electricity.

♪♪ Specialized cells called neurons transmit that information to the brain... ♪♪ ...which instantly combines it with other data, like the rush of cold air... [ Whooshing ] ...and the blur of limbs as the skaters move together across the rink.

♪♪ This all happens while they are spinning, jumping, and landing on a piece of metal that's only 5 millimeters thick.

♪♪ -Pairs figure skating is definitely dangerous.

♪♪ You're skating on a very hard surface.

[ Blades clack ] We have blades on the end of our feet.

-Some of the major elements in pair skating is first the lift.

She's either upright or on her stomach or on her back.

We have three and a half turns in our lifts.

♪♪ Then you have your jumps next to each other and landing in unison.

Then you have your throw into the air.

She does the hard part, rotates and lands.

We have spins connected or side by side, spinning in one spot on the ice.

Death spiral is another one.

♪♪ I put my toe pick in the ice and do a pivot... ♪♪ ...and she holds my hand and she spins around me for a couple revolutions.

♪♪ -When I'm on the ice, it's just focus.

♪♪ When we change venues, the colors are all different and all the sides of the rink look the same, so I don't really have any visual points of reference.

♪♪ -Our previous experience always adds onto our sensory experience.

This information has to quickly integrate with all the other senses.

-The performance becomes so routine, and the senses are like us doing the elements and feeling the elements... -Yeah.

-...instead of thinking through the elements.

♪♪ -I have to know by how I feel in the air.

A lot of times we practice with my eyes closed so that I don't get confused, and then I try to come out of the air at the wrong point and that can get dangerous.

♪♪ -At the speeds Danny and Tarah are moving, five senses just won't cut it.

♪♪ So they rely on something even more fundamental.

Some people call it the sixth sense, but it could just as easily be called the first -- proprioception.

In simple terms, the sense of where your body is in space.

-So you can imagine there's a two-way highway of signals that constantly reaches areas of your body that are far away from the brain.

Those areas actually tell something about the status of your body to the brain.

-Wrapped around specialized fibers inside every muscle are tiny springs that stretch when we move.

The precise direction and speed of that motion activate receptors in the spring that create an electrical signal.

-Those receptors send that information to different parts of the brain.

When the brain processes that, it sends information back -- for example, our motor nerves, to say, "Move your hand."

♪♪ -All of us use this sense constantly.

♪♪ Without it, you wouldn't be able to pick up a glass or touch your nose in the dark.

But on the ice, it's critical for knowing when to stop rotating, or where to place your blade so it doesn't nick your partner.

And yet, for pairs skaters, there's still one more challenge.

And it is the most elusive.

-We have to have such synchronization and unison.

♪♪ -You need to have chemistry together as a team.

And physically, your bodies need to match.

♪♪ At this point in time, I know every tap... ♪♪ ...every squeeze.

I know almost what he's going to do before he does it.

When we're doing lifts, Danny will just slightly grip my body in a way that communicates to me that it's time for me to change positions.

And we've never even discussed that.

♪♪ -The synergy that Danny and Tarah have created over years of training has a lot to do with touch, and its unique ability to deepen a physical connection.

♪♪ -We have the mechanical receptors in our skin for physical touch, and that information that's converted to electrical activity ultimately feeds through our spinal cord and gets to parts in our brain that senses that that was a mechanical touch.

♪♪ However, the signal also goes to other parts of our brain... ♪♪ ...that encode an emotional aspect to that touch.

And the brain can dissociate a mechanical touch and the emotional connectivity of that touch.

♪♪ -This duality helps us sense the difference between a hug and pinch.

But there are many more layers of subtlety touch can uncover.

All it takes is the dedication to learn them.

-We've worked a very long time to have that second nature thing where I can put my hand out and she can just grab it, and we're together.

♪♪ -There's no doubt that emotions depend on touch.

There's a reason they're called feelings.

♪♪ But all of our senses can create emotional responses.

And it has to do with how different parts of the brain speak to each other.

