All language subtitles for NOVA.S47E10.Secret.Mind.of.Slime.1080p.AMZN.WEB-DL.DDP.2.0.H.264-GNOME_track3_[eng]

It creeps!

It crawls!

It's this big,
blobby yellow thing.

It's slime mold!

A slithering shape-shifter
like no other on this planet.

AUDREY DUSSUTOUR It reminded us

of this alien organism
from a '50s movie

that ate people.

"The Blob"!

This one-celled
wonder has no brain.

No brain, no organs, no neurons.

Yet it's able to do
some of the behaviors

we normally associate
with animals with brains.

How does it solve a maze?

It is amazing.

Escape captivity?

Compete for resources?

Build efficient networks?

You start to think,
does this organism

possess intelligence?

All of these are
fundamental components

to being smart.

No brain?

No problem.

Clearly now, we see

that this can be
done by one cell.

Can this ancient
organism shed new light

on the evolutionary
origins of intelligence?

We can think of them as
how intelligence started

way back.

"The Secret Mind of Slime,"

next, on "NOVA."

Lurking in the forest's
shadowy undergrowth

lies an unlikely predator.

It creeps along,
stalking its prey.

Yet it is not an animal.

It has a fondness for
dark, humid places,

yet it is not a fungus

nor a plant.

It's a single-celled organism,

but not a bacterium.

It's known as slime mold.

It has no eyes, no
mouth, no stomach,

no legs.

Yet it can "see," "smell,"

and move around

through its pulsating
network of veins,

gorging itself on bacteria,

fungi,

yeasts,

and growing exponentially.

This strange yet humble
creature holds secrets that have

biologists, neuroscientists,
and mathematicians

scratching their heads.

Because this organism, without
a brain or a nervous system,

seems capable of making choices,

solving complex problems,

and devising strategies.

And it is forcing scientists
to rethink intelligence

as something that does
not imply a need for a brain.

Tanya Latty is a researcher
at the University of Sydney

who studies slime mold.

You can find slime
mold all over the place.

They're in leaf litter,
they're in the soil,

they're on bits of wood.

They're small structures that
almost look like mushrooms.

Not only is Tanya an
expert on slime mold,

she's one of its biggest fans.

How could you not love them?

It's this big, blobby,
yellow thing, you know,

it's just fundamentally cool.

I stand by that!

"Slime Mold Identification
and Appreciation."

There it is.

She even follows
them on Facebook.

The spores are gorgeous.

They're, they're beautiful.

The slime molds might be
one of the most abundant things

in the soil.

There are spores everywhere.

Biologists have puzzled

over where exactly
this creature fits

into the great tree of life.

Slime molds branched
off from that tree

before the plants, the
fungi, and the animals.

They're single-celled organisms,
but the type of cell they have

is quite different
from bacteria.

There's at least 900
different species of slime mold

that we know about,

and that number is probably
a massive underestimate.

The slime mold most
people think about

is Physarum polycephalum.

It's bright yellow,
it grows really fast,

and it's become
kind of our lab rat

most scientists are studying,

probably because
it's the easiest one

to grow in the lab.

Some of them have great
names, like the Dog's Vomit.

They also come in reds and
grays and browns and white.

Tanya was a latecomer
to slime mold research.

She began her career
studying the behavior of insects.

I'm an entomologist by training.

I work with ants,

bees, and other invertebrates.

But ten years ago,

while researching bees
at Hokkaido University,

she had a chance
encounter with slime mold

through one of the most
respected experts in the field:

Professor Toshiyuki Nakagaki.

Slime mold is a serious
subject of study in Japan,

one going back generations.

The Emperor Hirohito himself

was a learned biologist

who established a
taxonomy of slime mold,

and even discovered a
new species of the organism.

In my research, I focus
on this single, simple cell

through the disciplines
of physics and math.

I was able to see how
he was doing things

and learn a little bit
about the slime mold.

