Ey up Hob!
< because our modern brains develop in a world full of 'un-natural' visual stimulus ... as we grow through childhood, our visual cortex develops differently from the way in which that of prehistoric people's did. >
Certainly seems that if the introductory psychedelic visuals are owt to go by. As the ventures begin, I get teddy-bears, sweet-wrappers and other 2-5yr old images emerging - nay streaming from my unconscious. Eventually this gives way to ego-obliteration and the arising of the Journey, so to speak.
If we go back a coupla thousand years or so, when people lived outdoors they were always close to water. And as many of us on TMA know, when we're in the hills for several days or more, we find ourselves staying close to water for the same reason as our ancestors did. And then, sitting by such places, there is a gradual subsumation of the ego as we gaze, either into the motions of the water itself, or else into Nature's background, with the sound of the waters as our music. (stay with this, please....!)
In the motions of streams and pools are the usual ripples and spirals: patterns we see unfold in many other places in Nature - but water seems to have a greater propensity to elicit such shapes than other natural ingredients. And water has a tendency to send us away a little bit - dreaming, so to speak. In innumerable cases from people all over the place, water has even powerful altered states of consciousness. So not only is it the 'blood' of the Earth itself, feeding us daily, it also has a very powerful ability to affect changes in consciousness.
I for one think that some of our rock-art relates to the primary patterns our ancestors saw in Nature and they gave these shapes particular meanings.
Now throw in the old shamans, consuming mushrooms, or smoking henbane, chewing hemp - whatever their preference. In the introductory images which unfold before the real visionary Journey begins, their forms are very likely gonna be images straight from Nature's heartland: shapes in water, tree-figures, animal forms, ideas of wind and spirit. Certainly not teddy-bears or other unnatural motifs.
Mix the ASCs of water with the visionary qualities and tricks of light in a mind where the ego is much more subsumed, and we have a marvellous emergent mythic structure unfolding. But I'd better shut up now, otherwise I'll be waffling transpersonal bollox!
...& Hob - that avatar's a picture of me done by a friend during a rather memorable ASC, many moons ago.