[ Cheering ] ♪♪ -We're starting to finally get a glimpse into the inner workings of the brain.

A really interesting field called optogenetics has been able to help us study the brain by getting parts of it to light up as it's functioning.

And so we're starting to get a sense of how is it that the cells of the brain can craft our emotional experience of the world.

♪♪ -One of the most potent emotional triggers is smell.

♪♪ ♪♪ Like dreams, smells have the ability to reveal things that are buried deep in the unconscious mind.

But it happens while you're awake.

-Fragrance allows you to armchair travel.

♪♪ What's great about using materials like cilantro from Mexico or Italian parsley... ♪♪ ...you can go to a place through the voyage of olfaction.

[ Sniffs ] ♪♪ They spray that fragrance around them, and then they think, "Oh, my God, I'm suddenly on a beach in Indonesia.

I'm in Thailand."

♪♪ And that feeling of giving someone that ability to travel momentarily to that place is something so powerful and so potent.

♪♪ I'm Yosh Han, and I create fragrances for a living.

♪♪ -There's some senses that are much more powerful.

Smell actually is a very powerful sense.

♪♪ -We used to think that humans could only detect about 10,000 distinct smells.

Turns out, that number is actually closer to a trillion.

♪♪ And it all starts with tiny hairs.

Smells, as we know them, don't really exist.

At first, they're just pieces of air, molecules that waft into the nose.

-Inside our nose we have cells called cilia.

They're made of the same thing that makes your hair.

These cilia have the ability to pick up these molecules that are around us.

-The cilia direct air molecules to receptors underneath the lining of the nostril.

There are around 400 kinds of receptors that pick up different scents, and the same receptor can be activated by more than one odor -- like a lock that has 10 different keys.

♪♪ Whatever you're smelling lights up a unique pattern of receptors, and they send impulses to the brain.

Think about the smell of coffee.

It's actually made up of 800 different molecules.

It's only when this complex mosaic of signals reaches the brain that a smell as we know it comes into being.

♪♪ -I don't actually necessarily sit in a lab with a white lab coat.

That's just not my forte.

Rather, what I do is a much more creative approach.

What I like to do is think about using the olfactive materials as kind of like paint or an instrument, if you were a musician.

♪♪ Some people smell in numbers, some people smell in colors, and I have more that smell in textures.

I smell scratchy things.

I smell smooth things.

I view olfaction as a narrative.

I view ingredients as characters, and so I'm constantly composing in my mind.

♪♪ -Being a perfumer requires some serious training.

Smell is 10,000 times more sensitive than any other sense.

So a professional like Yosh hones that over time, and in the process, learns how to tap into the strong associations that smells create in the brain.

♪♪ -The sense of smell is the strange guy in neuroscience.

If you look at how the sense of smell works, we can identify a variety of things that are actually only specific for the olfactory system.

Even the brain regions to which our olfactory system connects are very different than the other senses.

-Most of our senses are processed by a part of the brain called the thalamus.

♪♪ The thalamus is like a switchboard, relaying those sensory signals to other parts of the brain.

♪♪ But for reasons that we're still trying to uncover, our smell signals initially bypass the thalamus altogether and head straight to the olfactory bulb... ♪♪ ...which connects to other, older regions that are responsible for emotion.

♪♪ This gives smell a special ability to create feelings on a subconscious level.

♪♪ [ Door opens ] -Hi.

-Hey!

-How are you?

-Good.

-I'm Yosh.

-Yosh.

I'm Sean.

-Sean.

-Nice to meet you.

-Welcome.

-How are you doing?

-Good.

I make fragrances for myself, I design fragrances for myself, but I also spend a fair amount of time creating custom fragrances for individuals.

Do you like wearing fragrance?

-I don't know.

This is an interesting gift.

[ Laughs ] -Oh, perfect.

Perfect.

I'll do a little intake for him, because I really want to know, what does he like to eat?

What does he like to do on his off time?

Where did you grow up?