Toshiyuki had been studying

how this curious
organism would react

when faced with a challenge
traditionally posed to animals.

He did some of the first
really awesome experiments

on slime molds solving mazes.

Could a slime mold find food

placed at the far
end of a labyrinth?

I had never even heard of
slime mold before I took this job.

So here you have this organism
that has no brain, no organs,

no neurons of any kind.

Yet it's able to do
some of the behaviors

we normally associate
with animals with brains.

It is mysterious.

Astounding.

Solving a maze is amazing.

How can a single-celled organism

have such a capacity?

Toshiyuki has devoted his
career to studying this question.

I mean, when you think about it,

99% of the living things
on our planet are brainless.

But they need to find food,

they need to find partners
to reproduce often.

They may need to
hide from predators.

How do you do all of that
when you don't have a brain?

When I came back
to Australia, I thought

it would be awesome to
have one of these as a lab pet.

And it lived in my
desk for a few weeks.

I started to notice
that it was doing things

a lot like my ants were doing.

So she introduced Physarum
to one of her colleagues,

Audrey Dussutour.

I was a post-doc in Australia

studying nutrition in ants.

It looked like an old omelet.

The next day, it had escaped
from the box we had put him in.

It reminded us

of this alien organism
from a '50s movie

that ate people...

And grew and grew as it ate.

It's unstoppable, it just
kind of keeps coming.

And then the world could fall
before the blood-curdling threat

of "The Blob"!

Physarum doesn't eat people.

It eats oatmeal, but
it's really a glutton.

It doubles in size every day.

I nicknamed it "Blob."

Physarum began consuming
their time and attention.

And soon, Tanya and Audrey

shifted the focus
of their research

to this remarkable creature,

so radically different than
any other they'd studied,

with abilities beyond
what could be expected

from a single cell,

beginning with an
unmistakable knack

for finding food.

Slime molds have receptors
all over the cell body.

And that allows them to detect

different chemicals
in the environment.

It's very similar to
our sense of smell.

We have receptors in our noses,

and we're actually
detecting chemicals

coming off of
our food in the air.

Slime molds are
doing the same thing,

but they're doing it through the
soil or through a liquid medium.

Like the surface
of a petri dish.

They're able to sense
the chemical cue

and that's what draws
them towards the food.

Slime mold's receptors
sense a wide range

of these cues in
their environment.

It can detect moisture
and perceive the pH.

It can perceive light
because it has photoreceptors.

So even though it is a
single cell, it is, all at once,

an eye, nose, ear, and so on.

But it was how Physarum
used these senses

that captured their attention:

an awareness of its environment;

an ability to navigate;

and how it moved
with seeming purpose.

Here's an organism
that knows how to react

and adapt to its environment,
consistently and efficiently.

They knew that
Physarum's receptors

allowed it to react
to different stimuli.

It will move towards a
substance, like sugar,

but it will also move away
from certain substances, like salt.

But was Physarum simply
reacting to these stimuli?

Or was it using these receptors
to do something more complex?

Was it taking in
this information

about its environment

and making choices?

So for their first experiment,

they would present Physarum

with one of the
most basic choices

facing any living organism...

what to eat.

We can offer it a choice
between different food sources.

The purpose of this experiment

was to see how Physarum
regulates its nutritional needs.

But before they
could even begin,

they'd have to determine

what exactly Physarum's
nutritional needs were.

In nature, Physarum
feeds on a diverse diet

of micro-organisms
from the forest floor.

But in laboratories
around the world,

they're fed a
single food... oats.

Slime molds inexplicably
love rolled oats.

And that's good for them,
but for this experiment,

we had to design
different diets.

So we had to invent
special recipes for Blob.

Making their
Australian laboratory

seem more like
a British bake-off.

We had to do a lot of
different mixing and cooking

to figure out

the ratio of proteins
to carbohydrates

that the slime mold
did the best on.

So, the ones that
maximize their growth.

We created these
sort of crèmes brûlées.

