Thinking Without a Brain: Physarum Polycephalum, the Unicellular Wonder

Physarum polycephalum,  (c)  frankenstoen 2.5 Generic (CC BY 2.5)

When you think about intelligent beings, the first thing that pops into your head is likely humanity. Or perhaps another animal piques your interest: dogs, dolphins, or even a swarm of insects can all be thought of as clever entities. But a school bus-yellow, gelatinous blob? Probably not.

Physarum Polycephalum, more commonly known as slime mold, is challenging scientists’ perceptions of what it truly means to be smart. Functioning as an unicellular organism, slime mold lacks both a brain and a nervous system. Instead, it is comprised of millions of tiny nuclei enveloped by a single cytoplasm. It moves by contracting and expanding this cytoplasm in a pulsating motion, creeping at a pace indistinguishable to the naked eye. Contrary to popular belief, slime mold is no longer categorized as a fungi, but as a protist.

Is slime mold intelligent? Scientists seem to think so

A team of researchers at Hokkaido University in Sapporo, Japan, carried out an experiment that gave further insight into slime mold’s capabilities. The scientists, led by Toshiyuki Nakagaki, positioned food sources (oats) to mirror stations in Tokyo’s rail system. When first introduced to the plated agar, the slime mold spread out in a uniform sheet. However, this changed in a matter of hours, as the protist receded from areas without food. Ultimately, the remaining paths closely resembled the existing Tokyo rail system. Perplexing still is how slime mold was able to mimic a system that took countless human hours to design, all without a single neuron.

Another example of slime mold’s apparent reasoning is its aptitude for habituation, or when an organism learns to ignore stimuli deemed unimportant. This is something that humans do all the time. For example, although our noses constantly obstruct our field of view, our brains choose to filter it out. Audrey Dussutour’s study found that slime mold could learn to ignore bitter chemicals when they blocked a food source.

What does all of this mean?

With research findings suggesting slime mold can learn as a globule of basic macromolecules, our notion of intelligence is questioned. If this brainless amoeba can reach the same conclusions that humans painstakingly do, what truly separates us? On the other hand, harnessing slime mold’s algorithms would benefit us hugely. They may aid the development of self driving cars and other decentralized systems. Or perhaps this technology will help redefine the field of artificial intelligence. Whatever lies ahead for slime mold, only time will tell.

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