-I grew up in Hawaii.

-Hawaii.

So, like, you've grown up with salt, the waves, and maybe some tropical fruits.

We have so many materials that we can choose from.

So I'll show him a range.

What I'm looking for is if someone really loves the smell of something, their whole body just lifts up, and that's really what we're trying to capture in a custom fragrance.

-It's a Mojito.

[ Sniffs ] -Yum, okay.

And you like cocktails?

-Love cocktails.

-[ Laughs ] -Yeah.

-So let's move into the fruit notes.

What looks good to you?

-Number one, I would go to the mango, then I would go to the pear.

I would've went to the guava third.

-Okay, guava third.

-Mango, number one.

-Okay, that's good to know.

♪♪ -Smells are visceral.

We love some.

-[ Sniffs ] -We hate others.

And this immediate connection between smell and emotion points to our evolution as a species.

At first, we needed sensitive noses to survive.

And that is reflected in the brain.

-The olfactory system directly speaks to what we called high-level regions, like the amygdala, related to the perception of threats.

♪♪ -Our amygdala is able to look at the outside world and put it into an emotional context, and then communicate with other parts of your brain which will help you decide, "Hey, you're in a safe environment.

Don't be afraid."

-It's a little bit primal.

That's how it originally was experienced.

And I think over millennia, it went from you smell death, you smell a winner, you smell a rat, and then it became more of a pleasure-seeking way to navigate in the world.

We're gonna do top notes, middle notes, and base notes.

-Okay.

-We're gonna start with the green notes, or the top notes, okay?

Okay.

Smell that and tell me... -That's gonna be -- [ Sniffs ] Yeah.

This right here is -- that's an 8.

-What about cucumber?

-This is going to be a 10.

I'll tell you right now.

-With perfumes, you can really access someone's subconscious and their inner deep emotions.

How we think, how we feel.

♪♪ You can imagine a vista, a landscape, especially, of a certain place.

But what if that place is an emotional place, or personal space?

I can bring them from the past into the present or into the future.

♪♪ I'm going to actually have you smell some flowers.

You mentioned that you were from Hawaii.

-Mm-hmm.

[ Sniffs ] Oh, this reminds me of my auntie.

♪♪ I just got goose bumps, like, like this is a pretty serious thing.

She passed away about eight years ago from cancer and she was my -- she was like my mom.

♪♪ [ Sniffs ] I haven't thought about her in a while.

It's, um... it's pretty heavy.

-Part of the network that smell moves through is not just instinct and feeling, but a connection to the past.

-[ Sniffs ] -And that's the power of fragrance, right?

-Yeah.

♪♪ -The brain keeps all of these memories, and you think that they're gone.

And something happens in the environment, and it triggers that memory, and you can actually smell something from when you were a child.

All of the memories associated with that initial odor, whether it's good or bad, are released, and a lot of that is because of the amygdala.

It stores not only negative, but also positive, memories.

♪♪ -So for your final creation, we have some oud.

We also have salt.

And then we have waves.

Combined together, we have Ride the Wave.

-Excellent.

That's impressive.

-[ Laughs ] At the end of the day, they want the smell of home.

"This smells like me."

♪♪ They want to feel like they're really in their skin.

Fragrance allows me to tap into that in a way that no other thing really does.

♪♪ ♪♪ -Even as the brain changes, memories of smells remain etched in our minds.

♪♪ Things we've seen?

Those memories can fade after just a few hours.

And yet, sight is the primary sense we use to navigate through the world.

-We have a much better sense of sight than many other organisms out there do.

We see a wider range of color, our vision is more acute, and we have depth perception.

It may be that we all have sort of this ancient programming to respond to images.

♪♪ -80% of our reality comes from vision.

So even though it's not as immediate as other sensations, it could be considered the most important.

Which means that for us, almost nothing is more disorienting... than finding yourself total darkness.

♪♪ And yet, it's in the moments that test us most when the true power of sensation emerges.

