Searching has turned up several pop sci articles that tell me that slime molds can anticipate periodic events. But I can’t find anything that explains how they do so. Do we just not know at all? Or am I not looking in the right place?
The paper linked in the article supposes that the cells contain a lot of internal oscillators that begin to arrange themselves based on repeated events. That part gives them memory. It’s not clear to me if there’s an explanation for the ability to react other than that, but the implication is that a stimulus is ‘recognized’ in the alignment of oscillators triggering a reaction.