I shouldn’t have been all that surprised this week when the news came out that Physarum polycephalum, also known as slime mold, has now been shown to be capable of learning.

Physarum polycephalum
Image: Norbert Hülsmann/CC

At least, it has been proven that P. polycephalum is able to habituate – i.e. when an animal, after a period of exposure to a stimulus, stops responding to that stimulus. 

After all, P. polycephalum has shown itself able to solve mazes and create efficient nutrition networks that resemble urban transportation systems.

Slime mold placed in an environment in which food is placed in the same layout as the Tokyo metropolitan area builds a network similar to the actual Tokyo transport system.
Image: Science/AAAS

Over a nine day period, scientists at the Research Centre on Animal Cognition (CRCA) in Toulouse, France, showed that slime mold could learn to ignore bitter (but harmless) substances such as quinine and caffeine that were placed between the mold and a food source.

Initially, the slime mold was reluctant to pass through the bitter substances as if they were dangerous. After a few days, the mold learned to ignore the substances as if they weren’t there. Further, slime mold exposed to one bitter substance was able to transfer that learning to another bitter substance and treat it as a benign obstacle.

What this research shows is that the roots of learning go way back to single-celled organisms. Around 500 million years before humans enter the scene.

As Iain Couzin says in a short video that shows slime mold solving a maze, “Intelligence emerges from the interaction among much simpler components.”

P. polycephalum finding the shortest path to a food source.
Image: Via Forgetomori

So it’s no shock that this smart set of single-celled protists can learn.

What’s surprising is that P. polycephalum does all this without a nervous system or a brain. Surely this should win old P. polycephalum a bit of respect and teach us a bit of humility. Slime mold doesn’t have much, if anything, to learn from us. It appears we have quite a bit to learn from and about slime mold.

Not to over-anthropomorphize, but: On one level, this makes me wonder why we humans, collectively, can be such slow learners when it comes to our overall well-being. We have big brains! Among the biggest! And what we do most efficiently is get ourselves into trouble.

On another level, it gives me hope that if we can get past what we see as all our differences, we can aspire to be as efficient, cooperative and smart as the brainless but intelligent P. polycephalum, the lowly slime mold.

Physarum polycephalum in the wild.
Photo: Nature ID