♪♪ -Here on Vancouver Island, there's a myriad of textures... ♪♪ ...colors.

You see it on the reddish, brownish bark of the Arbutus tree.

♪♪ All the green and many colors on the flowers.

♪♪ And then just feeling a breeze off of the ocean.

Fresh air out for a hike, lots of space, lots of freedom, and you sense these things in different ways above ground.

[ Birds chirping ] This is where humans are meant to be.

But when you go below ground, there are things down there telling you that you don't really belong there.

♪♪ -Keep breathing!

Hands out!

Come towards me!

Come this way!

Stay up!

Come on, Jason.

♪♪ -My name is Jason Storie, I'm an amateur caver, and I live in British Columbia, Canada.

When you go into a cave, there's a certain smell.

It's kind of earthy and damp, and everything's quiet.

[ Water dripping ] The darkness is so absolute.

It's hard to explain to anyone who's never experienced it.

You might have a very good headlamp, but... it only lets you see so far ahead.

Darkness is still around the corner.

♪♪ You just never know what you're going to find.

♪♪ -Caves have always been dangerous places to explore.

One wrong turn, and you could be lost for days... or forever.

But when you take that first step into the void, you're actually way better equipped than you might think.

-One of the most remarkable things of our visual system is that our retina is actually able to perform two different things at the same time.

♪♪ One group of cells called the cones actually activates in presence of light and color.

But there is another type of cell.

These are called the rods, which actually are specific for situations in which there is way less light.

♪♪ These rods provide a vision that is more black and white, but still allows you to perceive certain spatial relationships.

For example, you will be able to identify certain sharp objects around you.

You can just imagine walking inside a cave in which you don't have light available.

You are in complete darkness.

And in these kinds of scenarios, we actually are remarkably good at seeing things.

♪♪ -When you go into a cave and everything's unknown, you don't know what's around the next corner.

There's even the possibility that you might discover something in a cave that someone just hasn't gone and dug out that one little corner.

-The transition to night vision isn't immediate.

It takes about 30 minutes for the retina to adjust to darkness, so something else happens even faster.

-The brain is like a computer and a movie projector all at the same time.

And like any other living system, it's very adaptable.

♪♪ -The brain is fascinating when it's put in a situation where it can't see.

You're put in pitch black, and before your visual receptors can start to acclimate, the brain starts to put its own images of where things should be.

♪♪ -Groups of specialized cells deep within the brain record distance... location... direction, and speed.

They light up as we move around and become projections that help us navigate our environment.

Like an internal GPS.

But caves are still notoriously difficult to chart.

♪♪ -Andrew Munoz is a caving expert.

He was the one who got me into caving.

We had become good friends.

-Show me what I'm doing.

-So I think we'll just get you to find the wall, and we'll just have this on as your backup.

-Yeah.

-And on December 5th, 2015, Andrew and I and three others went caving.

I had been in Cascade Cave five weeks earlier with Andrew, and it was definitely the toughest cave I'd been in.

Awesome!

It involved some very tight squeezes, places where you have to sort of go on your back, upside down, and worm your way through to the next passage.

♪♪ ♪♪ You have caves that have water systems in them.

You'll get drips or trickles or even waterfalls that can be a little more thunderous.

[ Water crashing ] You can be in one passage and hear thunderous water roaring nearby, and then within 90 seconds have crawled through a tunnel and be in a big open chamber, and there's complete silence.

[ Wind whistling ] [ Thunder crashing ] [ Thunder rumbling ] We maybe didn't quite read all of the signs that the water level was on the rise, and that storm of the year was brewing outside.

-[ Bleep ] -Stop!

[ Bleep ] That's [bleep] awful.

-I got a little bit confused about which direction I was supposed to go in.

-So I turned around and went back down the tunnel to go and ask for directions.

And that's when everything went sideways.

-Okay, okay, just relax.

Just relax, J.

His head up?

His head still up?

-[ Shouts ] -Yeah?

