Scientists have discovered that a slime made up of independent, single cells, can "learn" to avoid irritants despite having no central nervous system. These results suggest that the hallmarks for learning can occur at the level of single cells.

See the source article by following the link below:
Scientists have discovered that a slime made up of independent, single cells, can "learn" to avoid irritants despite having no central nervous system. These results suggest that the hallmarks for learning can occur at the level of single cells.