Hey smart people.

Joe here.

I need to warn you: This video is gonna be a little gross.

Especially if you're afraid of tiny… little... HOLES.

Or, maybe you're like me.

In which case you're probably wondering: Why exactly is this disgusting?

I mean, it's just a bunch of holes… right?

Trypophobia.

In Greek it translates to a fear… of holes.

But it can also include an aversion to bumps, clusters, blobs and bubbles.

It's actually pretty new as phobias go. The word was invented by an Irish blogger in 2005.

So there's not a lot of great data out there, but as many as 1 in 6 people may have trypophobia.

It's even more common than acrophobia, the fear of heights.

Yes, even ol' PewDiePie himself fears all things holey.

But… according to the people in charge of these things, trypophobia isn't even officially recognized as an actual phobia.

Wait, then what exactly is a phobia in the first place?

The definition of a phobia is an extreme or irrational fear of something.

Fear–in general–serves a good biological purpose - it helps us avoid deadly things, like venomous snakes or the edge of a cliff.

But when our brains take it too far, and we aim our fear at things that can't actually hurt us in that moment, that's a phobia.

Like a fear of spiders.

Sure, if you live in Australia then arachnophobia is not irrational, because Australia is full of scary things that can kill you.

But if you're just reading Harry Potter at bedtime and a little cellar spider joins the party, there's no reason to burn down your house.

You're not in any real danger.

Unless you knock yourself out running away from it or something.

It's irrational to be afraid of that little harmless spider friend.

A fear of a bunch of small holes?

It's definitely irrational.

But what if people with trypophobia aren't actually even… afraid of holes?

If it's not fear, it can't be a phobia.

Certain emotions do certain things to people's faces, almost universally.

Almost universally.

People experiencing fear typically have high eyebrows, their mouth is open, their eyes are wide.

But people feeling disgust typically have wrinkled brows, pursed lips, and crinkled up noses.

Now, there aren't a lot of scientists studying trypophobia.

Because, who would want to?

But we can study people's reactions, looking for these telltale signs.

Scientists have done this, and research is starting to suggest: trypophobia is more about disgust than fear.

Why did we develop a reaction like this, back in evolution?

Fear and disgust evolved for different reasons, but they both tell us to avoid a bad thing.

Fear helps us avoid immediate danger, usually by triggering the fight or flight response.

But disgust helps us avoid something different.

There have been plenty of theories on why disgust evolved, but they each only explain part of the picture.

Like helping us avoid rotten food or sick people.

It wasn't until a couple of decades ago that we came up with a unified theory of disgust.

A scientist named Val Curtis–that's Val Kilmer, guys–Ok.

So Val Curtis developed the idea that our innate disgust reaction evolved as a way to avoid crawly, wormy, oozy things that could cause infection and disease.

It's called the Parasite Avoidance Theory of disgust, and it's the top theory of why we find some things gross.

It falls into these six categories.

Basically, the things that disgust us risk having some microscopic danger hiding inside of them.

Like poop has bacteria.

Rotting food may have mold.

Flesh wounds could carry parasites.

Feeling disgust ensures that we literally physically close ourselves off and avoid those things.

We're even disgusted by things if they just don't seem quite right, our bodies way of saying, "You can't be too careful when it comes to parasites."

If we find it gross, we won't touch it or eat it, which makes it more likely that we'll survive and reproduce, and that's all natural selection cares about.

And because our brains have this awesome ability to generalize and categorize and remember, even things that look like dangerous things disgust us.

Clusters of holes?

They most likely remind people of something in one of those six categories of disgusting stuff.

I mean, think about it, a lotus seed pod does sort of look like the worst skin infection imaginable.

That may be why these images are particularly nausea-inducing.

Of course people and cultures and customs are very different, and what we find disgusting varies too.

The disgust response may be biologically programmed and universal, but maybe a lot of what we find disgusting is taught and learned.

More research is needed.

I'm sure there will be a lot of volunteers.

So if you have trypophobia, you may feel afraid of holes, but you're probably just disgusted.

And… that means it's likely not a phobia at all.

Unfortunately, we don't really know if trypophobia can be cured, but avoiding videos like this seems like the best way to deal with it for now.

So if your friend has trypophobia, don't show them this video!

And if you have it, I'm sorry you had to watch this!

But thanks for staying curious.