-I got stuck in the tunnel, like a cork in a bottle.

-A few wrong moves left Jason in the midst of sensory chaos that was about to push his brain and body to the limit.

-Don't make any fast moves, okay, J?

You have to keep your head up.

-Yes.

-And we're going to do this slowly, okay?

-My helmet was against the ceiling.

Water was coming up over my shoulders and over my ears.

-Not much left.

-It's in my ears -Keep coming, dude.

This way, towards me.

-The air around my face and around my mouth was only about an inch.

-Keep coming, dude.

You're not stuck.

You're not stuck.

-I had the combination of sensory deprivation and sensory overload all at once.

With the sound of the water basically drowning out everything, with our headlamps off, I had no sight and no hearing of anything apart from the canons of water.

[ Water rushing ] -That's you?

-Jason was experiencing a two-pronged assault on his senses.

First, by entering the darkness of the cave at all.

Then, by getting trapped in the flooding passage.

-You got good hands?

-Yeah.

-Talk to me, dude.

You got good hands?

-Yes.

-Okay.

Lift your hands up and [bleep] float, Jase.

Come on.

Try!

[ Bleep ] Okay?

Dude, [bleep].

Jase?

[Bleep] look at me, okay?

You made it, all right?

-Yep.

-It's scary.

You made it, okay?

-As soon as Andrew had gotten me through and we'd gotten our legs untangled and I was sort of free, I felt like, "Yes, I've made it out.

He's saved my life and now we're going to get out of the cave."

But everything slowed down.

♪♪ We were trapped for about 12 hours.

-Andrew managed to free Jason from the direct path of the water pouring in from the storm above.

But the flooded tunnels made an escape impossible for the team.

-I knew something was wrong because when I went to speak, my speech was slurred.

-My left leg is... -It's okay, I'm gonna move you.

Don't move, okay?

Just relax.

-I definitely had stage 1 hypothermia.

The sound of the roaring water would cause slight sort of auditory hallucinations.

-[ Eerie voices whispering ] -I would think that I could hear voices in the water.

-[ Eerie voices whispering ] ♪♪ -When it's overwhelmed, the brain's power can become debilitating.

If sensory inputs are out of whack... -Go.

-...the brain goes haywire trying to piece things together.

You might end up experiencing things that are outside reality, like phantom sounds.

And when that happens, the only thing left to do is try to take in less information.

♪♪ -Lying there, trapped and cold and shivering uncontrollably, I knew I had to do something.

♪♪ So I turned to deep breathing meditation.

♪♪ I pulled my sweatshirt up over my head and I took deep, deep, long breaths.

♪♪ -In the past 10 years, we started studying meditation as a way to understand what happens when you direct all your resources towards something that is as internally generated as possible.

The first rule of meditating is to somehow try not to process anything that comes from the outside.

-And I concentrated.

I really focused on each and every breath.

When I exhaled, I found I could try to stave off the shivers by focusing on what my chest and chin could sense instead of what the rest of my body could sense.

♪♪ There's a lot the brain can be trained to do.

Being able to control our thoughts can even help us with things like chronic pain and suffering.

That's really the best way for us to manage stress and for our brains to function optimally.

-Ironically, Jason's survival instinct was to detach himself completely from his environment.

♪♪ To try to cut off all of his senses, and turn inward.

And in the end, that might've been what saved him.

-Keep fighting.

-At about 3:00 in the morning, the water was starting to recede.

It was sort of now or never, and I knew this was our chance.

♪♪ Andrew went through first, and then he sort of guided me through the tunnel.

-[ Groans ] -There was a tight squeeze to get through to the next sort of big, open chamber.

We made it through.

That was the point where we saw lights coming down from above, and I could hear voices.

-Hello?

-I love you!

-Ha ha!

-Oh, my God!

-I was very, very grateful that they were there to -- to pull us out.

♪♪ Search and rescue medics checked us over and told us that we were fine.

And then it was sort of over, which was surreal.

