<P> This experiment intended to show that memory could be transferred chemically . The experiment was repeated with mice, fish, and rats, but it always failed to produce the same results . The perceived explanation was that rather than memory being transferred to the other animals, it was the hormones in the ingested ground animals that changed the behavior . McConnell believed that this was evidence of a chemical basis for memory, which he identified as memory RNA . McConnell's results are now attributed to observer bias . No blinded experiment has ever reproduced his results of' maze - running' . Subsequent explanations of maze - running enhancements associated with cannibalism of trained planarian worms were that the untrained flatworms were only following tracks left on the dirty glassware rather than absorbing the memory of their fodder . </P> <P> In 2012, Tal Shomrat and Michael Levin have shown that planarians exhibit evidence of long - term memory retrieval after regenerating a new head . </P>

Nervous system and sensory structures of the planarian