“In the first experiment, the slime moulds took 10 hours to cross the bridge and they really tried not to touch it,” Dussutour said. After two days, the slime moulds began to ignore the bitter substance, and after six days each group stopped responding to the deterrent.
The habituation that the slime moulds had learned was specific to the substance: Slime moulds that had habituated to caffeine were still reluctant to cross a bridge containing quinine, and vice versa. This showed that the organisms had learned to recognise a particular stimulus and to adjust their response to it, and not to push across bridges indiscriminately.
Finally, the scientists let the slime moulds rest for two days in situations where they were exposed to neither quinine nor caffeine, and then tested them with the noxious bridges again. “We saw that they recover — as they show avoidance again,” Dussutour said. The slime moulds had gone back to their original behaviour.
And then it gets really, really weird...
Unlike complex multicellular organisms, slime moulds can be cut into many pieces; once they’re put back together, they fuse and make a single giant slime mould, with veinlike tubes filled with fast-flowing cytoplasm forming between pieces as they connect. Dussutour cut her slime moulds into more than 4,000 pieces and trained half of them with salt — another substance that the organisms dislike, though not as strongly as quinine and caffeine. The team fused the assorted pieces in various combinations, mixing slime moulds habituated to salt with non-habituated ones. They then tested the new entities.
“We showed that when there was one habituated slime mould in the entity that we were forming, the entity was showing habituation,” she said. “So one slime mould would transfer this habituated response to the other.” The researchers then separated the different mould again after three hours — the time it took for all the veins of cytoplasm to form properly — and both parts still showed habituation. The organism had learned.
https://www.quantamagazine.org/slime-molds-remember-but-do-they-learn-20180709/
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