Lecturer's Précis - Freud (1900)

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First published online 13:28 BST 6th May 2002, Copyright Derek J. Smith (Chartered Engineer). This version [2.1 - link to graphic] dated 09:00 BST 2nd July 2018

An earlier version of this material appeared in Smith (1999). It is reproduced here with minor amendments and supported with hyperlinks.


Sigmund Freud as Cognitive Modeler (Example Three of Five)

Read firstly Freud (1891) and Freud (1896).

Here is how the 1896 diagram had evolved in Freud's thinking by the time he wrote "The Interpretation of Dreams" in 1900. To see later developments still, click Freud (1923) or Freud (1933) as appropriate. Concluding remarks are given in the 1933 entry.

Freud's (1900) "Psy-Systems" Diagram: Here, from The Interpretation of Dreams, we have a set of slightly more adventurous early diagrams, this time showing both the perceptual and motor aspects of cognition.

Figure 1: Information is now regarded as flowing through a sequence of what Freud called "Y-systems", beginning (left) with the sensory apparatus and perception, Pcpt, and ending (right) with the motor apparatus, M.

Figure 2: Memory resources - shown as Mnem - are available to every one of these psy-systems except the first and the last, and it is within this succession of memories that "the basis of association" lies (p688). More significantly, given psychoanalysis's then emerging emphasis on the unconscious causation of behaviour, these memories remain unconscious until formally retrieved into consciousness, and those "which have had the greatest effect on us - those of our earliest youth - are precisely the ones which scarcely ever become conscious" (p689).

Figure 3: Finally, Freud adds in the preconscious and the unconscious. The preconscious, Pcs, allows the willed initiation of behaviour, whilst the unconscious, Ucs, has no access to consciousness except via the Pcs. A short circuit (long curved arrow, bottom) allows automatic reflex response.

The problem with left-to-right linear set-ups such as this is that the perceptual and motor aspects end up too far apart: this is set right in Freud (1923), which begins to adopt the omega shape used in Lichtheim's House and Wundt (1902).

If this diagram fails to load automatically, it may be accessed separately at



Redrawn from three separate figures in Freud (1900/1953:686-687;690). This version Copyright © 2002, Derek J. Smith.



Freud, S. (1900/1953). The Interpretation of Dreams. Harmondsworth: Penguin. [Being the Penguin edition of the 1953 Strachey translation of the German original.]

Smith, D.J. (1999). Freudian Structures in the Computational Mind: Some Lessons from the Study of Ritual Sacrifice. Cardiff: UWIC. [ISBN: 1900666111] [Transcript of paper presented 15th April 1999 to the 13th Annual Conference of the History and Philosophy of Psychology Section of the BPS, York.]