The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning (26 page)

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Authors: Daniel Bor

BOOK: The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning
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So, when pushed by challenging tasks, we can use our long-term memory as a crutch to convert the items in working memory into a more efficient form. The task becomes dramatically easier, our performance increases markedly, and the newly chunked information we store is more stable, robust, and efficient.
But in humans, especially, it’s not just mnemonic tricks and familiarity that can profoundly increase the actual information stored in our working memory. In the example above, the student improved his performance by artificially gluing these novel numbers to his preexisting structured knowledge about running times. He, in effect, forced patterns into unpatterned data. But often there really is a clear structure or pattern to the information streaming in from our senses, and in these situations our consciousness seems particularly alert to its detection—probably because such novel information promises significant improvements—and we can rapidly exploit this newfound knowledge.
There is good experimental evidence that we spot and successfully use any structure in sequences to aid working memory. For instance, sticking with the task of simply remembering sequences of digits, colleagues and I in Cambridge presented volunteers with novel sequences of four double digits, some of which had a hidden mathematical relationship between them, such as 49, 60, 71, 82 (so, increasing by 11 each time). Other sequences had a random spacing between items. As you’d expect, participants were considerably better at recalling the structured sequences than the random ones. Volunteers noticed the structure and found that the task became easier when there were discernible patterns, as if there had been fewer items to remember, precisely because they had found the rule that linked the digits together. Although we didn’t test this, we could have given subjects patterned sequences 300 digits long, and they probably still would have had no trouble recalling the sequences—all they would have needed to remember would have been the first number, the last, and the rule. In contrast, they would have utterly floundered with 300-digit-long random sequences on their first session, and even on their 200th session. Importantly, chunking by rules is usually far more effective than chunking by memory alone.
One classic area of expertise in working memory is that of chess. We novices may look at a board full of about thirty chess pieces in some complex position and be lucky if we remember a few of those pieces. Chess masters, however, can remember almost the whole board with just a look. How do they do this? Very probably they are using a combination of memory (say, remembering the position of the pawns because pawn structures tend to be diagonal), and logic (such as perceiving doubled rooks as a powerful push up a line toward the opposing king). Chess expertise is a good illustration of how memory, logic, and strategy can sometimes inextricably intertwine, with structured information at the core.
Indeed, with the contents of working memory allowed to be virtually anything, this conscious playground of ideas is at its most powerful when the contents themselves are goals or strategies: If each mental trick can be treated as a separate building block in consciousness, where it can be combined with others in order to generate novel, more potent strategies, an unrivaled potential for learning and understanding is unleashed.
So we may be biologically constrained to consciously store only a handful of items for a few seconds, but we are also able to use any trick in the book to dramatically increase the amount of information per item. This may involve employing relatively trivial tactics, such as repeating numbers to ourselves. But we might just as easily use grander strategies, such as linking large amounts of novel information to preestablished memory chunks, or noticing the logical rule that binds many unfamiliar items together into a more coherent single unit.
BELITTLING THE RICHNESS OF EXPERIENCES?
 
