Whoops! What was I thinking?!  I almost forgot to mention... "...There are many points of similarity between the more mature Freudian diagrams (the 1923/1933 versions) and the control hierarchy diagrams shown in, say, [...]Craik (1945). For example, both adopt a three-level control hierarchy wherein each level owes it to its neighbours to keep private as much of its processing as it can. But they differ, of course, in considering the motivation for this secrecy - a Freudian would see it as a matter of the psychosexual acceptability of the material concerned, whilst a control engineer would see it merely as a matter of efficiency or inefficiency. Either way, what emerges is a layer cake of qualitatively different memory types with quantitatively different rights of access to consciousness." http://www.smithsrisca.demon.co.uk/PSYfreud1933.html <{-;)