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Brainless slime capable of learning

Researchers said their work is vital to "understanding of when and where in the tree of life the earliest manifestations of learning evolved."

By
Brooks Hays
A slime mold was able to learn that a bitter substance blocking its access to food was harmless. Photo by Audrey Dussutour/CNRS
A slime mold was able to learn that a bitter substance blocking its access to food was harmless. Photo by Audrey Dussutour/CNRS

TOULOUSE, France, April 27 (UPI) -- Most people would say being intelligent requires a brain. New research suggests it's not necessary for learning. A study out of France showcases the learning capabilities of a brainless single-celled organism.

All living organisms have to adapt, even those without a brain or central nervous system. A plethora of research has highlighted the ability of bacteria, viruses and other single-celled organisms to adapt behavior -- to build up resistance to antibiotics or adopt new hosts.

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These changes happen over generations, however. They are evidence of evolution, not learning as most scientists have defined it.

A protist, or slime mold, named Physarum polycephalum is changing the way scientists think about the evolution of learning and intelligence.

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To test the protist's ability to adapt across a shorter time frame, scientists at the French National Centre for Scientific Research and the University of Toulouse subjected to the slime mold to a simple obstacle course -- a food source located across a bridge.

For some slime groups, the bridge, a petri dish, was impregnated with a bitter but harmless substance. Some faced a puddle of coffee, others were blocked by a pool of quinine. A control group had only to cross an unpolluted bridge.

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At first, the slime molds were reluctant to cross the bitter obstacle, and were slow to cross as they avoided touching the substance. But slowly they learned the substances were harmless, and after six days, they were crossing the bridge at the same speeds as the control group.

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Their learned tolerance was limited to the specific substance. A protist that had learned to wade through coffee was once again apprehensive when blocked by quinine. A two-day break from testing also erased the learning.

Researchers call this basic form of learning "habituation."

The experiment's results were published this week in the journal Proceedings of the Royal Society B.

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"Documenting learning in non-neural organisms such as slime molds is centrally important to a comprehensive, phylogenetic understanding of when and where in the tree of life the earliest manifestations of learning evolved," researchers wrote.

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