Slime Mould Studies Spur 40-Year Fight Over Intelligence in 1-Cell Organisms

1 articles · Updated · The Guardian · Sep 8

Forty years after Toshiyuki Nakagaki began studying Physarum polycephalum, his work still fuels a dispute over whether a brainless, single-celled slime mould can be said to learn, remember or make decisions.
2000 maze tests and a 2010 Tokyo rail-network experiment made Physarum famous by showing it could optimize routes to food, while later studies suggested it stores spatial memory in its own slime trails and can anticipate hourly stress.
That evidence has split researchers between biogenic thinkers, who argue cognition extends across life, and neuropurists, who say applying words like “intelligence” or “cognition” beyond brains misleads the public and weakens scientific meaning.
More than 10,000 Physarum papers in 25 years reflect wider pressure on biology from plant signaling, cell-memory research and AI-era debates over whether intelligence is a continuum rather than a neuron-bound trait.
The fight now centers less on any single slime-mould result than on definitions: what would count as proof of cognition, and whether biology has language precise enough to compare humans, cells and machines.