We called them custards.

35 different recipes.

Each had a particular
ratio of protein to sugar.

To determine which of
these recipes was best,

the judge in this test kitchen

was Physarum.

They placed Physarum on each
of these 35 mixtures of protein

and carbohydrates...
basically, sugar...

and found that Physarum
needed both to survive.

But too much protein, and
Physarum would split apart.

Too much sugar proved fatal.

With just the right balance,

Physarum grew and
remained healthiest.

Audrey and Tanya had
found Physarum's optimal diet.

Now they were ready to
test if Physarum could find it

when presented
with multiple options.

We offered Physarum a buffet.

In this buffet,

Physarum had a variety
of custards to choose from,

each with a different
ratio of protein to sugar.

Could Physarum find one
with the proper balance

among these seven
different ratios of nutrients?

There was one slight problem.

Physarum is slow,
it is extremely slow.

Way slower than a slug.

Not even half the speed of
the minute hand on this watch.

Physarum... is... slow.

At least 24 hours for
a single experiment.

So to observe and record
their slime mold experiments,

Tanya and Audrey relied
on time-lapse photography.

In images taken over periods
of hours and even days,

Physarum comes to life,

unfurling its
tendril-like extensions

called pseudopods.

It's detected that food cue, and
it's extended a pseudopod out.

I get the impression
they don't super-like

that blue food source.

In fact, it contains
levels of sugar

that would be
lethal to Physarum.

And so, it heads elsewhere.

You can see it's
sort of dividing

into a bunch of pseudopods...

It's contacted that
one in the middle.

I'm not sure if it's
actually chosen that one.

It's the best ratio
it's sensed so far.

It begins eating, and
continues searching.

Slime mold can, and so it does.

It'll first engulf the food

and then send out
pseudopods to start looking,

because you never know
what's around the corner.

The slime mold soon
abandons that source.

It's sort of shifted.

The slime mold clearly
likes the left side better.

On this side is the
best nutritional balance.

Given seven options,

Physarum found the optimal
ratio of protein to sugar.

Blob headed towards the custard
that would maximize growth.

It will always try to optimize

both protein and sugar.

But had Physarum
made a decision?

Was this truly a choice?

We have to be very careful

using words like
"choice" or "decide."

We're not saying
that they have feelings

or that they're thinking
or doing those decisions

the same way that we do.

What we are saying is that slime
molds are able to make choices

because, if you
give them an option

between two or more items,

they will consistently make
certain choices over others.

Choice or not, they
had conclusively shown

that Physarum had
effectively taken in information

about its environment

and turned that into action...

action that in
itself is mystifying.

It begs the question,
"How does a cell move

"if it has no appendages,

no legs?"

It's a system quite
unique in nature.

If you look at it
closely, you'll see

that it is crisscrossed
with a network of veins.

The veins of slime molds
are constantly pulsing,

and that drives it forwards.

In Bremen, Germany,

Hans-G ünther D
öbereiner and his team

study the mechanics of
Physarum's movement.

There is a stream of
what we call protoplasm.

You can see here that there's
a flow within these veins.

That flow is
produced by proteins

that wrap around the veins

and rhythmically
squeeze and relax,

propelling the
protoplasm within.

And that liquid is
driven through the veins

to the growth front of Physarum.

The growth front is Physarum's
forward-moving branches,

fed by these veins.

But how does Physarum
coordinate this movement

in order to navigate
towards its next meal?

In our bodies, we
have a brain that tells

the rest of our body what to do.

That's not the case
in the slime mold at all.

It's totally decentralized.

And so every bit of slime mold

is essentially
deciding for itself.

What "every bit" would be
in a single-celled organism

is confusing, even for the
people that study Physarum.

So to better understand
what the "parts" are

that make up this single cell,

Hans-G ünther's team
shredded Physarum

into thousands
of tiny fragments.

The veins, the pseudopods...

all of the familiar
structures... are gone.

