DURING THE PERIOD I SPENT LIVING ALONE ON THE mountainside, I spent a lot of my time staring into the fire. I’d pile up some rocks in front of the lean-to for a fireplace, and would pass the evenings sitting on a log, gazing at the flickering flames, the multicolored embers shading from deep red to pure white. In a sort of semitrance, I observed images and sometimes whole scenes that were quite realistic—cities rising out of deserts, marching armies, a group of nuns strolling arm in arm, monkeys swinging from tree to tree. I knew that these things weren’t really there, but I also knew that I would not be seeing them if I weren’t staring into the fire. Somehow the shifting, flickering lights were stirring up visions inside my head. At times I would feel cut free from time—not a twentieth-century person, but simply a human, staring into the same fire humans have stared into for hundreds of thousands of years, seeing the same things. I got a powerful sense of how mysterious fire must have been to our ancient ancestors, and how entertaining—what need did they have for television when they had this constant source of images?

That a flickering light can cause mysterious and often entrancing visual hallucinations, then, is something humans have known since the discovery of fire. It must have been knowledge of great value to the ancient shamans and poets, who learned how to use the images in the flames to enhance their magic. Even the most ancient scientists were intrigued by this phenomenon. Around A.D. 200, Ptolemy noted that when he placed a spinning spoked wheel between an observer and the sun, at certain frequencies the spokes of the wheel appeared to become immobile or to move backward (something we’ve all experienced when as children we thrilled to the runaway stagecoach scenes in cowboy movies). Ptolemy also discovered that the flickering of the sunlight through the spokes of the spinning wheel could cause patterns and colors to appear before the eyes of the observer and could produce a feeling of lightheadedness and euphoria. In the nineteenth century, French psychologist Pierre Janet, the influential teacher of Sigmund Freud, noticed that when patients of theSalpetriereHospitalinPariswere exposed to flickering lights they experienced reductions in hysteria and increases in relaxation.

Modern scientists have tried to analyze this phenomenon, and have conducted their experiments with light sources more sophisticated than fire. The great neuroscientist W. Gray Walter carried out a series of experiments in the late forties and fifties in which he used an electronic stroboscopic device in combination with EEG equipment to send rhythmic light flashes into the eyes of the subjects at frequencies ranging from ten to twenty five flashes per second. He was started to find that the flickering  seemed to alter the brain-wave activity of the whole cortex instead of just the areas associated with vision. Wrote Walter, “The rhythmic series of flashes appear to be breaking down some of the physiologic barriers between different regions of the brain. This means the stimulus of flicker received by the visual projection area of the cortex was breaking bounds—its ripples were overflowing into other areas.” The subjective experiences of those receiving the flashes were even more intriguing: “Subjects reported lights like comets, ultra-unearthly colors, mental colors, not deep visual ones.”

One thing that was happening, Walter realized, though it did not explain the curious visual effects, was that the flickering lights were causing the EEGs of the subjects to change and take on the rhythm of the flashing light. This phenomenon had already been widely noted–almost from the moment the brainwave patterns of the EEG were first recorded in the late 1920s researchers had realized that photic (light) stimulation could alter the EEG. In 1934, scientists established not only that the EEG pattern could be changed by repetitive visual stimulation at a known frequency, but also that the brain would quickly respond by falling into the same frequency. This effect, known as entrainment or photic driving, is the visual equivalent of the audio-frequency-following response stumbled onto by Robert Monroe and others who subjected the brain to rhythmic sounds and found that the brain’s EEG pattern would assume the frequency of the sound.