My senses were definitely having a hard time computing that this world existed and is normal.

♪♪ I had to sort of pinch myself to believe that, yes, we had made it out.

And here I was standing amongst the everyday chatter that your ears normally take for granted.

♪♪ -The sensory blackout Jason lived through was terrifying but temporary.

♪♪ Sometimes it's more permanent.

Like a condition called anosmia, or smell blindness.

But for people whose senses are reduced, the drive to adapt is even stronger.

-We as a species are constantly evolving in diverse environments around the world.

♪♪ There's a whole island of people in Polynesia, and there's a really high incidence of people who don't see color.

♪♪ What they do see is a whole lot of texture that a lot of "normally sighted" people don't see.

♪♪ So you could argue in an environment rich with flora and fauna, the ability to see and discern the differences of different plants that emerge when you can see these different textures... what's an ability, and what's a disability?

♪♪ -The genius of human sensation is that it learns with us, especially when we figure out how to harness it in an entirely new way.

♪♪ -Sound is a beautiful thing that I think we don't pay enough attention to.

♪♪ The body is basically a water bottle.

♪♪ And all of these vibrations are smacking into your system and leaving imprints everywhere.

♪♪ I like to feel the world around me.

♪♪ [ Kick drum beating ] -♪ And as I saw the sky I wish the clouds ♪ ♪ Could catch me ♪ ♪ So I could stay up high and view the world ♪ ♪ From above ♪ ♪♪ My name is Mandy Harvey.

I am a singer-songwriter.

I happen to be deaf.

♪♪ ♪ Pray to be ♪ ♪ Just sleep ♪ ♪ And it won't ♪ ♪♪ -So the sights, sounds, and feelings we encounter are absorbed by our cells in exactly the same way.

♪♪ It's all electricity.

[ Electricity crackling ] And if that is true, couldn't we experience the same stimulus in more than one way?

♪♪ -I was born with hearing issues.

Throughout my childhood, it was a very tumultuous experience.

There were constant infections and surgeries, and there was almost a full year where my eardrums would just stop vibrating.

[ Echoing drum beat ] ♪♪ And it just kept getting worse and worse and worse.

I realized that no matter what was going to happen, it was not going to be what I thought it was going to be.

♪♪ But music was always the passion and the love, so there was this mix of, this is my reality, but this is what I want to do with my life.

-It's really interesting to me how adaptive we are as humans.

♪♪ When we have a reduction of sensory input and what that means in terms of neuroplasticity and how our other senses give us even more nuance.

♪♪ A single base pair deletion on your DNA could mean boom.

♪♪ You're going to lose your vision in the course of a lifetime.

And yet vision, it's just another input.

♪♪ And we as humans can adapt to all kinds of things.

♪♪ -When you lose a sense, everybody says that your other ones heighten.

I don't really feel that that's true.

I think you just start paying attention to them more.

♪♪ I started paying attention to other things to support my dream.

♪♪ At the very beginning, I would hold the balloon and talk or play the radio next to it and feel all of the vibrations elevated through this conduit balloon.

♪♪ ♪ And I fall ♪ ♪ Again ♪ ♪ I fall ♪ ♪ Again ♪ ♪♪ You can feel the difference from your own voice compared to like a really bass-y guy talking at the same time.

And it's just a way for you to be able to shut off your brain of what it's supposed to be.

♪♪ ♪ I fall ♪ ♪ Again ♪ ♪♪ -I think we're also learning quite a lot about the ability of our minds to adapt to the information input that may be shifting over time.

♪♪ We've seen, for example, with folks who are blindfolded for a period of days, that their brain's ability to transduce sound becomes enhanced.

♪♪ -The more that we consciously tap into alternative ways of experiencing sensation, the better our brains get at interpreting that sensation -- and using it.

In the case of music, though, there are many different levels to harness, and not all of them are as simple as holding a balloon.

-[ Vocalizing ] With singing and not being able to hear yourself, the part that's difficult is pitch.