What remains are
random bits of protoplasm,

the goo that
Physarum is made of.

For Physarum,

this is a minor setback.

Viewed under a microscope,

these bits are already pulsing.

And as they watch, Physarum
begins forming back together.

These separate,
small objects join up

to form an
interconnected network.

You can see more and
more of them coming together.

Physarum is reassembling itself

into its familiar
network of veins,

fanning out in every direction.

Hans-G ünther has found
that Physarum's parts

are interchangeable.

A dog is always a dog.

A bacterium is
always a bacterium.

But Physarum is more like...

A Transformer.

It's a natural,
biological Transformer.

Any part of the slime mold
can pretty much recreate

any other part
of the slime mold.

And that's because, if
you think of a slime mold

as being almost like a soup,

there is all these different
components of the cell

that do different jobs.

They can organize and
pack tightly to form a vein.

They can be less packed together

to form this
free-flowing cytoplasm.

It will just reorganize itself
and become a slime mold again

with all the normal
slime mold bits.

So it can totally
reorganize itself.

These individually pulsing bits

are the key to its movement.

If certain areas begin
beating faster than others,

Physarum will move
in that direction.

Cytoplasm will flow in the area
where there's the most pulsing.

And one thing that
controls these pulses

is Physarum's receptors.

Once that receptor detects
the food, that triggers

that part of the slime mold
that's closest to the food

to start pulsing faster.

And so the slime
mold starts to flow

in the direction of the food.

Hans-G ünther has been mapping

Physarum's patterns of
structure and movement,

and says that, in many ways,

it resembles the flow of traffic

on human
transportation networks.

In Japan, members of Toshiyuki's
team have been studying this.

Physarum is
particularly interesting

because it is, basically, an
adaptive transportation network.

In this experiment,

Physarum is meticulously placed

over the entire
surface of the labyrinth.

At the entrance and
exit are oat flakes,

to see how Physarum
will handle the presence

of two food sources.

One by one, it eliminates
unproductive pathways

until there's
just one vein left,

linking the two food
sources by the shortest path.

By reconfiguring
itself in this way,

Physarum has optimized
its intake of nutrients.

But two points are easy.

Toshiyuki began to
test Physarum's ability

to optimize its form
over many more points,

eventually increasing
the number to 37.

The number of possible
ways to connect 37 points

is somewhere in the
neighborhood of an eight

followed by 54 zeros.

Can Physarum find
the optimal way?

And to make it interesting,

Toshiyuki and his team gave
Physarum a real-world problem,

one that human engineers
had already solved:

find the most efficient
transportation network

in the greater Tokyo area.

Using oat flakes to represent
principal towns and cities,

Physarum is placed
where Tokyo would be.

Can Physarum create
an efficient network?

Physarum explores
its environment

and, as it discovers
the oat flakes,

reconfigures its
network of veins,

reinforcing the links
between the food sources

and making the others disappear.

What we're getting is
something that looks an awful lot

like the actual
Tokyo metro system,

far more like it than we
would expect by chance.

Physarum has created
an optimal network.

Something it's done
successfully for millions of years,

long before humans came along.

We noticed almost always,

when they were
searching a plate,

they would never go back over
where they had been before,

and that was unusual.

Unusual because that would
seem to imply that Physarum

would have to remember.

We assumed that it didn't
have any classic memory,

that it wasn't remembering
where it had been,

which left the question,
"Well, then, how is it doing it?"

The answer came
from Physarum itself.

It had been leaving a trail
of clues written in slime.

This gray stuff,
that's the slime trail,

which is kind of like the slime
trails that we see behind slugs.

So you have to ask,
"Does Blob use its trail

to memorize its environment?"

Ants emit trails of pheromones

to mark their paths to
where they've found food.

Then other members of
the colony use that trail

as an "external memory"

to navigate to
the food and back.

Because we worked with
ants, we were kind of familiar

with this idea of having
an external form of memory;

it's not encoded in a brain,
it's marked on the environment.