In the 1960s, some British artists and American writer William Burroughs read of Walter’s experiments, were fascinated by the reports that visual entrainment at certain frequencies apparently caused visual hallucinations, and put together a simple device to make use of it. They called it the Dreammachine. As one of the inventors described it in the rousingly apocalyptic terms appropriate to that psychedelic era:

The Dreammachine . . . is a pierced cylinder, which whirls around a light source to produce stroboscopic “flicker” over the closed eyelids of the viewer. “Flicker” at precise rates per second produces radical change in the “alpha” or scanning rhythms of the brain as shown by electroencephalographic research. Subjects report dazzling lights of unearthly brilliance and color, developing in magnitude and complexity of pattern as long as the stimulation lasts. When the flicker is in phase with the subject’s alpha rhythms he sees extending areas of colored pattern which develop throughout the entire visual field, 360 degrees of hallucinatory vision in which constellations of images appear. Elaborate geometric constructions of incredible intricacy build up from multidimensional mosaic into living fireballs like the mandalas of Eastern mysticism or resolve momentarily into apparently individual images and powerfully dramatic scenes like brightly colored dreams. . . . “Flicker” is a threshold experience of induced experience produced by altering the speed of light to accommodate the maximum range of our alpha rhythms. “Flicker” creates a dazzling multiplicity of images in constantly altering relationships which makes the “collages” and “assemblages” of so-called “modern” art appear utterly ineffectual and slow. Art history is no longer being created. Art history as the enumeration of individual images ended with the direct introduction of light as the principal agents in the creation of images which have become infinitely multiple, complex and all-pervading. The comet is Light.64

Scientific interest in the flicker effect increase during the 1960s, and then blossomed in the early and middle 1970s with a burst of independent studies by researchers around the world.9, 53, 74, 111, 163, 242, 257, 275, 360, 374, 379 These reports repeatedly confirmed that rhythmic flashing lights rapidly entrained brain waves. However, the researchers went beyond mere verifying of photic entrainment and investigated what effects this photic entrainment might have on the subjects. What they discovered was surprising, exciting, and suggested that photic stimulation could be a powerful tool for improving the functioning of the mind and body. In independent studies, researchers discovered that:

–at certain frequencies (particularly in the alpha and theta ranges), the rhythmic flickers could alleviate anxiety during the period of stimulation;

–subjects who had received such stimulation reported long-lasting and substantial reductions in their anxiety;

–at those same frequencies, the flashing light induced in the subjects a state of deep physical relaxation and mental clarity;

–by using photic stimulation it was possible to “train” the brain to modify its EEG frequency;

–after such training the verbal-ability and verbal-performance IQ of the subjects was increased;

–at certain frequencies (again, in the alpha and theta ranges), the flashing light increased the hypnotizability and the suggestibility of the subjects;

–flickering lights could bring the two hemispheres of the brain into a state of greater coherence or synchronization;

–such coherence between the hemispheres is related to increased intellectual functioning;

–in children up to the age of about fourteen, the most commonly produced frequency is theta, while for adults, the most commonly produced frequency is beta–that is, the percent of theta in the normal EEG decreases and the amount of beta increases as an individual grows into adulthood–and thus by entraining adults’ brain waves at a theta frequency it is possible to return an adult to a freer, more childlike mental state, characterized by vivid spontaneous mental imagery and imaginative, creative thinking.

While this flurry of studies about photic driving of the brain waves was going on, other researchers were investigating auditory driving of brain waves. By monitoring the brain with EEGs while stimulating it with sound such as rhythmic clicks, tones, or pulsations of white noise, they found that the brain did respond to rhythmic auditory stimulation with increased brainwave activity at the same frequency as the sounds. That is, using rhythmic sounds alone it was possible to entrain brain-wave activity, although the entrainment effects of sound alone did not appear to be as pronounced or long-lasting as the entrainment effects of light. It was also discovered that, as with photic driving, auditory driving showed evidence of brining the two hemispheres of the brain into a state of greater coherence or synchronization.

And while these separate studies of photic and auditory driving were being done, other researchers, as mentioned earlier, were discovering the existence of hemispheric synchronization and realizing that it was a state associated with a variety of benefits, such as deep relaxation, euphoria, and enhanced creativity and intellectual functioning.

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