A major finding of cognitive psychology is that long-term memory depends on coherent hierarchical organization of content—chunks within chunks within chunks. A speaker’s challenge is to use the fundamentally one-dimensional medium of speech (one word after another) to convey a multidimensional (hierarchical and cross-linking) structure. A speaker begins with a web of ideas in his head, and by the very nature of language he has to convert it into a string of words.