In Physarum's case, its
trail is a signal to keep away.

That slime is, in
fact, a repellent.

Slime mold never wants to
go back to where it has left

its own slime.

So we set up an experiment to
see if this slime was being used

as a kind of external memory:

the U-Shaped Trap.

The U-Shaped Trap was
an experimental challenge

used in early
machine-learning research

to test things like a robot's
navigational memory.

A robot is given a
goal, which it can sense,

and a U-shaped
barrier, which it can't.

I mean, if you don't
have a system of memory

or some other mechanism,

you just keep
running into the wall.

And that's not a good thing.

Robots without a system
of memory would often

remain trapped in this loop.

In this experiment,

Physarum's goal was food.

Blob can spot the food
source at a distance

because it is diffusing
into the environment.

If the slime mold

just follows that smell
cue, it's gonna hit a wall.

And without some sort of
memory or some other system,

we expect it

to just keep smashing
itself against that wall,

and it won't escape.

So what will Blob do?

So the slime mold would
go down, hit the wall,

but when it goes to
do it the second time,

it detects that it's
already been there

and sort of takes a step back,

and you can almost
see it tracing the wall,

and then coming up the
side and zipping down

and finding the food
source really quickly.

So once we'd shown that
Blob was able to do that,

we performed the
experiment a second time,

but this time,

we covered the
environment with slime.

We made Blob think it had
already explored the area.

The slime mold can still
detect there was a food cue

and it still moved towards it,

but it was unable
to tell the difference

between where it had been
and where it hadn't been yet.

And so because of that when
it got to the bottom of the U,

it just gets stuck and can't
quite figure out how to get out.

It was no longer able
to find the food source.

And so Tanya and
Audrey concluded

that Physarum's
trail does, in fact,

serve as an external memory.

For slime mold researchers,

the mounting evidence
of these behaviors

led them to pose a question

that makes many
scientists nervous.

When you see what Physarum
polycephalum can do...

it can get through a labyrinth,
create optimized networks,

escape from a trap,
balance its own diet...

you start to think: "Does this
organism possess intelligence?"

So that word is tricky.

Defining intelligence
is not an easy thing,

and certainly many people
have different definitions for it.

The question of intelligence

depends a lot on how
we define intelligence.

Due to the fact that
it is so tightly linked

to the human beings,

it is very difficult now

to speak about intelligence
in other organisms.

A commonly accepted idea is
that the only living organisms

who display intelligence

are those with a
nervous system and brain.

I say with certainty that I
believe this idea is wrong.

In my opinion, I call
this intelligent behavior.

For centuries, most
scientists believed

the trait of intelligence...

the ability to
reason and think...

was unique to Homo sapiens.

It wasn't until the mid-20th
century that researchers started

to document cognitive
abilities in our primate cousins,

as well as other animals,
farther and farther from us

on the evolutionary tree.

Chimpanzees and even
crows making and using tools.

Whales and dolphins using sound
to communicate complex ideas.

Birds demonstrating memories
of places, things, and past events.

Sea lions that can grasp logic.

And evidence that many
animals can actually count.

Audrey and Tanya
now found themselves

among the small but
growing ranks of researchers

pushing the boundaries
of intelligence

beyond the animal
kingdom altogether,

searching for signs of
intelligence in organisms

with no brains at all.

The first conclusive evidence
was soon found in plants.

In Florence, Italy, the
idea of plant intelligence

has become the focus of
some serious scientific study

thanks to these two biologists,

Stefano Mancuso

and Frantisek Baluska,

who founded the Society for
Plant Signaling and Behavior.

The notion of intelligence
in plants is not new.

Charles Darwin himself
faced ridicule by his peers

when, after extensive
experimentation,

he proposed that plants
possessed a cognitive organ

and that it resided
in their root tips.

Darwin says that
in the tip of the root,

there's the precise
equivalent of a small brain,

like the brain of an insect,
that guides the plant.

