(classical string music)
- Pop quiz, hot shot.
Have you ever tickled an ape before?
It could work, as tickling is common
between many types of primates.
What about a rat, you
ever tickled one of those?
You'd know if you had because rats let out
this high pitched chirp
when you tickle them,
it's kind of like rodent laughter.
Okay, maybe some of you
beast masters out there
have tickled both a rat and an ape.
But can you tickle yourself?
Probably not, because
that's kind of impossible.
Under your skin, there are
millions of nerve endings
that alert your brain
whenever you touch something.
A light touch, what we usually
associate with tickling,
is analyzed by two regions of the brain.
The somatosensory cortex,
which processes touch,
and the anterior cingulated cortex,
which processes happiness.
Together, they process the
two types of tickle sensations
that we can experience.
The first is knismesis.
This is the light sensation you feel
when something like a feather
brushes against your skin,
maybe giving you goosebumps.
The second, gargalesis, is more like
when your older brother holds you down
and tickles you until you
laugh so hard that you pee.
This is the kind of tickling
that you cannot replicate yourself.
Evolutionary biologists
believe that we laugh
when we're tickled as an
innate submissive response
to a potential attacker.
These same biologists theorize
that we, you know, humans,
developed tickling so we
could teach our children
how to defend themselves from attacks.
Think about it, the areas
where we're the most ticklish,
the underarms, the stomach, and the neck,
are also the most vulnerable.
This next part is some
Black Widow, Red Room,
lethal training, so pay attention.
Your underarm is home
to veins and arteries.
And because your rib
cage doesn't protect it,
someone could easily access
your heart through there,
especially with a long enough blade.
Likewise, your stomach doesn't
have any defensive bones
and your neck has two important arteries
as well as your trachea,
bringing air to and from your lungs.
We're aware of these
points of vulnerability,
but we still can't
tickle ourselves at them
because our brains know that our own hands
don't pose a legitimate threat.
MRI studies have shown
that your cerebellum
actually alerts the rest of your brain
when you're about to tickle yourself.
This filters is out as
unnecessary information
and mutes the sensation.
So, theoretically, any situation
that confuses your brain's ability
to predict its own actions
should allow you to
tickle yourself, right?
Well, sometimes.
Schizophrenics, for example,
can tickle themselves.
Researchers theorize
that schizophrenic brains
have biochemical or structural variations
that keep the cerebellum
from alerting its owner
when they're about to tickle themselves.
This means they can't tell the difference
between their hands or your hands
or the tentacles of a giant squid.
So what about you?
Even though science says it's impossible,
I suspect someone out
there has a weird story
about tickling themselves.
If you like how we talk
about them there sciences,
make sure you subscribe so
you don't miss another episode
of the weird, creepy world of Brain Stuff.
