The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning (21 page)
Authors: Daniel Bor
BOOK: The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning
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“Pardon me, my dear, but do you happen to know where the Wieners have mov—?”
“That’s okay, Daddy. Mummy sent me to fetch you.”
ATTENTION FUNNELING RAW DATA TO BUILD EXPERIENCESSo far in this book we’ve arrived at the position where consciousness is a physical, brain-based process, most effectively investigated by science. While information processing and the management of ideas is at the heart of evolution, the extra, far more capable forms of information processing inside a brain allow consciousness to emerge from this exquisitely designed biological computer. But awareness doesn’t arise in all species, or even at every moment in human life. In those species with the capacity for consciousness, low-level processing or routine actions are carried out unconsciously. Only when our data processing is of a sufficient magnitude and complexity, and of a certain type, does consciousness occur.
This and the next chapter will continue exploring exactly what forms of complexity, and what type of information processing, relate to consciousness, and how attention funnels the raw data we soak up from the world and converts a small portion of our input into the experiences that fill our lives with meaning. In this chapter I’ll be centering on the psychology of consciousness, and in the next on how the brain creates our experiences.
As my stories about absentmindedness illustrate, attention is closely related to awareness: What I attend to is what I’m conscious of, and whatever falls outside of my attention is processed, if at all, by my unconscious mind alone.
But before describing the intricate psychological details of what attention is, and how it relates to awareness, I will pause and ask, from first principles, what the purpose of attention might be.
Attention addresses a basic data-processing issue that almost all types of computers face. Simple information-processing systems, such as plants or bacteria, are receiving only a faint trickle of information from their senses and have only a rudimentary ability to process that information. On the whole, all the information they receive, they process as far as they can. But for more complex systems, where the information stream flowing in is overwhelming the system’s ability to process every item fully, there needs to be some decision process about which subset of all this mountain of data is most deserving of further analysis, and which other subsets are best ignored. This data-filtering and -boosting mechanism is attention.
At the extreme end of this continuum of information input and analysis capabilities sits the human brain, with enormous cortical regions capable of very deep analysis. Hence the necessity for highly aggressive attentional filtering and boosting. This filtering can be so intense and focused, for instance, that we can foolishly walk for 30 minutes and hardly notice our surroundings at all.
Human eyes have around 100 million photoreceptors, each of which can pick up about ten visual events every second, so our eyes are effectively receiving a billion pieces of information each second. If you include the information pouring in from our other senses, that’s a staggering quantity of data for our brains to sift through every moment of our waking lives. This weight of input is hardly unique in the animal kingdom—after all, many mammals have senses at least as acute as ours. But humans come up trumps from the analysis point of view, as, relative to the rest of our brains, we have considerably more general-purpose neural real estate by which to carry out detailed processing on the data we receive. This creates a dizzying potential for learning. And, as our everyday lives illustrate—and the fruits of science and technology reinforce in a muscular way—the deepest, most forensic analyses tend be the ones that offer the most rewards.
If we had an infinite source of energy by which to crunch the numbers, and an infinitely fast brain by which to make the calculations, then there would be no problem, as we could analyze every scrap of data to its fullest capacity and never miss an opportunity or be caught by a threat. But of course, in reality, it takes time to process anything, and human brains consume a frighteningly large proportion of our body’s total energy resources.
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So we have to be ruthless in what we filter out, and tremendously picky about what data we allow through to the highest levels of processing.
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So we have to be ruthless in what we filter out, and tremendously picky about what data we allow through to the highest levels of processing.
One key question here is just how you know what is biologically relevant. Imagine that there’s a poisonous snake near a plentiful food supply. An animal walks toward the food, and then quickly, effectively, its attentional system focuses in on the snake and little else. It recognizes the danger and flees. This has potentially saved the animal’s life. But what if the snake were dead, and the animal were starving, with little other food around? If greater analysis could have revealed the snake to be no longer a threat, perhaps by smell, or, in the case of particularly smart animals, a tentative poke with a finger or stick, then the animal’s life might have been saved by this extra understanding, which prevents it from running away and enables it to eat the food in this location.
This example shows that, ideally, you need an attentional system that is guided closely by various emotional and instinctive signals so that it can automatically—and quickly—focus in on any immediate threat. If threats aren’t present, then attention should choose to center on other vital biological needs: food, procreation, social status, and so on.
But
for all these drives, there may be a better, slightly more lateral step to achieve them, if only we understood the situation a little more deeply.
But
for all these drives, there may be a better, slightly more lateral step to achieve them, if only we understood the situation a little more deeply.