We started to
argue that this theory

is really not crazy theory.

They came to this
conclusion after conducting

their own root-tip experiments.

It was thought
that a root arrived

at an obstacle

and did something like
that to find a way out.

Instead, what I
saw was different.

The roots turned well
before reaching the obstacle.

They were able to sense
what was around them

and calculate the
shortest path in response.

Stefano thought that this
kind of "sensing" behavior

would require coordination
of the cells in the root tip.

He discovered that
a specific region

was sending out
electrical signals

to the surrounding area.

Could this be the "brain"
that Darwin hypothesized?

When this section was cut off,

the root could still grow,

but it lost the ability to
sense its environment

and adapt accordingly.

From this, Stefano concluded
that Darwin was correct:

plant roots did appear

to contain a kind
of sensory organ.

Plants are like
upside-down humans:

they have their
heads underground,

and the part we can see
is the reproductive part.

And that's how we
should look at plants,

something like this pot.

Since plants now did
seem to have some form

of sensory ability,

Stefano and Frantisek
began searching

for more complex behavior

which might conclusively
demonstrate intelligence:

memory and learning.

One of the most basic types
of learning in brained creatures

can be seen in these pigeons,

who've learned
not to fear humans.

They even tune them out.

Habituation, as it's called,

enables organisms to focus
on the important information,

while filtering out the noise
in the world around them.

To test for this type
of learning in plants,

Stefano and his colleagues

turned to this intriguing
specimen, Mimosa pudica,

which reacts to disturbances
by folding its leaves.

If this reaction is
purely mechanical,

they should respond this way
every time they're disturbed,

even after numerous disturbances
that don't prove to be harmful.

So they repeatedly
dropped plants

from a height of six inches...

not particularly
harmful for pudica.

And after only
five or six drops,

the plants stopped reacting.

And yet, when they were
disturbed in other ways,

they still responded
by folding their leaves.

We showed that Mimosa
pudica was able to memorize

different stimuli

and to differentiate

between a dangerous stimulus
and one that wasn't dangerous,

and then respond accordingly.

This was, indeed,
quite a sensation.

Stefano and his colleagues had
documented intriguing evidence

of memory and learning

in a brainless organism.

For Audrey, this raised
a tantalizing question.

So with Physarum we asked,

"Are we going to
find this kind of ability

that can be found in plants?"

She and Tanya had
proven that Physarum used

a kind of external memory.

But was it possible
that Physarum

possessed some
true internal memory?

Is slime mold capable
of remembering?

Is it capable of learning?

That question is the Holy Grail.

Proving that Physarum had
these capabilities could show

that a single-celled creature
was capable of intelligence,

and might very well force
scientists to reconsider

the idea of intelligence itself.

So we set up an experiment
to see if Blob learned things...

a habituation experiment.

The objective was to try
and habituate Physarum

to a substance it
was repulsed by.

In this case, salt.

Between this Physarum
and a tasty snack

is a bridge a few
centimeters long.

Normally, Physarum makes
the crossing in about an hour.

For her experiment,

Audrey coated
the bridge in salt.

Not enough to harm Physarum,
but enough to leave a bad taste.

It took Blob ten hours
to cross the bridge.

The next day, we'd do it again.

By day two, that same Physarum

was moving faster
over the salt bridge.

This time, it takes eight
hours to cross the bridge.

Audrey repeated this for
five days, and each day,

Physarum moved more
quickly across the salt bridge.

By the fifth day, Blob
takes no more time

than our "control" Blob that
crossed the bridge with no salt.

So Physarum ends up getting
used to a substance it doesn't like.

It seemed that Physarum
learned to tolerate,

or habituate to the salt.

Had Physarum actually learned
that the salt wasn't harmful?

If this were true, it would mean
that somewhere, inside Physarum,

there was a form of memory.

Of course, some were skeptical,

because we were
up against the dogma

that learning was
strictly reserved

for organisms with a brain.

