- Hey, Smart people.

Joe, here.

This is a video about the strange way that some people experience reality.

If I were to ask you what color is the letter A, what would you say?

This is what some neuroscientists wondered in 2013.

They asked study subjects to assign a color to every letter of the alphabet.

Now, without talking to one another, participants overwhelmingly agreed that A's were red and so were S's, but U's were yellow and W's were definitely blue.

The scientists were shocked.

The odds that people would agree on this many same letter color combinations by chance was less than one in a billion.

So, what the heck happened here?

Well, the answer may lie in a children's toy.

In the '70s and '80s, if you looked at the refrigerator in an American home, you might see a set of these magnetic letters.

While most of us were spelling words like cat and I don't know, uncopyrightable, other people's brains were making strange technicolor connections that would last the rest of their lives.

See, the people in this study, the ones who showed a shared association between letters and colors, all had a condition called synesthesia that causes people's senses to get tangled up and blended together.

So for participants in the letter study, seeing a specific letter involuntarily triggered another sense, like color.

About one in 25 people have some form of synesthesia.

Some of the world's greatest thinkers, like Nicola Tesla and physicist Richard Feynman had synesthesia.

As do many creative artists like Olivia Rodrigo, Billie Eilish, and Beyonce.

But for those of us who do not experience synesthesia, this can be really difficult to understand or even imagine.

And it got me thinking, why do some people end up with blended senses, but most of us don't?

Today, we're gonna learn what synesthesia is, how it works in the brain, and why some people end up thinking Friday is purple while most of us don't.

(upbeat music) Attaching words to the sensation of color is known as grapheme-color synesthesia.

It's the most common type.

In fact, about 25% of people who have synesthesia have their letters connected to their colors.

But scientists have identified more than 150 different types, all of which combine senses in different ways.

For example, some people hear sounds that make them feel physical sensations, like heat or pain.

Others see colors when they hear specific music, and some synesthetes can see someone touching a person or an object and feel like they're touching it too.

And you're not limited to just one set of connections.

Some people have multiple types of synesthesia that combine and overlap.

But how does a person acquire these super sensory powers?

Scientists suspect whether you end up having synesthesia or not has a lot to do with how your brain develops as a kid.

As all humans learn and grow after birth, the neurons in our brains start connecting with one another.

And when they do, they form a synapse, which is like an information intersection.

Synapses allow electrical signals to pass from one neuron to the next, and the next, and the next forming networks that create our conscious and unconscious experiences.

The process starts when you're an infant.

In the first weeks or months of life, your neurons start connecting with as many other neurons as they can in a rather disorganized way in a process called exuberant synaptogenesis.

Baby's brains aren't just messy though, they're also hyper connected and many of these connections will disappear before adulthood.

We have more synapses as infants than we do during any other period of our lives, linking the regions of our brains in weird, unusual ways.

Because of our brain's early overactive cross wiring, some scientists hypothesize that we may all be born with synesthesia, which might explain why babies all look so surprised.

So, what happens between diapers and adulthood that leaves most of us synesthesia-free?

Well, as we grow older, some information highways get more traffic than others.

So, our brains start shutting down the underused roads in a process called synaptic pruning.

And by shutting down underused pathways, this synaptic pruning makes our brains more efficient.

But for someone with synesthesia, that pruning process missed some of the connections that linked different senses.

That means now when one sensory region of the brain lights up, the connected region can also be activated.

For example, when someone with auditory olfactory synesthesia hears music, which is processed by the temporal lobe, it can also simultaneously activate the area in their frontal lobe that's associated with smell.

So if you have auditory olfactory synesthesia, a lullaby might smell like lavender or heavy metal might have the same aroma as monster cheese.

Since it probably has its origins at birth, technically, anyone can have synesthesia, but about 40% of people with synesthesia do have an immediate family member with the same condition.

So if you don't have synesthesia, blame your parents, I guess.

But it might not be so simple.

How can we be sure that experiences of synesthesia aren't simply because we're associating different experiences from our memory and not because of overlapping brain wiring?

For instance, rather than experiencing an actual blend of senses, someone could simply remember the colors of the letters in their fridge magnet set.

Or maybe I think heavy metal smells like cheese, because I once went to a particularly stinky concert For a sensory experience to qualify as synesthesia, it has to have a few qualities.

First, both senses have to turn on simultaneously without any delay.

So, it's not that you hear music, and then remember an associated smell milliseconds later.

For synesthetes, the music and the smell are processed together as one input.

Additionally, the connection between sensory inputs has to be involuntary.