In a broad sense, because of these potential alternate routes to optimization, almost everything could be biologically relevant, potentially, and if you have enough brain resources, why not explore the informational terrain extensively? Humans thus readily attend not only to local external events, such as dead snakes, but to more abstract ones, too, such as the movement of the stars, or the factors that help crops grow, as well as to the internal information stream—for instance, an inner monologue about book compositions. Although such subjects have little to do with direct survival, on the surface, we continue attending
just in case
a deeper analysis reveals that they may assist us, if only we could reveal some hidden spark of wisdom from them. After all, our universally curious natures occasionally do strike gold, as exemplified by science and all of its technological products, which have made it so much easier for us to meet our basic survival needs.
NOT SPOTTING THE WOOD, THE TREES, THE BIRDS, THE SOIL, THE FLOWERS, THE . . .just in case
a deeper analysis reveals that they may assist us, if only we could reveal some hidden spark of wisdom from them. After all, our universally curious natures occasionally do strike gold, as exemplified by science and all of its technological products, which have made it so much easier for us to meet our basic survival needs.
In my embarrassingly blind walk described at the start of this chapter, it felt to me that attention was the gateway to my awareness—without attention directed toward some feature of the world, I simply would not be aware of it. This intuition has been repeatedly demonstrated in psychological experiments.
The first, commonly referred to as “change blindness,” is perhaps one of the most striking and important experiments in either attention or consciousness, and reveals almost all key features of both (see
Figure 5
for an example). Its standard form, first carried out by Ronald Rensink and colleagues, involves two photos identical except for one feature. These are presented to the volunteer on a computer monitor, with a blank screen sandwiched in between for about 80 milliseconds. When I tried this experiment some years back, in a large seminar at an academic conference, both pictures were of a military plane at an airport. With lots of flicking back and forth between pictures, I was initially convinced that the experimenter had made a mistake and that the two pictures were in fact identical. It didn’t help that the speaker, Bob Desimone, a world leader in the neuroscience of attention, cheekily suggested that the faster you spotted the change, the higher your IQ (to my relief, this isn’t true!). It took me and most of the audience a long time—perhaps 30 seconds—before we noticed that one of the pictures showed the plane missing an entire engine. My attention, heavily influenced by my expectations of what was important in the picture, was moving from interesting feature to interesting feature, such as the national insignia that identified the plane, the soldiers in the foreground, at the plane exit, or coming down the stairway, and so on. It simply didn’t occur to me to direct my attention to the engines, as you don’t expect planes on runways to lack these.
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And because I couldn’t attend to more than around a few items for each of the two pictures, I never had a chance to notice the change. This staggering delay to spot obvious, blatant differences between viewings is common, and another example of how limited the scope of our attention—and awareness—can be.
Figure 5
for an example). Its standard form, first carried out by Ronald Rensink and colleagues, involves two photos identical except for one feature. These are presented to the volunteer on a computer monitor, with a blank screen sandwiched in between for about 80 milliseconds. When I tried this experiment some years back, in a large seminar at an academic conference, both pictures were of a military plane at an airport. With lots of flicking back and forth between pictures, I was initially convinced that the experimenter had made a mistake and that the two pictures were in fact identical. It didn’t help that the speaker, Bob Desimone, a world leader in the neuroscience of attention, cheekily suggested that the faster you spotted the change, the higher your IQ (to my relief, this isn’t true!). It took me and most of the audience a long time—perhaps 30 seconds—before we noticed that one of the pictures showed the plane missing an entire engine. My attention, heavily influenced by my expectations of what was important in the picture, was moving from interesting feature to interesting feature, such as the national insignia that identified the plane, the soldiers in the foreground, at the plane exit, or coming down the stairway, and so on. It simply didn’t occur to me to direct my attention to the engines, as you don’t expect planes on runways to lack these.
15
And because I couldn’t attend to more than around a few items for each of the two pictures, I never had a chance to notice the change. This staggering delay to spot obvious, blatant differences between viewings is common, and another example of how limited the scope of our attention—and awareness—can be.
A real-world version of this experiment, by Daniel Simons and Daniel Levin, shows even more dramatic results. Unwitting volunteers walking on paths in the university campus are asked by one experimenter for directions to a certain building. A map is produced, which the volunteer helpfully starts examining to work out the best route to the building. Rather rudely, a door is then briefly passed in between these two people by two other secret experimenters, and the person asking for directions is swapped with someone else. This new person is holding an identical map and continues asking for directions as if nothing has changed. Incredibly, despite the fact that the new person has a different face, voice, clothes, and so on, less than half the volunteers notice that the person has changed.
