Please give your definition of "learning" first. We wondered about whether learning requires a nervous system or if there is evidence that metazoans without nervous systems might learn. Thanks!
This issue needs a serious analysis, including explanations of the concepts, mechanisms, conditions, regularities of the learning process at all stages of evolution. For example, poets figuratively say "and the stone feels and understands the pain." What is the basis of such poetic representations of Shakespeare, Shelley, Byron, Keats ...? "A thing of beaty is a joy for ever ..." A new genius is needed comparable to the Genius of Ivan Pavlov, who will comprehend this problem. There are two manuscripts on this subject in Attachment.