This is an appropriate point at which to pause and meet one obvious objection to the thesis that consciousness boils down to an attention-gated working memory, with up to four chunks making up its contents. If our consciousness is really limited to a small handful of highly processed items, then how can we at least appear to see many more objects at once? It certainly seems that if I gaze up at the sky, I can make out more than four objects—maybe hundreds more in one go, and I can see them all clearly.
But I would argue that in this situation, attention is spread wide and thin, like an overblown balloon. Its thinness means that we are indeed aware of these hundreds of objects, but in a minimal, approximate way. Gazing up at the sky without any knowledge of star charts is akin to seeing the whole collection of stars as one fuzzy, complex object. If we want to remember things better, if we want to start seeing groups of stars, and memorize their relationship to each other, then—guess what?—we develop chunks to help us. I recognize the Plough because it looks like a deep frying pan with a wonky handle. And that constellation is Leo, a proud lion resting on the savannah. Without these chunks of stars, linked to well-known objects in memory, we’d have struggled to recognize any astral features, and historically this would have been a disaster for both navigation and agriculture.
There is strong experimental confirmation of this sense that the more we see, the less we actually take in of each object. For instance, if we have to identify varying numbers of letters or digits, which flash briefly on the screen, then the greater the number, the less likely we are to identify each one. In fact, however many there are, we’re unlikely ever to remember more than four of them, even if we do get a vague sense of the approximate number of objects we’re seeing. And, as I’ve discussed, in whatever way we are looking at the world, with any sense or stimuli, we only ever are fully aware of about four objects. Any impression that we are aware of more items may simply be an illusion. This illusion is partly a product of our extreme readiness to group items together to take up a single working memory slot—for instance, the
collection
of all the visible stars that we are currently viewing.
Without grouping together or fully processing any items in very busy surroundings, we usually only have a vague, faint conscious impression of its details. For instance, occasionally we may catch only the briefest glimpse of a scene and just have a gist of the objects in it. Our sense of gist reflects the fact that attention has two clear stages: The first, meager, less interesting stage of attention, and indeed awareness, is where we get a weak sense of everything around us, as if we’re not really attending to anything—or rather, we are attending to everything in the same minimal way. This lasts for about 200 milliseconds. A short time later, though, the second form of attention kicks in, which is goal driven. Our neuronal landscape shapes itself according to the task at hand, and we start to hone in on interesting details—there’s my wife in the station, say.
During this second stage, our brains then calculate exactly what it is we want to focus on, what the few objects are that really matter. This important subset of our world gets a generous attentional boost, and we are far more aware of what matters. Everything else gets suppressed, and our awareness of whatever is outside our working memory and focus of attention may become invisible.
Scientists have seen the neural equivalent of this story firsthand in a part of the monkey brain that codes for visual objects. Known as the “inferotemporal cortex,” this region has certain neurons that fire strongly for one particular item—say, a flower—and weakly for another—maybe a mug. Leonardo Chelazzi and colleagues used electrodes to study these neurons, one by one, when a monkey was looking for a particular target object that would appear on the screen—such as the flower—to get a reward. Whether or not a given inferotemporal cortex neuron was responsive to flowers, it would initially peak in the same way, as if everything that the monkey was looking at was always provisionally interesting. Only after a few hundred milliseconds would the neuron show its true form. If the neuron wasn’t interested in flowers, its activity would die away, but if it was interested, then its activity would continue to climb strongly. So these neurons, at the business end of how the brain attentionally responds to stimuli, have a two-stage firing pattern—the first is like getting a faint gist of the scene, while the second is all about carrying out a goal, with neurons shaping their activity to reflect what’s important and what’s not.
In our sense of gist, there is no second stage, or rather, because the input was so weak and transitory, the second stage is merely a copy of the first stage, and so there is minimal or random shaping of the input. Consciousness is unfocused and can randomly, weakly recognize a handful of objects from that brief glance.
When we grasp the gist of a scene, imperfect as it is, nevertheless at least some attention has to be involved. We can show this by seeing what happens when we completely remove attention from that brief glance. Michael Cohen and colleagues recently carried out just such a task. Subjects watched a rapid stream of different images, which changed every 100 milliseconds. Most of the scenes were just boring color swatches, but one of them in the middle was an interesting real-life scene, say of a city view replete with many skyscrapers. If this was all the subjects had to do, then almost everyone at least noticed the scene and could answer basic, nonspecific questions about it, such as whether the scene was of a beach or a mountain. But if they simultaneously had to perform a very attentionally demanding task, such as keeping track of a set of moving objects superimposed on the images, then only 12 percent of the subjects noticed any scene whatsoever. This clearly shows that we need at least to allocate some attention in order even to get a weak impression of a scene.
And in fact, for any contents of awareness you’d care to name, including tremendously simple features—such as a colored dot, or the angle of a simple patch of grey—if you carefully and fully divert attention away from the feature, it fails to enter consciousness.
So attention is certainly a necessary gating component of consciousness, and while full consciousness of some detail means it has to be strongly attentionally favored as it firmly enters our limited working memory, the same working memory holder can weakly store an approximate group of items that we are faintly conscious of. Occasionally our entire working memory is even called upon to recreate a brief glimpse of a scene, but the lack of detailed analysis or pointed attention is reflected in our very imperfect awareness of the features in front of us.
CHUNKING AND CONSCIOUSNESS
 
Now returning to chunking, although this process can vastly increase the practical limits of working memory, it is not merely a faithful servant of working memory—instead it is the secret master of this online store, and the main purpose of consciousness.
So far I’ve argued that attention is the gatekeeper of awareness. Sometimes it chooses what enters consciousness because of pressing biological issues, such as a potential danger, and sometimes it chooses what enters based on a deliberate goal we have set ourselves. But whatever enters consciousness reflects a first guess, a provisional analysis, that this item is currently very relevant to us, based on our various needs. And the output of attention and the arena for consciousness is our working memory, which is limited to a maximum of about four or so items. But, crucially, all those objects are processed as deeply as our brains allow, and this makes every detail of every item available in a unified way. We are then free to apply various strategies to further examine the items, notice similarities and differences between them, combine them, swap them around, and so on. I’ve repeated the mantra throughout this book that consciousness is concerned with information—specifically, useful, structured information. Chunking is the main catalyst within the bubbling cauldron of working memory where we convert the raw dust of data into molten gold, where basic information from our senses joins the highly refined, hierarchical edifice of meaning that we’ve been building up from birth.
There are three straightforward sides to chunking processes—the search for chunks, the noticing and memorizing of those chunks, and the use of the chunks we’ve already built up. The main purpose of consciousness is to search for and discover these structured chunks of information within working memory, so that they can then be used efficiently and automatically, with minimal further input from consciousness.
 
First the search: Surprisingly, the straightforward result that working memory is limited to four items was only accepted relatively recently, at the turn of the twenty-first century. For the entire half century preceding this, most psychologists assumed that our working memory capacity was around double this, mainly because most researchers failed fully to acknowledge how ubiquitous human strategic processing is and how we all, as a matter of course, use these strategies to boost performance.
I have attended hundreds of research talks over the years, and at these seminars I’ve heard a particular complaint again and again. It can involve any lab, almost any kind of experiment, and any human population group: However tightly you try to control an experiment, if it poses any kind of challenge to the subjects, those pesky human volunteers will almost always find some strategy to improve performance, usually in a way that neatly makes the experiment invalid. Human innovation is not confined to inventions for revolutionary cyclonic vacuum cleaners and state-of-the-art tablet computers—it is happening almost all the time in all of us, whenever we are awake. Searching for and then finding useful strategies for solving problems, whether large or small, is a signature feature of consciousness.

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