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They are presumably so busy attending instead to their inner spatial worlds, as they work out the best route to advise the passerby, that they fail to attend properly to the man—or rather men—holding the map. And without attending adequately, they aren’t aware of the change. In some ways this is the experimental crystallization of absentmindedness—a trait I far too readily demonstrate, for instance, when I attempt in vain to go on walks to Byron’s Pool, or Weiner exhibited by being so distracted as to fail to recognize his own daughter.
16
They are presumably so busy attending instead to their inner spatial worlds, as they work out the best route to advise the passerby, that they fail to attend properly to the man—or rather men—holding the map. And without attending adequately, they aren’t aware of the change. In some ways this is the experimental crystallization of absentmindedness—a trait I far too readily demonstrate, for instance, when I attempt in vain to go on walks to Byron’s Pool, or Weiner exhibited by being so distracted as to fail to recognize his own daughter.
It isn’t merely changes that are missed if our attention is elsewhere, but also obvious anomalies in the world. In another famous attention experiment, known as inattentional blindness, originally carried out again by Daniel Simons and this time Christopher Chabris, volunteers watch a video of people playing with a basketball, the task being to keep a careful count of the number of passes. At some point in the video, someone slowly walks through the basketball players wearing a full-body gorilla outfit. Amazingly, only 44 percent of people actually notice the gorilla, despite the fact that it was in the video for a good 5 seconds, even pausing in the middle of the shot to face the camera and comically beat its chest.
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Again, because people are deeply attending to something else—in this case the basketball passes, as well as their internal tally of these passes—they don’t attend to, and aren’t in any way aware of, the mock gorilla invading the scene. Such black holes in our awareness are bread and butter for pickpockets and magicians, who are experts at manipulating our minds so that we fail to attend to the loci of their tricks.
17
Again, because people are deeply attending to something else—in this case the basketball passes, as well as their internal tally of these passes—they don’t attend to, and aren’t in any way aware of, the mock gorilla invading the scene. Such black holes in our awareness are bread and butter for pickpockets and magicians, who are experts at manipulating our minds so that we fail to attend to the loci of their tricks.
In all these instances, the story is the same: What we attend to equates with what we are aware of, and the boundaries of consciousness are extremely tight compared to the broad scope of stimuli entering our senses. This small subset of the world that we are actually aware of allows us to miss striking changes in a scene, or highly unexpected events occurring right in front of us. But the flipside of this phenomenon is that it helps us understand a few features of the world far more deeply than we would otherwise, and potentially to perform complex tasks in relation to them.
A BRIGHTER, MORE VIBRANT WORLDSo there is clear experimental evidence for the suggestion that we engage in tremendously aggressive attentional filtering in order to focus our awareness on a small component of our informational world. But what about empirical support for the second feature of attention, that it also acts to boost information processing?
If I’m trying to spot my wife in a crowded train station, I know she’s wearing a red sweater and that she has black hair, so I concentrate on scanning all the people for red sweaters and black hair, and then, if I find a partial match, I look for her facial features. When I do this, it feels as if I’m barely aware of the sounds around me, but every red item of clothing or head full of black hair stands out vibrantly. My whole mind seems attuned to redness, as if other colors are only important at that moment in a negative sense, because they are not red.
There is good experimental evidence to back up my impression that this controlled, directed attention is capable of actually enhancing both information processing and one’s awareness of certain features of the world. This is trivially true when attention causes me to move my eyes toward some object of interest, thus allowing the central part of my visual field, the fovea, to focus on the item. The fovea has a particularly dense collection of photoreceptors and considerably more acute resolution than my peripheral vision. So the simple act of moving my eyes and focusing on an object allows a far higher, richer stream of visual information to be absorbed than if I wasn’t looking directly at the object. Of course, once an animal has oriented toward an object, it tends to stare at it, soaking up the greater stream of input so that it can analyze more carefully what the object is, and thus further boost its processing of the information it is collecting for that object.
But you don’t have to be looking anywhere near the object for the boost to occur. For instance, consider the following experiment. Say you are required always to stare at a dot in the center of a computer screen. On half the trials, an additional dot will then randomly appear very briefly near one of the four corners, while on the other trials there will be no such peripheral dot. When this dot does appear, you really pay attention to it in your peripheral vision, because you know from the task rules that this corner dot is warning you that a difficult-to-detect, very faint object is about to turn up in that location—and the whole purpose of the experiment is to notice these faint objects. So even though you are constantly staring at the central dot on the screen, as instructed by the experimenter, you somehow shift your attention to this quarter of space, to prepare for the difficult-to-see object that’s about to appear. If you’re ready and attending in advance to this quadrant, then, for this quadrant and this alone, your vision actually improves—you are conscious of fainter targets than normal, objects you wouldn’t normally have seen, and you can also detect targets faster.
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