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The brain, weighing on average just around three pounds, has a complexity of structure and function that we are only just beginning to understand. Estimates vary, but we have around 100 billion neurons, which communicate via perhaps several hundred trillion synapses. The whole brain is awash in a swirl of neurochemicals, and lightning storms of electrical activity flicker across it, as millions of sensory signals from the eyes, ears, nose, mouth and skin are thrown into the mix.

It is a wonder we can even think. And yet we do. A linear processing machine bombarded with this flood of stimulation would probably shut right down. The brain is quite different. It somehow makes sense out of the welter of flashing signals. The human mind engages in daily magic tricks that make David Copperfield look like a parlor act. Studies in neuroscience indicate that the sense we make of external things is based in small part on what we see outside and in large part on the patterns located in our minds.


As Lewis Carroll demonstrated in the "brillig" and "slithy toves" of his poem Jabberwocky, it takes only a little bit of context for our marvelous sense-making abilities to draw meaning from absolute gibberish. With a little effort, the following statement, circulating online, should make this point clear. While neither the study nor the university are formally identified, the words, however garbled, speak for themselves:

Aoccdrnig to rscheearch at an Elingsh uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, olny taht the frist and lsat ltteres are at the rghit pcleas. The rset can be a toatl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae we do not raed ervey lteter by ilstef, but the wrod as a wlohe.

Ask yourself: Does the rest of your life have this many holes that you are not seeing?

The mind appears to do this, in part, by choosing to ignore some of the external world. American neurophysiologist Walter Freeman discovered that the neural activity due to sensory stimuli disappears in the cortex. Our eyes and ears are constantly gathering information, but our mind is not really processing all of it (see sidebar, "Mkanig Snese from Nsosnese"). This stimulation flows into the brain, where what seems to be an internally related pattern appears, which the brain uses to represent the external situation.

The brain takes in the information about the world through the senses and then discards most of it, using it principally to evoke a parallel world of its own. Each brain creates its own world, which is internally consistent and complete. Perception is not a linear process of information reception, processing, storage and recall. Instead it is a very complex, interactive, subjective and evocative process.

It is as if a visitor came to the front door and rang the bell, and the person inside, by a quick glance through the fisheye peephole, formed a complete profile of the person outside, without opening the door. We know from experience that we have the ability to form snap judgments about people immediately—and that these judgments are sometimes wrong. Yet this process is extraordinarily efficient and effective, which is why there are peepholes in doors in the first place. Unlike a baby first learning about the world, we don't have to try to make sense of every new piece of information. Given a few lines, we can fill in the entire image. This ability to respond intuitively to what we see is crucial to quick thinking and action. (In Chapter 10 we discuss the power and limitations of intuition.)

Building Our Brains

The brain has developed and changed throughout human evolution, and its layered structure clearly shows this, starting deep within with the oldest "reptilian" part and moving out through the "limbic" system to the "neocortex," the seat of rational behavior.

Our own brains change and evolve over time, with neurons constantly dying and being recreated, synapses being destroyed and created anew. The brain selects and reinforces or weakens certain synapses to forge the complex neural structures that determine our thinking. Then we reshape these neural "models" through experience, education and training.

The newborn child has a fundamental but only rudimentary capacity to make sense of the signals, probably derived from genetic instructions. Subsequent experience works upon this genetic foundation. The child's first, urgent task is to quickly develop the capacity to make sense of all these confusing signals. Within the first two years, most children appear to develop this capability. The process involved is to understand where the stimulus comes from and then categorize the signal as some specific case of a more general pattern. A mix of shadows and colors is recognized as a ball. The face hovering above the baby is recognized as the mother—but then all similar faces are also seen as mother until the model is refined. The child is able to form a holistic sense without getting bogged down in the details. This categorization is key. These experiences are also retained in the form of memory—complex patterns spread across the brain that are not representational but are evoked by other patterns and external stimuli.

As the internal worlds in the child's mind become richer, the external world recedes. Freeman's experiments show that the balance tips from the outside to the inside. The brain's own models replace the input signals from external sources. When the brain confronts a new experience, it calls up a complex neural activity or "mental model" that seems to be its nearest equivalent. We see the absence of these models in the child's wonder at the simplest of experiences. We feel their presence when we express regret about the familiar routines and ruts that sometimes determine our lives in adulthood. The development of mental models is, in a certain sense, a demarcation line between childhood and maturity. We increasingly live in a familiar world that can be considered as a benign illusion—benign, because it helps us move through the world efficiently, but an illusion nonetheless.

We eventually lose all awareness that these "models" are in fact internal illusions. We accept them as external reality and act on them as if they were. If they are good models, in most circumstances they more than adequately permit the mind to handle external reality. But here a danger creeps in. When the world changes in important ways, we can find ourselves with a model that is completely irrelevant to the current situation. We find ourselves wearing our street clothes when we are thrown off the deck of a ship. What we need at that point is a wet suit and lifejacket.

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