The Intelligence of the Brainless | Natallia Valadzko

What is this branching yellowish ooze growing over a rotting stump in your local forest? Intertwined plant veins? A ball of mucus? A fungus? In fact, it might be the slime mould Physarum polycephalum, which was nicknamed Le Blob. It has no brain or a nervous system, but it can combine infinitely with other cells, consequently forming a superorganism. Surprisingly enough, it has recently challenged the anthropocentric claim on intelligence and creativity. Turns out Le Blob is able to break out of Petri dishes, solve mazes, choose the fastest route to the food source, and even anticipate future events. But… such behaviour requires intelligence! Doesn’t it? To answer if Le Blob is an astute being or not, we have to take a closer look at intelligence. And here is where things get complicated.

Intelligence is something humanity took pride in for centuries, meticulously documenting the progress of the human “genius”: language, the usage of basic and advanced tools later on, mathematics, poetry, developments in agriculture, manufacture, transport, and much more. And nowadays, considering the role Artificial Intelligence has occupied in many areas of modern life, we start asking even more questions: What if machines become self-aware? Can there be a new intelligent species? Is creativity not unique to humans? But the challenge is not even to find an answer to those questions but merely to define what intelligence really is.

Years on end, the term has been extended and appropriated in various ways. For example, in video or tabletop games, it refers to a quantifiable – yet unspecified – ability to be “smart”; in psychology there are ideas of emotional and social intelligence, which describe emotion management and understanding social cues respectively. But the definition of intelligence is still quite hazy. It is commonly agreed that intelligence is a problem-solving mechanism. This may include the ability to gather knowledge, to remember it, to learn, be creative, form strategies, etc. It can be perceived as a sort of toolbox that an intelligent being is capable of using in order to get the benefits, avoid unpleasant or dangerous things, and stay alive.

Even though etymology cannot define a phenomenon, it may point us in an interesting direction. Intelligence comes from Latin inter- (“between”) + legere (“choose, pick out, read”), which may imply that it is all about “choosing between”: collecting information about alternatives and making a decision. And yet, scientists tend to equate intelligence with a brain and restrict “cognition” to exclusively human abilities, dismissing intelligent behaviour of more primitive organisms as reflexive and mechanistic. We disregard complex behaviour of simpler organisms even though some of the hallmarks of intelligent behaviour are found in organisms that do not have brains at all.

Coming back to Le Blob, the creature has shown that it can retain and share information, learn, and choose the most efficient options. The most common experiments involved spreading out oats, the slime mould’s preferred food, and introducing obstacles like caffeine, salt, or sunlight. The superorganism of merged cells behaves like a colony that pulses and spreads wider when encountering something attractive, like food, or contracting when exposed to something repulsive, like light. As a result, it flows in the best possible direction. A mind-blowing illustration of this is a task given to the slime mould by a Japanese team of scientists: to find the most efficient transportation network in the greater Tokyo area. What they did was arrange oat flakes to represent key towns and cities and put Le Blob in the centre standing for Tokyo. The resulting slimy vein network looked eerily similar to the actual Tokyo rail system. No brain used.

It seems to exhibit the simplest form of learning – habituation. In humans, it is exemplified by us not minding the texture of the clothes after we put them on or ignoring non-threatening noise, thus, being able to focus on the more relevant aspects of our surroundings. Similarly, with more repetitions of the repulsive obstacles, P.polycephalum becomes habituated: it gets used to the harmless, albeit “unpleasant”, chemicals, starts ignoring them, and moves faster. But if you give it a longer time-out or introduce quinine instead of already “familiar” caffeine, it would again be reluctant to come in contact with it. This shows that the organism learns to differentiate stimuli and adjusts its response to them. No brain used.

What’s more, one slime mould can transfer this very primitive memory of its experience with different repulsive substances by merging with other slime moulds that never encountered them. As a result, if even one slime mould among the fused ones is habituated, all the merged moulds will behave as if they are already used to the chemicals and, hence, are quicker in their movement. No brain used.

Recent findings showcase other extraordinary “brainless” organisms that are capable of intelligent, and even creative, behaviours: sleeping jellyfish, Venus flytraps counting to five, and lichen “colonizing” bare rock, dead wood, and animal bones. If intelligence is indeed a toolbox of skills and abilities, then maybe one does not have to have a brain to exhibit intelligent behaviour. While human brains are extraordinary, perhaps we don’t have a monopoly on intelligence and can learn a thing or two about living communally and sustainably from the brainless.

Natallia Valadzko

Cover illustration: Katarzyna Kocur