Toshiyuki Nakagaki discovered a lemon-yellow slime mould in a Hokkaido petri dish 40 years ago, sparking a decades-long biological debate over cellular intelligence. According to researchers, the single-celled organism Physarum polycephalum can navigate mazes and optimize transport networks without a brain, challenging long-held assumptions about cognition across living systems.
How Slime Mould Mapped the Tokyo Railway Network
In a canonical 2010 study highlighted by the New York Times, Toshiyuki Nakagaki placed oat flakes on a surface to represent Tokyo and 35 surrounding towns. He released a Physarum specimen from the center, and the mould extended tubules to link the food sources together.
The organism created an efficient network that closely mirrored the actual greater Tokyo railway system. According to Nakagaki, the mould effectively bypassed human bias and politics to design an optimal transport layout. This performance earned Nakagaki a second Ig Nobel prize, this time in transportation planning, after an earlier win in cognitive science for his maze-solving experiment.
Challenging the Neuropurist View of Intelligence
Traditional biology held that cognition required neurons and a centralized nervous system, placing animals above plants and microbes. However, Adelaide University philosopher Pamela Lyon describes a shift toward a “biogenic” stance, arguing that traits like cognition are intrinsic to all life.
According to Tufts University professor Michael Levin, every individual cell possesses its own form of intelligence and cognitive ability. Opposing these views, traditional plant physiologist Lincoln Taiz and other “neuropurists” have criticized plant neurobiology and cell-cognition theories as examples of “brain envy” and unscientific anthropomorphism.
Pro Tip: When culturing Physarum polycephalum at home using commercial sclerotium packs, maintain consistent moisture and darkness to successfully revive the dormant slime mould from its dried state.
Cellular Memory and the RNA Debate
Researchers investigating brainless organisms continue to examine how slime moulds and other cells store memories. Macquarie University researcher Chris Reid found that Physarum uses its own sticky slime trails as an external aide-memoire to recognize previously foraged paths and avoid sterile areas.
Frequently Asked Questions
What is Physarum polycephalum?
Physarum polycephalum is a species of slime mould—technically a single-celled syncytium containing many nuclei—that creeps across forest leaf litter and consumes bacteria or microbes.
Can slime moulds actually solve mazes?
Yes. Laboratory experiments demonstrate that Physarum can locate the shortest route through a maze to reach food sources like oat flakes by growing through open spaces and withdrawing from inefficient paths.
Why is slime mould research controversial?
The research divides biologists because some scientists apply terms like “intelligence,” “learning,” and “memory” to organisms without brains, while critics argue this anthropomorphizes basic physical and chemical reactions.
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