Human: The Science Behind What Makes Us Unique - Michael S. Gazzaniga (2008)
Part III. THE GLORY OF BEING HUMAN
Chapter 8. IS ANYBODY THERE?
As the brain changes are continuous, so do all these consciousnesses melt into each other like dissolving views. Properly they are but one protracted consciousness, one unbroken stream.
—William James, The Principles of Psychology, 1890
EVER SINCE MY DAYS IN COLLEGE, I HAVE PUZZLED OVER THE problem of conscious awareness. This isn’t a story about college bull sessions dealing with the meaning of life. This is a story about my being fascinated with my college buddies. You see, I was a member of the fabled Animal House at Dartmouth College, and I was Giraffe. What a ride that was.
Actually, I was pretty square until Green Key Weekend of my junior year. I had a deal with my father. No booze until twenty-one and he would write me a check for five hundred bucks. But my frat brothers told me a great drink was grapefruit juice and vodka. So, emboldened with the idea of the moment, I dove into my first drink. It was a hot day, and about five drinks later, I declared there wasn’t much to this drinking thing, stood up from the sofa, took one step, and passed out.
Of course, the real lesson was about changing the normal conscious state of a twenty-year-old. Why do we love to change our consciousness, our appreciation and feelings about the world around us? We drink, we smoke, we do lattes, we seek painkillers, we may even get runner’s high. We are always tampering with an aspect of our existence we still can’t define: phenomenal conscious experience.
Consciousness comes in many flavors. Anyone who has taught an introductory college class, or attended one at eight o’clock Friday morning, has seen them all. There may be a couple of party-hearty frat boys in the back row, dozing after a long night spent celebrating the upcoming weekend. These two are not conscious. Up a couple of rows is the scammer checking out the hot babe across the aisle and wondering if he can get a date. He is conscious, but not of you; nor are the three girls down the way who are passing notes to each other and suppressing their merriment. Another has a tape recorder going and is finishing up a paper for another class, and will be conscious of you later. The front-row kids are sippin’ their coffee, taking notes furiously and occasionally nodding in agreement; at least they are conscious of you. Although most people don’t sit around and ponder the question of consciousness, they talk about it a lot. After class you may overhear: “I finally realized [was conscious of ] what a jerk he was, like, he totally didn’t even pay any attention to what I was saying and was only conscious of the sports channel. Great if you are into football stats, but if you want him to [be conscious of and] remember your birthday, forget about it. I, like, totally dumped him.”
We have talked a lot about two aspects of brain function: the nonconscious goings on and the conscious goings on, the latter being what researcher Michael Posner at the University of Oregon calls alertness. We have already seen that a considerable amount of processing, one might even want to say most of it, occurs without our being aware of it: undercover. It hasn’t been easy figuring out the content of all the nonconscious goings on that have been elucidated so far, for the simple reason that it doesn’t bubble up to our consciousness. Researchers have had to devise tricky experiments to reveal their presence.
This might lead one to think that studying consciousness may be a little easier. Yet, as French neuroscientists Stan Dehaene and Lionel Naccache point out, the object of our study is now introspective and not an objectively measurable response.1 Oddly enough, subjective reports of introspection themselves give us some clues. My studies with split-brain patients have revealed that introspection can be wrong.2 We actually unwittingly make up stories to fit the observable phenomenon, but this very fact is also a clue, which we will look into a bit later. Our very dualistic nature has also been a stumbling block on the road to unlocking the mechanisms of consciousness.3There are those who feel that the essence of consciousness cannot have a physical explanation, that it is so wondrous that it can’t be explained by modules and neurons and synapses and neurotransmitters. We will soldier on without them. There are others who think that it can be. I find that being able to explain consciousness with modules, neurons, synapses, and neurotransmitters is even more wondrous and fascinating. It may not be glamorous and transcendent, but it sure is captivating.
