Metaphor of the Human Psyche
Jungian psychologists use the pyramid shape to illustrate stages in the development of the human psyche from immaturity to maturity. With its four sides and central apex, the pyramid is a model for archetypes (universal patterns in human behaviour).
Here is a quote from King, Warrior, Magician and Lover, by Robert Moore and Douglas Gillette. It explains how the pyramid metaphor can be used to illustrate aspects of masculine psychology.
"The four archetypes of boyhood, each with a triangular structure, can be put together to form a pyramid that depicts the structure of the boy's emerging identity, his immature masculine Self. The same is true of the structure of the mature masculine Self (...) the adult man does not lose his boyishness, and the archetypes that form boyhood's foundation do not go away. Since archetypes cannot disappear, the mature man transcends the masculine powers of boyhood, building upon them rather than demolishing them. The resulting structure of the mature masculine Self, therefore, is a pyramid over a pyramid (...) Though images should not be taken literally, we are arguing that pyramids are universal symbols of the human Self."
In a note on page 15, the authors state that the Self-structure in women is also pyramidal in form. When the pyramids of the masculine Self and the feminine Self are placed end to end, they represent the Jungian Self, which embraces both masculine and feminine qualities.