The Japanese biologist Toshiyuki Nakagaki showed in 2000 that the slime mould Physarum polycephalum, a single brainless cell, could find the shortest route through a maze to food, and in 2010 that, growing between oat flakes laid out like the towns around Tokyo, it built a network much like the region’s railway. His team also found that it could anticipate a regular event. Scientists still argue over whether this deserves the word intelligence; for Therapeutic Shamanism, a being so unlike us is conscious in its own way, whatever the maze shows.
Who is Toshiyuki Nakagaki? #
A Japanese biologist, born in 1963 in Aichi Prefecture, who is a professor at the Research Institute for Electronic Science at Hokkaido University.1 He has worked on the same species of slime mould for some four decades. He first came across one as an undergraduate in Hokkaido, a lemon-yellow stain in a petri dish, and it set the course of his career. “I was just impressed with how fast it moved,” he has said.2 Since then he has studied how the mould senses, moves and makes its networks, and has worked on robots and on the gaits of centipedes.1 He has twice won the Ig Nobel Prize, given for research that is both amusing and thought-provoking: in 2008 for cognitive science, for the maze, and in 2010 for transportation planning, for the railway study.1
What is a slime mould? #
Not a mould at all, and not a fungus, plant or animal either; slime moulds form a group of their own. Physarum polycephalum is often found as a glistening yellow patch creeping over the leaf litter of a forest floor. Even when it spreads over a couple of square metres it is a single cell containing many nuclei, with no brain or nerves of any kind. It moves at up to a centimetre an hour, fast for its kind, reaching out towards bacteria and other food with fingers of living jelly, and its living jelly can be seen swelling and contracting as it flows through a network of tubes.3
What happened in the maze? #
Nakagaki and his colleagues let a Physarum spread through a small maze cut into agar, then placed food at two points. The mould first filled the passages. Then it drew back from the dead ends and the longer routes, until only a single thick tube remained, joining the two food sources along the shortest path.4 Nakagaki’s own words after that experiment were “I thought we’d have to rewrite the dictionary.”5
Not everyone reads it that way. The biologist Anne Pringle points out that the mould does not ‘solve’ the maze as a person would: “It grows across all of the empty spaces, and then withdraws from everything but the shortest route.” A maze of right-angled corridors is nothing a slime mould meets in a forest; it is a human puzzle, set because humans count solving it as intelligent.5
What was the Tokyo railway experiment? #
A test of how well the mould designs a network. In a study published in 2010, Nakagaki and colleagues laid out thirty-six oat flakes in the pattern of Tokyo and the towns around it, started the mould at ‘Tokyo’, and shone light on the areas standing for mountains, lakes and sea, which the mould avoids. It spread out, linked the flakes, and then thinned its network to the tubes that carried the most. The result came close to the real railway system around Tokyo, about as cheap to build and about as efficient at moving things, though somewhat less able to survive a broken link than the real network.6
The team then wrote simple rules in which each tube thickens when more fluid flows through it and thins when less does, and found that these alone produced efficient networks, offering ideas for engineers designing transport and communication systems.6
Can a slime mould remember and anticipate? #
Some experiments suggest it can. In 2008 Nakagaki’s group blew cooler, drier air over moulds crawling along a narrow track, three times, ten minutes at a time, at fixed intervals of between thirty and ninety minutes, most often an hour. Each pulse slowed them down. After three pulses the air was left alone, yet many of the moulds slowed down again at the time the next pulse would have come, roughly four or five in ten of them, as if they had learnt to expect it.7 How a single cell keeps time like this is still not understood.8
Other researchers have added to the picture. The Macquarie University researcher Chris Reid’s work suggests that the mould uses its own trail of slime as a kind of outside memory, avoiding places it has already foraged, and can tell its own slime from that of other species. And the slime-mould researcher Audrey Dussutour finds that pieces cut from one mould, clones of each other, will choose differently when given the same choice.8
Does this mean slime moulds are intelligent? #
Scientists disagree. For the researchers who study basal cognition, the idea that the tools of a mind are found throughout life, Physarum is a key example, a single cell that senses, remembers, decides and anticipates, and does so without a brain.9 The biologist Michael Levin refuses to put the word in scare quotes: “Sometimes the slime mould knows, not ‘knows'”, though that is “not the same thing as saying it knows that it knows.”10
Critics reply that the word is being stretched too far. The zoologist Alex Kacelnik warns that applying ‘cognition’ to brainless beings “hollows out the word itself”, and some biologists hold that experiments like the maze set the wrong problems or claim too much from the data.10 Pringle’s objection runs the other way: “why does Physarum have to be useful to humans to be interesting?”, since being a good engineer and being intelligent are human values.10 See What is basal cognition, and who argues that cells think?
How does this connect with Therapeutic Shamanism? #
In the question it raises. Most Westerners keep consciousness for humans and a few animals like us, and struggle to see it in beings very different from themselves: “A slug? A blade of grass? Bacteria?” In shamanism everything is made of Spirit, Spirit is conscious, and so everything is conscious, but in ways unlike ours.11 A brainless cell that remembers where it has been and expects the next cold gust is a vivid picture of a consciousness very unlike ours.
It also shows how much depends on speed. The mould’s movements can only be followed on speeded-up film. Consciousness operates at different speeds, and what may not seem conscious at our pace becomes apparent if we slow down enough.12
And Pringle’s question, why a being should have to be useful to humans to be interesting, points at the habit of ranking the world by its likeness to us and its use to us. Therapeutic Shamanism calls that habit the myth of human supremacy, and answers it with humility, since humans are the youngest and least wise of the PeoplesThe Peoples. The Animal People, Plant People, Standing People (the Trees) and Stone People: our elder kin, of whom the Human People are the youngest and least wise. A family, not a hierarchy. Read the full answer.13 See What is the myth of human supremacy?
Where does Therapeutic Shamanism see things differently? #
In what the maze is taken to prove. The experiments ask whether a slime mould can do something humans count as clever, and the argument then turns on whether that earns it the word intelligence. Tests built around our own kind of mind have the bias built in, and tend to prove to us that we are right.14 Therapeutic Shamanism does not need the mould to pass a human test to treat it as conscious. Consciousness and self-awareness are not the same thing, and there are kinds of consciousness, such as collective-awareness, that most people do not even recognise as consciousness.15 See Is the living world intelligent?
