What Can Slime Molds Teach Psychologists About Learning?

A slime mold is a single-cell protist that navigates damp forest-floor environments to find food. It reorganizes its body when it encounters food, retracting from areas with less food. Experiments test whether it can learn by repeatedly exposing it to a narrow bridge that is harmless but unpleasant. Initially, the slime mold avoids the bridge and reaches the food slowly. With repeated trials, it crosses the bridge faster each time, indicating experience-dependent behavioral change. Defining learning behaviorally rather than neurally enables study of learning across systems that lack brains. A functional view supports comparison of learning across diverse biological systems within a shared scientific framework.

"The yellow blob that you see in the picture at left is a slime mold, a strange one-cell organism that lives in damp, shadowy areas on the forest floor where it slowly navigates its environment, searching for decaying matter, fungi, and bacteria to feed on. When it finds a food source, it reorganizes itself, retracting from areas with less food."

"What is really interesting from a psychologist's perspective is that this single cell shows complex behaviors such as optimizing paths, solving mazes, and adapting to its environment in efficient and sometimes unexpected ways. Scientists also examined whether slime mold can learn. At first, this seems very unlikely. Learning, we tend to think, happens in the brain. No brain, no learning."

"Imagine the following experiment (shown in the picture below): A slime mold sits in a petri dish. Nearby, another dish contains food, connected by a narrow bridge. There's just one problem: the bridge is covered in substance that is harmless but unpleasant for the slime mold. The slime mold therefore remains mostly on its side, with little expansion onto the bridge. But eventually, it extends across and reaches the food."

"Now the situation is repeated multiple times. Something changes. Over time, the slime mold reaches the bridge and crosses it faster each time. It seems that what was i"

Read at Psychology Today