[ Vocalizing ] What I do now is sit in front of a mirror and put my hand on my throat with a visual tuner, find a note, and then feel where those vibrations are the strongest.

It's actually here today.

It moved.

And then draw a line or shape based off of the texture and then the note to dictate it.

[ Vocalizing ] And there's a little tickle over here as well.

♪♪ This one is D, but it feels like it rotates.

I kind of ground myself moving up and down the scale, marking from about here to sometimes all over my face.

The E feels like it's bouncing in two different places and kind of washing over at this whole side.

Where those notes tickle or rumble or have like a gummy, weird feeling -- there's so many different things back and forth that create the whole picture.

Middle C, it's always, for me, a feeling around my neck, right up this crease.

♪ Ooh ♪ And then when I'm writing songs, if it's something that causes me an annoyance or a frustration, I'll put that note specifically in a song that's about frustration or angst or falling.

♪ I know I'm falling again ♪ ♪ I see the ground ♪ ♪ Approaching ♪ I'm not trying to create a new wheel.

It's already there.

♪ Maybe if I close my eyes ♪ ♪ I will fly away ♪ I just need to take the pieces apart to paint it out so I know exactly what's happening.

♪ All ♪ ♪ A dream ♪ ♪♪ -Most human languages rely primarily on the production of sound, so obviously hearing is important in that sense.

♪♪ In terms of whether we're particularly good at hearing things compared to how good our visual system is, is interesting because it's relatively weak, while our visual system is quite strong.

There are many other ways to communicate, and obviously we use body language.

♪♪ -When I'm playing on stage, there's so many things that are happening at the same time.

You're looking for the head nod from whoever's playing the rhythm.

You're looking at their faces when one person's taking the lead.

♪♪ You have bare feet on hard floor so that you can feel the rhythms of what's going on around you.

♪♪ It feels a lot like kind of like we're dancing.

♪♪ The weird thing for me now is that everything vibrates... [ Echoing rumble ] ...and it can be very exhausting.

Every once in a while, you just want to shut it off and just be numb for a little bit, to close your eyes and sleep and just breathe.

♪♪ I have this beautiful hanging chair.

♪♪ It just kind of shuts off the ability to feel so much.

♪♪ You get the movement and the feeling of the wind.

♪♪ I like to write in that chair because I'm more focused on the calm, and it allows my brain to just go.

♪♪ -So it's not about only processing the environmental stimuli and helping us to navigate through our world.

The individuality of the brain and the creativity of the brain is profound.

But it's not equal.

Each of us have different levels of creativity.

♪♪ ♪♪ -Experiencing my own music without being able to hear it is different than what I imagined it would have been, but it's beautiful in its own way.

♪ I know I'm falling again ♪ ♪ I see the ground ♪ ♪ Approaching ♪ A lot of people expect that I should be sad that I can't hear how beautiful my voice is.

♪ And as I peek ♪ ♪ I scream aloud ♪ Who cares?

I get to feel what's happening and I'm paying attention to things that you ignore.

♪ I fall ♪ ♪ Again ♪ ♪ I fall ♪ ♪ Again ♪ ♪ Fool-heartedly ♪ ♪♪ So in my eyes, I feel bad for you for not being able to experience music in this way.

♪♪ -The human capacity to experience the world in infinitely diverse ways is astounding.

♪♪ And it's not only a testament to sensation, but to our profound creativity as a species.

-It's not just the five senses.

It's not just a real world that's out there.

Our brains actually create things.

That aspect of creativity makes each of us individuals, and therefore very special.

♪♪ -Molecules... and light... and vibrations... [ Rumbling ] ♪♪ ...become memories... and thoughts... and inventions.

♪♪ Not only do our senses define our reality... ♪♪ but they help us create entirely new worlds... ♪♪ ...all the time.

♪♪ ♪♪ -To order "Human: The World Within" on DVD, visit shopPBS.org or call 1-800-PLAY-PBS.

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