How Can Slime Mold Think Without a Brain?

Slime molds are collectives of single-celled organisms that don't have neurons, much less brains, but they can move, solve mazes, and remember where food is located. Learn what we know (and don't know!) about them in this episode of BrainStuff, based on this article: https://science.howstuffworks.com/life/biology-fields/slime-mold-facts.htm

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff, Lauren
Bolebon here. For a long time, nobody understood slime molds.
To be clear, no one really understands them now either,
But scientists now know that these pulsating piles of jelly

(00:22):
found on rotten logs in the forest are not fungi,
but are in fact more closely related to amieba's And
though there's nary and neuron in a slime mold's entire
gelatinous body, they seem to be able to solve relatively
complex problems. There are over nine hundred species of slime

(00:42):
molds living in the soils, leaf litter, and rotten logs
of this planet and other appropriately damp and humid areas
like maybe your bathroom. A Researchers have found a slime
mold cast an amber dating back at least one hundred
million years that remains entirely unchained from one you could
find today. A slime molds in general, though, have probably

(01:05):
been squishing their way around Earth for around a billion years.
It's possible that they're one of the first multicellular ish
organisms created by single cells joining and working together. Slime
molds are a really diverse group. They can appear in
any color except true green, a being that they lack chlorophyll.

(01:27):
Some called cellular slime molds live mostly as a single cell,
but may collect with others in a swarm in response
to chemical signals like food shortage or gotapprocreate now. Others,
called plasmordial slime molds, spend their entire lives as one
humongous organism enclosed in a single membrane. These are what

(01:50):
happen when thousands of single cells meet up and fuse together.
Either way, Once the cells of a slime mold are
in a collective, they can network and share resources. Slime
molds can form up in the shape of delicate lattices
or bulbous masses. They can remain microscopic or form collectives

(02:12):
ten feet long or longer now that's about three meters.
Given the motivation of, for example, finding food, those collectives
are capable of crawling like worms, towards a source of
nutrients or light, where nutrients are more likely to be.
The thing all slime molds have in common is their
life cycle, loosely resembling that of a fungus, which is

(02:35):
why taxonomists lump them in the fungi kingdom for so long. Basically,
when they vacuumed as much food out of their environs
as they can, they turn their bodies into clusters of
spore packets, usually on stalks and sometimes wildly colored, called sporangia.
These fruiting bodies disperse a fine mist of spores into

(02:56):
the air, which germinate wherever they fall. The single celled
organisms that spring from these spores start the slime mold
life cycle over again. For the article, this episode is
based on How Stuff Works. Spoke by email with Tanya Laddie,
who studies slime molds in the School of Life and
Environmental Sciences at the University of Sydney. She said, we

(03:20):
still know very little about the ecology of wild slime molds.
For example, how they interact with other organisms and what
role they play in ecosystems is still somewhat mysterious. A
Lattie studies cognition in both slide molds and insects, and
though we don't give insects much credit for their intelligence,

(03:40):
with slime molds, the already tricky concept of cognition gets
even weirder. Alattie said, slime molds and social insects are
both decentralized systems, where there is no leader in charge
of decision making. However, in the case of insects, each
individual operates both at the india visual level they have brains,

(04:02):
and at a collective level in slime molds, it's much
harder to even define what an individual is. We humans
rely on our brains for cognition, but even without a
giant brain such as ours, other animals do have the
ability to reason, learn, plan, and solve complex problems. A take,

(04:25):
for instance, the octopus, a cephalopod closely related to clams
and snails. It has a brain, but most of its
neurons are spread throughout its squishy body, mostly in its arms. Still,
an octopus has an undeniable intelligence. It can learn how
to open new kinds of containers to get snacks. It

(04:46):
can tell the difference between humans who are dressed identically,
or even make an escape from a tank, out a
drain pipe and back into the ocean. But this impressive
cognitive functioning bears no physiological relation ship to hours. The
neural processing equipment of an octopus evolved basically completely separately
from ours because our evolutionary lineages separated over four hundred

(05:10):
and sixty million years ago, but slime molds don't have
brains or even anything that resembles a neuron. There's a
lab friendly slime mold species named Physarum polycephalum, which means
many headed slime mold, though it's been affectionately nicknamed the
blob by researchers. It's bright yellow in color and can

(05:33):
move in gloopy filaments that look a bit like fans
of coral Researchers found that it can solve mazes. When
scientists place food at the end of a maze, the
mold will extend tendrills down different corridors and back out
of dead ends until it finds the food, all within
just a few hours. So while the process of learning

(05:57):
is completely different in a slime mold versus an octopus
versus a human, in each case, the outcome can look
basically the same. One type of learning slime molder capable
of is habituation. You do this too. You can get
used to the temperature of a cold lake after a
few minutes, or to the initially unpleasant buzzing sound of

(06:18):
a fluorescent light in a room. Your brain helps you
ignore the annoying sensation of the cold or the noise,
and similar to humans, the aforementioned blob can habituate to
environments and chemicals that it doesn't love acidic, dusty, dry,
salty places, or chemicals like caffeine or quinine if it

(06:40):
means it's going to get rewarded for putting up with it.
And not only can slime mold habituate to less than
ideal circumstances if it means they'll be rewarded, they also
seem to be capable of memory. The blob, for example,
seems to be able to remember things. An experiment involving
slime molds the intentionally habituated to salt, a known repellent,

(07:03):
before going into a dormant period, showed that they remembered
how to become habituated to living in a very salty
environment after a year of lying dormant. They also seem
to be able to decide which direction to travel based
on food that they've encountered there before, and researchers are
still exploring slime mold's capacity for and mechanisms of processing information.

(07:28):
The hope is that by figuring out how a decentralized
intelligence like a slime mold functions, maybe we can learn
something from them. Today's episode is based on the article
Brainless Footless slime molds are Weirdly Intelligent and Mobile on
how stuffworks dot Com, written by Jesslin Shields. Brain Stuff

(07:51):
is production of iHeartRadio in partnership with how stuffworks dot
Com and as produced by Tyler Klang. Four more podcasts
my heart Radio, visit the iHeartRadio app podcasts, or wherever
you listen to your favorite shows.