So Audrey wasn't
leaving things to chance.

If you want to prove

that a single-celled
creature can learn,

you've got to be sure

you can convince
your colleagues.

On each of these
tiny salt bridges,

they repeated the
experiment, again and again.

DUSSUTOUR 4,000 times

on 4,000 different Blobs.

The results were consistent.

Physarum had
altered its behavior

through its past experiences,

a fundamental
definition of learning.

Audrey had demonstrated
learning and memory

in a single-celled organism.

A creature this simple

demonstrated
the ability to learn.

But how do they do it?

Audrey showed
very nicely in her work

that Physarum clearly has memory
and learned from its experience

to adaptively make decisions
about where it's going to go

and how it's going to
explore its environment.

All of these are fundamental
components to being smart.

Director of the Allen
Discovery Center Michael Levin

listens in on the
electrical signals

exchanged between cells.

My lab focuses
on bioelectricity.

All cells are
electrically active,

and these electrical
signals enable cells

to join into networks
that store memories

and process information
and make decisions.

It was previously thought
that these cognitive abilities

came from the conversations
between many cells.

But Physarum had
just proven that wrong.

Physarum is one single cell.

And so this takes us
away from questions

of cell-to-cell communication,

all these things that
multicellular organisms do

that we think of as really
important for cognition,

but clearly now, we see

that this can be
done by one cell.

Michael learned a lot
about cellular communication

from his work with a
curious multi-celled creature

called a planarian.

A small aquatic worm
with the unusual ability

to regrow missing or
damaged parts of its body.

They regenerate
every part of the body.

So if cut into pieces,
every piece of a planarian

knows exactly what a standard
planarian body should look like.

When a planarian is cut in half,

its cells regenerate to
rebuild a head at one end,

and a tail at the other.

Everything that's missing
in the correct location,

and it stops when it's done.

But how?

Michael and his team began
to tinker with planarian cells

to see if they could
affect how these worms

controlled their regeneration.

We've discovered

that part of this control
is an electric circuit

that allows these cells to
store this kind of information.

And what we found is
that if we temporarily...

just for 48 hours...

alter this electric
circuit, and, in essence,

rewrite the finely
encoded pattern memory

of these tissues...

When they regenerate,
they can regenerate

as two-headed animals.

Michael and his team
did this without any kind

of gene editing.

It was done purely through
the manipulation of the signals

between its cells.

And so this tells you

that the information
that is needed

to specify what kind of
body you are going to make

is not entirely
specified in the genome.

Michael says that cells function
like electronic processors.

Bioelectricity is the software
that is run on these cells,

and it can be rewritten.

Michael wondered if Physarum
was using bioelectricity

as its system of memory.

What does it mean for
a chunk of cytoplasm

that you can pick up and
hold in your hand and analyze

molecularly,
electrically, and so on

to really store an
experience or a memory

or an inference from
past experiences?

So they tested Physarum's veins

for signs of
bioelectrical signals,

and found that it
produced electrical waves

that matched the flow
of its protoplasm within.

What we're doing is
attempting to read the mind

of the Physarum.

As it turns out, reading
Physarum's mind

is all about body language.

One of the important
things about Physarum,

its body structure and its
behavior are simultaneous.

In other words, the behavior
of the slime mold is executed

by altering its body structure.

Meaning, if Physarum was
communicating internally

using bioelectric signals,

those signals would change
along with Physarum's shape.

Michael's colleague
Andrew Adamatzky

attempted to communicate
with Physarum

by sending it
electrical signals.

He found that different
signals would cause Physarum

to grow in different ways.

Some signals sent
between two points

made Physarum
reconfigure its body

as it would between
two oat flakes.

Other signals repelled Physarum,

causing it to shift its body
away from the source,

much in the way
it does with salt.

Andrew and Michael believe
that this shows Physarum

is using bioelectricity
to process information

as it adapts to
the world around it,

and that Physarum's simple
design was a step along the way

towards the evolution
of multicellular organisms

with specialized
cells like neurons

and more complex
brain circuitry.