THE UNSOLVED MYSTERY
One of the mysteries of consciousness is how a perception or information enters into consciousness from the nonconscious depths. Is there a gatekeeper that lets only some information through? What information is allowed through? What determines that? What happens after that? How do new ideas form? What processes are contributing to consciousness? Are all animals equally conscious or are there degrees of consciousness? Is our consciousness unique? The question of consciousness has been rather like the holy grail of neuroscience. If you tell me you are interested in knowing just exactly what parts of the brain are active when you are conscious of something—a flower, a thought, a song—what you are asking about is known as the neural correlates of consciousness (NCC). You are not the lone coyote on this quest. No one knows exactly what is going on, but there are plenty of suggestions. So let’s see how many of those questions have been answered and what the theories are about the rest.
Many researchers have proposed definitions and criteria for different levels of consciousness, to the point where it has gotten rather confusing.4, 5 Progressive levels of consciousness are commonly named unconsciousness, consciousness, self-awareness, and meta-self-awareness, which means you know that you are self-aware.
Antonio Damasio6 takes out his scalpel and slices consciousness down even further to only two choices: core consciousness and extended consciousness. Core consciousness is what goes on when the on-off switch is flipped on and an organism is awake and aware of one moment, now, and one place, here. It is alert and not concerned with the future or the past. This consciousness is not aware of self and is not uniquely human. It is, however, the foundation that is necessary to build increasingly complex levels of consciousness, which Damasio calls extended consciousness. Extended consciousness is what we normally think of when we think of being conscious. Extended consciousness is complex and is made up of many levels. For instance, one level of consciousness is being aware of one’s surroundings and the chocolate cake on the table. Another is being aware of them and knowing they are different from yesterday and may be different tomorrow. (The cake wasn’t there yesterday, and most likely will be gone tomorrow, so dig in now!) These aspects of consciousness have to do with content, the components of conscious experience. The highest level is knowing that one is aware of one’s surroundings and, I might add, what that cake will do to your waistline, and caring. I know for sure that dogs do not care about their waistlines. This involves the autobiographical self.
What we want to know is whether there is a systematic way that information processing reaches consciousness, and if so, what it is, how it works, and what aspects of this system may be uniquely human. To figure this out, we are going to start with some rough neuroanatomy, including what has been learned from persons with different brain lesions and from neuroimaging studies. Then we are going to look at some theories.
THE PHYSICAL BASIS OF CONSCIOUS EXPERIENCE
First, we need to know what brain areas are needed for core consciousness—the “on” switch. It begins in the brain stem. The brain stem* is the lower part of the brain, structurally continuous with the spinal cord, the first station on the way to the cortex. It is a structure that is evolutionarily old. All vertebrate animals have a brain stem, but they are not all made up of the same types of neurons. The brain stem is a complicated place. It is like all those subbasements in skyscrapers, full of pipes, vents, wires, and gauges, which are connected to the rest of the building. They keep everything running smoothly, but no one up on the thirty-fourth floor even thinks about them. If you were to disconnect some of the wiring, then the thirty-fourth floor would know something was amiss, whether it was the lights, the AC, or the telephones. If you were to disconnect all the wires, everything would shut down.
Just like the guy on the thirty-fourth floor, you have no idea what is going on in your brain stem. You are not conscious that different groups of neurons, known as nuclei, are relaying signals from your entire body related to the current state of your guts, heart, lung, balance, and musculoskeletal frame to parts of the brain higher up, with connections that are both sending and receiving information in the form of impulses. The main job of these brain-stem nuclei is the homeostatic regulation of both body and brain. They are fundamental for cardiovascular, respiratory, and intestinal control. Disconnect the brain stem, and the body dies. This is true for all mammals.
These groups of neurons have their dendrites in many pies. Some are required for consciousness, and those are connected with the intralaminar nuclei (ILN) of the thalamus. Others are required to modulateconsciousness, like a rheostat; they make up part of the arousal system. These are connected to the basal forebrain,† the hypothalamus, and directly to the cortex.7 Our party-hearty boys are not irreversibly unconscious. We can pinch them or throw cold water on them, and they will wake up. Their consciousness was being modulated by the arousal system via the connections that pass on to the basal forebrain and the hypothalamus.
