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Why Our Brain Craves Random Noise

Credit: RyanJLane/iStockphoto

Credit: RyanJLane/iStockphoto

By John L. Bradshaw

Sensory deprivation, dreams, hallucinations and the detection of familiar patterns in clouds and repetitive sounds reveal our brain’s determination to make meaning from random noise.

In the 1960s, space was all the rage. We could fly folk to the Moon, but could we send spaceships further afield to film the planets? How would spacemen cope with a weightless state, and possibly very lengthy periods with greatly attenuated sensory input?

To address such issues, student volunteers were employed to spend lengthy periods in total sensory isolation, seemingly in blissfully relaxed comfort, and were paid to do absolutely nothing! They lay upon the softest substrates imaginable and achievable, in complete darkness and silence, insulated from any possible or conceivable sounds or tactile stimulation except those originating from within their own bodies – cardiac, respiratory, bowel, etc.

But they hated it! In a surprisingly short time, many started to experience vivid visual hallucinations, often of a weird nature, such as lines of little green figures advancing across their putative field of view. One participant even required hospitalisation from his experiences, and several demanded immediate release.

Parallels were to be drawn from the effects of psychedelic drugs, which were being tried, experimentally and for “recreational” purposes, in those halcyon and innocent days of the “Swinging 60s”. Dreaming (expecially nightmares) may be an everyday parallel of the effects of reduced sensory input and the apparent need to maintain experiences at a minimum level or, failing that, to generate one’s own.

So it seemed that we crave stimulation, and in its absence we may create our own cinema of the mind, conjuring ordered, if often puzzling, images out of nothing.

Blindness can be a frightening experience for someone used to normal vision. When the elderly lose their sight, they sometimes report the appearance of complex visual hallucinations; the Charles Bonnet syndrome was named eponymously after the first person to describe it in 1760. My own very aged mother-in-law used to be “visited” in her aged-care residence by splendid red fire engines of the type common in her youth, fully equipped with every fine detail. However, the ever-rational old lady recognised their hallucinatory nature, and settled down to watch the “show”.

As children, how many of us have lain in the grass on a hot summer day, watching the clouds float past and seen representations of faces, shapes and figures seemingly appear in them? Or, as adults, driving through a rocky gorge and been struck by the apparent outline of, say, Queen Victoria’s unique profile, or around the evening embers of a dying campfire seen the apparent rise and fall of castles or buildings? Such apophenia or pareidolia (the two labels are practically synonymous for the present purposes) are further examples of effort after meaning, an attempt to make sense of, to reduce the entropy of, largely random visual input.

If we listen to a nonsense “word”, such as “blig”, continuously and fairly rapidly repeated on an endless tape loop, after a while we may begin to imagine that we hear the repetition of some similar, real word, or even a short and simple message. The endless repetition of two words such as “fat dog, fat dog...” may eventually seem to morph into nonsense, or change into two different words. Even the steady “tick tock, tick tock...” of the family clock may eventually seem to be repeating a two-word message like “not now, not now” but on another occasion may appear to change instead to something else like “yes please, yes please”.

We may even need the presence of some adventitious or seemingly irrelevant “noise” to perceive or apprehend a message clearly. Consider an apparently simple task, such as flashing either a “v” or an “n”, so rapidly that mistakes in reporting which letter it was are likely made. The task is easier, fewer mistakes are made and even briefer flashes are tolerated if the two test letters are embedded in two words such as “dove” and “done”, even though the other letters “d”, “o” and “e” are entirely redundant and quite uninformative.

If, by an appropriate arrangement of lenses and mirrors linked electronically to your eye movements, you stabilise any image on the retina from the normal slight jiggling caused by the eye’s usual physiological or essential tremor, you don’t get a sharper image. Rather, that image very rapidly fades, losing all contours and discontinuities. It seems that the slight jitter, moving contours on and off each tiny retinal receptor, is needed to prevent an otherwise very rapid retinal saturation and loss of signal. We need a little noise, randomness, unpredictability, or change in stimulation for efficient perceptual function.

An even older and yet more basic example of the above principle involves the presentation, via goggles spanning the entire visual field, of a single, unbroken colour display, say a uniform pink or green without any contours, discontinuities or changes. Such a “ganzfeld”, as it is known, again very rapidly saturates to a colourless uniformity.

Conversely, detune a TV screen to produce “snow”, visual “white noise”, tiny dots continuously and randomly appearing, disappearing, changing over the entire screen. If you fixedly stare at it for a while, you may begin to see moving patterns, contours, discontinuities or even hints of faint moving figures, thereby apparently somewhat reducing the entropy, randomness or “uncertainty”. Likewise, when some people hear coarse “white noise” (sounding like a boiling pot) via earphones they may begin to hear words or phrases faintly. We fabricate meaningful patterns in the continued presence of random input.

