A third possibility is that in the organic mental disorders - those involving brain malfunction - individuals revert to early stages of human evolutionary development.
The images created by such persons might be based on primordial impressions preserved in the so-called "collective unconscious."
Hence, their art is not necessarily defective; it merely reflects archaic ways of seeing.
Perhaps this imagery was once important from the standpoint of survival.
In the case of brain-damaged individuals, they may see the world through cracked lenses, but it is also possible that their art permits us to witness the thinking of creatures somewhat like ourselves, who lived before the dawn of history.