You're not trying to connect metal music with gross cheese smells.

It just happens, okay?

And finally, these associations have to be consistent over time.

So every time you hear metal music, whether that's next week or next decade, you'll still get hit with a bold whiff of melty cheesy goodness.

When many of us who don't experience synesthesia hear about these sensory experiences, it can be hard to believe they're real.

- Tell the people who you are.

- Hey, I'm P.W.

Shelton.

I'm an editor and animator here at "Be Smart."

- Give yourself some confetti or something.

Oops, that's good.

- Yeah, I'll do that later.

- So, I hear you got a bit of the synesthesia.

- Yeah, I got a case of that.

- There's like 150 something kinds.

What's yours?

- Years ago, found out that I had something called lexical-gustatory synesthesia, and it's something I've had ever since I was a kid.

And it's just a little quirk where I kind of can smell, taste words.

- That can be any word?

- It's a long list of words.

- Guitar.

- SpaghettiOs.

- Bird.

- Leftover cold rotisserie chicken, not hot.

- Legos.

- Eggo waffles.

So, it's Lego, egg, yeah.

- Okay.

I mean, you couldn't be making these up.

These are just two weird, but cool.

- Thank you.

Thank you.

- All right, what about "Be Smart."?

- Bee would be, there's a candy, it's called Bit-O-Honey and that's what the bee reminds me of.

And smart is Smarties.

And a lot of the things that you could ask me, they would be similar to whatever food you'd be talking about.

If you ask me, "Oh, what does a pineapple smell like?"

That would just smell like pineapple.

- If you're hungry, do you ever just sit down and read the dictionary?

(P.W.

Shelton laughing) - No.

Nothing like that, no.

I just eat when I'm hungry.

- Yeah.

I gotta ask, what's my smell?

- Yours is lunch room spaghetti from elementary school.

(Joe laughing) - Of all of the smells you could have come up with, that's the one I get?

- And it's always the same.

You ask me 10 years down the road and Joe will be lunchroom spaghetti.

- Synesthesia actually gives people an incredible new way to experience the world.

Just imagine if you could see music looping around you as your favorite Taylor Swift song plays, or if words jumped off the pages of your favorite books and swirled around in technicolor, or if you could literally taste the rainbow.

Eat your heart out, Skittles.

Science tells us that being a synesthesia comes with some other major benefits too.

For instance, one study found that people with ticker-tape synesthesia, where they literally see the words that they hear, are better able to retain and use information over short periods.

Additionally, researchers found that people who have blended sound color and space senses perform better on visual tasks and have better spatial awareness.

And that same study determined that these types of synesthetes are much more likely to be artists, which maybe isn't surprising since some of the world's most famous artists, like Vincent Van Gogh, allegedly had synesthesia too.

However, even though we may all be born with the potential for synesthesia, it seems like we can't learn it once we've lost it.

In 2018, researchers in the UK tried to teach young adults letter color synesthesia.

They trained people to associate letters with specific colors through a lot of repetitive tests, like flashing colors, and then asking people to remember which letters they went with.

While participants did develop associations between letters and colors, the results only lasted a few weeks.

Scientists aren't sure why, but it is clear that it's really hard and maybe impossible for adults to learn the synesthetic connections that just happen naturally for other people.

So unless we figure out a new way to rewire our brains, synesthesia is probably off the table for most of us.

But maybe we can get a glimpse of what it's like to be a synesthete.

For instance, humans tend to link certain colors with specific emotions almost universally.

When we see red, we think anger or love.

Black equals sadness.

And yellow, well, that more often than not signals joy.

Take a look at these two drawings, which one would you name bouba and which one would you name kiki?

If you said this is bouba and that's kiki, then you're in good company 'cause about 88% of people studied agree.

And it's not just English speakers either.

Researchers have found that people associate the round shape with bouba and the spiky boy with kiki across more than 25 languages.

What you just experienced isn't technically synesthesia.

It's sound symbolism, where we connect the sound we make to the meaning or in this case, the shape of something else.

Researchers aren't quite sure why this happens so strongly with these two sounds, but the leading theories that our mouths mirror the shape of the object as we speak.

So while that isn't technically synesthesia, it can maybe give us a taste of what it's like to experience blended senses.

But studying synesthesia can have long-term benefits for all of us.

Synesthesia can shed light on how our brains make, and then break connections throughout our lives.

And when we understand how that happens, we can better support people with conditions like autism, which can affect how senses are processed.

And of course, synesthesia is an important reminder that there is more than one way to sense the world.

Stay curious.