After a long day typing, or staring at the computer screen, when I close my eyes I often see fragments of letters, groups of letters or even whole words appearing and disappearing. Likewise, after reading an Italian, French or Spanish novel, and turning to some other less-cerebral task, I often seem to hear snatches of phrases in that language. Sometimes, while “dropping off” just before sleep, I hear meaningless but grammatically correct phrases. Similar phenomena may occur at the transition from sleep to wakefulness. These phenomena, randomly accessed material from obscure memory stores, may be benign versions of the “commands” or “voices” commonly reported by individuals suffering from schizophrenia.

As a child, I remember happy autumnal days spent searching the woods for blackberries to eat. Later, through closed eyelids in bed, I would vividly see the outlines of the precious fruit. Again, in the absence of extraneous and changing visual input, we generate our own.

We even tend to see, or hear, what we expect to see or hear. Conversely, sharp deviations from what we expect to see or hear either stick out like the proverbial sore thumb or instead are completely missed and replaced by whatever is usual, predictable or to be expected, such as occurs with proofreading errors. Indeed, small, local retinal damage is often unnoticed, and if any of us look at patterned wallpaper we don’t notice a “hole” corresponding to where our blind spot is located on the retina.

Our physiology seems best to operate at a sweet spot or area, between the randomly chaotic and the finely ordered, regular and predictable. One might expect that an electrocardiogram that is completely regular might indicate better overall cardiac health than one with occasional irregularities, missed, double or ectopic beats. However, epidemiological evidence suggests that those of us with slightly irregular heartbeats tend to experience better overall cardiac health than those with faultless cardiac rhythmicity.

And what about the electroencephalogram (EEG), the seismological-like pattern of brain wave activity? Large, slow and regularly cycling brainwave patterns are not associated with aroused or finely focused attention and a period of dedicated thought, reflection or problem-solving. In the latter instance we typically see rapid, small-amplitude and seemingly random activity, probably reflecting many simultaneously active regions, circuits or subprocessors. Thus the more predictable, large-amplitude, regular and organised the EEG pattern, the less likely that the individual is awake or conscious; the more rapid and apparently disorganised and seemingly random the pattern, the more likely that the person is maximally engaged cognitively.

The greater the structural and functional interconnectivity in any complex information-processing system like our brains, and possibly like future artificial intelligence systems, the more likely it is that the neural or AI system will be conscious, to be considered conscious, or potentially able to achieve a level of conscious awareness. The overall EEG or its electronic equivalent would be seemingly disorganised as a consequence of massive amounts of local activity, all operating in parallel throughout the system, and all receiving input and generating output at different times and in different places.

A system exhibiting waxing and waning synchronous activity will probably be either grossly inefficient or faulty. Too much interconnectivity and randomly accessed thoughts, ideas or memories may be disruptive, as in schizophrenia, where such individuals or their genetically close relatives may tend to score highly on indices of creativity or achievements in the arts or sciences. The unpredictable can be exciting or frightening, while monotony can be boring or reassuring.

Is there a useful parallel, with recent findings relating to sterile environments and subsequent health? We all contain within us countless millions of gut bacteria, some “good”, some not so. Yet increasingly there is evidence that being reared in a sterile environment in the absence of a varied gut biome can be deleterious to subsequent health, particularly but not exclusively in terms of immunological function in later life. Asthma, whose incidence has risen enormously in recent years in advanced economies where hygiene is prioritised and practised, is only one of a widening range of immunological dysfunctions. We have evolved to accommodate a highly varied environment with many potential threats to our health; a uniform, unchanging and unchallenging background is not always appropriate or optimal in the context of developing allergies, haematological cancers, leukaemia and possibly even depression and Parkinson’s disease.

At an aesthetic level, more individuals are finding that they prefer the old vinyl LP records for their perceived acoustic qualities, warts and all, compared with more acoustically “clean” CDs. A well painted portrait, again with occasionally and deliberately blurred contours, or even one done in the pointillist or impressionist style, somehow seems more appealing and even lifelike than an optically perfect picture or photo.

Music buffs note that the appeal of a piece is partly related to the predictabilities of each successive note or cluster. If it’s largely or entirely predictable it may be considered boring, but if it is completely random it is disturbing, discordant or at least generally unattractive – it is no longer music.

Surprises can be positive and pleasing; indeed the basis of the typical joke is a punchline that deviates from the expected or normal. Too much of a deviation and it falls flat; too predictable, as maybe occurs in some puns, and we groan.

A bit of noisy randomness “never did no one no harm”.


John L. Bradshaw is Emeritus Professor (Neuropsychology) in the Monash Institute of Cognitive and Clinical Neurosciences.