Understanding how things like slime moulds and plants can learn without a brain or even any neurons could help us fight diseases and make smarter machines

Dr Audrey Dussutour

SNAILS, jellyfish and starfish have taught us that you don’t need a brain to learn. These seemingly simple creatures are capable learners, despite being completely brainless. Perhaps this is no great surprise. After all, it’s not as if they lack nerve cells. Strictly speaking, it’s neurons that enable learning – theirs are simply spread out, rather than being packed into centralised bundles.

But what if you take away the neurons?

Most life forms on Earth lack neurons, and yet they frequently manage to behave in complex ways. Previously, we have chalked this up to innate responses refined over generations, but it is beginning to look as if some of these humble non-neural organisms can actually learn. While that’s left some scientists scratching their heads, others are busy investigating how this ability could offer new approaches to fighting diseases and designing intelligent machines.

Take a slime mould. It certainly doesn’t look smart. This unusual creature, which is not a plant, animal or fungus, often resembles a glob of lemon curd that has fallen on the floor. Really, this manifestation is just one stage in the slime mould’s life, formed when many single cells, each with their own distinct DNA, mingle and fuse. The resulting yellow blob can grow to a few square metres, and is just one enormous cell containing thousands of nuclei.

In nature, a slime mould relies on chemical receptors on its surface to sense substances in its path as it creeps along the forest floor. If it gets a whiff of something attractive, like food, it will rapidly pulsate, pushing itself closer to the source. …