The theory of entoptic phenomena is simple : phosphenes (or entoptics) are generated in the neural system, and anyone can see them. These visions are enhanced by the taking of hallucinogenic drugs; these drugs may have been taken as part of a shamanistic ritual and the images "seen" were then drawn by the visionary.
Heinrich Klüver who, in 1926, noticed that hallucinations seemed to occur in two stages, the first being related to four types of geometric: the grid, described variously as lattice, filigree, honey comb, grating, fretwork and chessboard; cobwebs; tunnel, also associated with cone, vessel, funnel, alley; and spirals. The second stage was that of iconic images which Klüver interpreted as being drawn from memory. An interesting point is that there seemed to be constants of theme in the more elaborate iconic images, the most common being religious symbols and images, followed by images of small animals and human beings (Siegal, 1977).
"The long association during the Upper Palaeolithic of entoptic with often remarkably 'realistic' depictions, combinations of entoptic and iconic elements predicted by the neuropsychological model, the occasional combination of different iconic images... the location of much of the art in remote galleries and inaccessible diverticules..." and that these are "better explained by the more extreme varieties of altered consciousness than by infantile perception." (Lewis-Williams, 1991)
Another concern is that of sequence in time. Leroi-Gourhan (1968) divides Upper Palaeolithic art up into a chronology of styles. The 'signs' fit into this chronology and change over the progression. This change is not problematic for the iconic images since in Lewis-Williams and Dowson's theory they are largely culturally determined derivatives from the fundamental forms, but according to their theory the entoptics have their origin in the nervous system itself - they are fundamental universals and should not change as a function of time and style. Leroi-Gourhan said "At Lascaux I really believed they had come very close to an alphabet." (recalled by Brigitte Delluc and Gilles Delluc of the Musee de l'Homme, Paris, in Lewis-Williams and Dowson, 1988), and it is likely that early sign-alphabets would be indecipherable to all but those members of
the group that developed them, the ones who knew what they stood for.We've had a nervous system capable of hallucinating for millions of years, our hands have been free from the task of locomotion for millions of years, yet art doesn't appear until possibly 300,000 BP on the evidence of an engraved bone (Lewis-Williams and Dowson, 1988) and doesn't really blossom until the Upper Palaeolithic.
One of the characteristic properties of intoxication by hallucinogenic substances such as LSD and Mescaline is a tendency to spontaneously perceive regular geometrical forms. Heinrich Klüver (1966) has categorized certain types of patterns, or form constants, commonly observed under mescaline intoxication, which subjects described as lattice, fretwork, filigree, honeycomb, and chessboard patterns, as suggested in figure A, as well as cobwebs, tunnel and funnel patterns as suggested in figure B. These same form constants are also commonly observed under a wide variety of conditions of psychological stress, or threshold consciousness, including falling asleep, waking up, insulin hypoglycemia, the delerium of fever, epilepsy, psychotic episodes, advanced syphilis, sensory deprivation, photostimulation, electrical stimulation, crystal gazing, migraine headaches, dizziness and a variety of drug intoxications (Siegel 1976). The diversity of different conditions which provoke the same kinds of patterns suggests that these form constants reflect some fundamental property of the visual system.
Siegel (1976) observes that the visual patterns seen under LSD intoxication are strikingly similar to the primordial or archetypal forms such as the mandala, the mystic symbol of the universe employed in Hinduism and Buddhism as an aid to meditation. Moreover, as many anthropologists have noted, the hallucinogen-inspired art of many primitive peoples often contains similar geometrical patterns of form, color, and movement (Lewis-Williams & Dowson 1988). Actually, the same kinds of form constants also appear commonly in art which is not hallucinogen-inspired, most especially in the patterns of non- representational or decorative art and ornamental design. For although there is a great degree of variation in the arts of different cultures, there is also much that is common among them.
The world's oldest example of abstract art, dating back more than 70,000 years, has been found in a cave in South Africa. Supposely, "modern" human behaviour started only around 40,000 years ago. We can notice complex geometric patterns; a double-wave pattern.