Lab research shows that humans typically move through three stages when entering a trance. In the first stage, the nervous system generates images of luminous, pulsating, revolving, and constantly shifting geometric patterns known as entopic phenomena–similar to images seen during a migraine headache. Typically these include dots, zigzags, grids, filigrees, nested curves, and parallel lines, often in a spiral pattern.
In the second stage, the brain tries to make sense of these abstract forms (a process known as construal). Here, cultural influences come into play, so a trancing Bushman in southern Africa’s Kalahari is likely to construe a grid pattern as markings on the skin of a giraffe, nested curves as a honeycomb (honey is a Bush delicacy), and so forth. A New York police officer or a Chinese priest would construe the patterns in very different ways.
During the third and deepest trance stage, people tend to feel as if they are one with their visions, passing into a rotating tunnel or vortex. Typically, the tunnel has latticelike sides where iconic images of animals, humans, and monsters appear, merging with the entopic forms of the earlier trance stages. Because these images are culture specific, individuals usually see things that have high significance within their culture.