I think evolution
discovered very early on

that electricity and the
circuits that you can make

out of very simple
electrical components

are an extremely
powerful and robust system

for processing information,

making decisions,
storing memories.

Things it now appears
that Physarum was doing

long before the arrival
of creatures with brains.

We started to wonder

whether a Blob that
had learned something

could transfer its
learning to another Blob.

In other words: could Physarum
communicate a memory?

Because of what she had learned

about Physarum's
shape-shifting nature,

Audrey knew she
could cut it into pieces

and it would re-form.

If you take a Blob
and cut it in half,

you always end up
with two separate Blobs.

So how does that work?

It works because of
Physarum's odd, soupy anatomy.

Most single-celled organisms
have a single nucleus.

When they grow by dividing,

each new cell still
has a single nucleus.

If you were to cut that in half

you'd have two
halves of a dead cell.

But when Physarum
grows, its nuclei divide,

and yet they all remain
within the same cell membrane.

And that's why, when you
divide one Physarum in half,

you will have two
complete living Physarum.

And these Physarum

can also join together
with any other Physarum

that they encounter.

If you then take those two
Blobs and put them side by side,

they'll combine.

For Blobs, one
plus one equals one.

The fusion occurs when the
two membranes stick together.

They open up, and then
the networks of veins

connect to create a
single, autonomous Blob.

So Audrey brought together
thousands of Physarum

that she had accustomed to salt

with others that weren't...
so-called naïve ones.

If we allowed two Blobs to
fuse together for three hours,

the information passed
from one to the other.

The naïve Blob now liked salt.

It looked as though
the memory was passed

through the system of veins.

Slime mold demonstrated
the ability to communicate

the information it had learned.

And over time,
Audrey began to notice

that Physarum
from different places

showed different behaviors.

To Audrey, this is
slime mold personality.

We realized that there
were lots of differences

between our Blobs.

Depending on where
they came from,

her Physarum seemed to
have distinct characteristics.

The Japanese Physarum is fast.

The Australian careful
and well-mannered.

Its behavior is much
more consistent

from one day to another

and it does not escape.

The American is... problematic.

When the American Blob arrived,

we gave it organic oat flakes.

And it completely refused.

It even got out of its box

because it preferred the
well-known American brand.

She put them to the test
in a 250-millimeter dash.

And out of the blocks, Japan
is certainly showing speed,

with America close behind.

The Japanese Blob

is extremely fast, but
often makes bad decisions.

Australia has not yet started.

The Australian Blob

takes a little more
time to make decisions.

Japan, now sending
pseudopods in the wrong direction,

has lost its lead to the U.S.

But the U.S. appears
to be slowing down,

possibly attempting an escape.

And Japan takes back the lead.

Australia still not
sure whether to start.

America, now
moving forward again...

And the winner...

Japan!

The discoveries
of these pioneers

studying cognition in
brainless organisms

have scientists
rethinking thinking.

Organisms like slime
mold provide a window

into evolution's
early experiments

in problem solving.

We're just starting to scratch
the surface of understanding

the cognitive
capabilities of these really

radically different
biological architectures.

We can think of them as how
intelligence started way back.

The early origins
of decision making.

We can also learn a little
bit about some of the rules

that underlie problem solving

across lots of different
types of systems.

And more importantly,
for us, at least,

early solutions to
problem solving like these

would lead to the
specialization of cells.

They're an example
of the most basic form

of multicellularity.

They don't have organs
or anything like that,

but they're the very beginning
of what we would expect to see

in multicellular life.

Neurons did not appear
from scratch during evolution,

but actually are the result

of the specialization of
much more ancient cells.

All of the machinery that we
find in neurons, in synapses,

all of these things were present

even in our
unicellular ancestor.

Leading to the development
of more complex life,

and eventually, to
creatures like us.