Core consciousness is the first step to extended consciousness. If the wiring for core consciousness is disconnected, the pinch or the cold water will not bring anyone back to wakefulness. This is where the neurons that connect the brain stem with the intralaminar nuclei of the thalamus are the stars. There are two ILNs in the thalamus, one in the right side and one in the left. The thalamus itself is about the size of a walnut and sits astride the midline, smack dab in the center of the brain. Small, strategically placed bilateral lesions to the ILN in the thalamus turn consciousness off forever, although a lesion in one alone will not.8 If the ILNs of the thalamus don’t get their input from the connections to the brain stem, they are likewise kaput. So we have the first step on the road to consciousness: The connection of the brain stem to the thalamus must be active, and at least one of the ILNs must be up and running.
Where do the pathways from the brain stem go beyond the ILNs? Wherever they go, some must be involved with consciousness also. Now the thalamus, of which the ILNs are a part, is a well-connected dude. Neuronal connections link it to specific regions all over the cortex, and those regions send connections straight back to the thalamus. It has connection loops, which will become important a little later on in our discussion. The ILNs themselves connect to the anterior portion of the cingulate cortex. Lesions anywhere from the brain stem to the cingulate cortex can disrupt core consciousness.
It appears that the cingulate cortex is where core consciousness and extended consciousness overlap. The cingulate cortex sits on top of the corpus callosum, the great bundle of neurons that connects the right and left hemispheres. Damasio reports that patients with lesions in their cingulate cortex have disruptions in both core and extended consciousness, but oftentimes can recover core consciousness.
Well then, if the cingulate cortex is involved with extended consciousness, is it well connected too? During the performance of conscious tasks, connections from the cingulate cortex to brain areas supporting the five neural networks for memory, perception, motor action, evaluation, and attention activate. Something else is happening, too. While engaging in a wide assortment of conscious tasks that require different types of brain activity, another area of the brain also is always activated, along with the anterior cingulate cortex (ACC). That was the dorsal lateral prefrontal cortex (dlPFC). And it is no coincidence that these two areas have reciprocal connections—more loops. Moreover, in the ACC there is a particular type of long-distance spindle cell that is present only in the great apes.9 And, as you may have guessed, the dlPFC is also a hotbed of connections to the same five neural networks mentioned above.* Way back in chapter 1, we discussed the different layers of the cortex. These long-distance neurons originate mostly from the pyramidal cells of layers II and III. These layers are actually thicker in the dlPFC and inferior parietal cortex.
Extended Consciousness and Modularity
We are now getting to areas in the brain that are more specialized. If they become damaged, the result is the loss of a specific ability, not con sciousness itself. Throughout this book, there has been much talk about modules in the brain and how each has its specific contribution. The idea of a module of neurons dedicated for such specific duties such as reciprocity or cheater detection is fascinating, and the modularity of the brain becomes even more apparent when lesions in the same specific part of different brains cause the same specific deficit, such as the inability to recognize familiar faces. The odd thing is, we don’t feel that fractionated. That is one of the reasons why we find these modules so fascinating (and why the very idea of a modular brain can be difficult to believe). “My brain is doing that? Crazy!” No, you didn’t have any idea, because these modules are all working automatically, under cover, below the level of consciousness. For instance, if certain stimuli trick your visual system into constructing an illusion, consciously knowing that you have been tricked does not make the illusion disappear. That part of the visual system is not accessible to conscious control. We need to remember that all that nonconscious stuff is also contributing to and shaping what comes to the conscious surface. Another thing to keep in mind is that some stuff just cannot be processed nonconsciously. Unfortunately, your high school trig exam may have been an early reminder of this.
If consciousness requires the input of several modules, then the other problem we have to remember is connectivity. We learned in the first chapter that there are only a limited number of connections per neuron, and the more modules there are, the less they are interconnected. Even keeping this in mind, the sheer number of neurons and their connections, ah, well, boggles the mind. The human brain has approximately one hundred billion neurons, and each, on average, connects to about one thousand other neurons. A quick little conscious multiplication reveals that there are one hundred trillion synaptical connections. So how is all this input getting spliced and integrated into a coherent package? To put it anthropomorphically, how does one module know what all the other ones are doing? Or does it? How do we get order out of this chaos of connections? Even though it may not always seem so, our consciousness is rather kicked back and relaxed when you think about all the input with which the brain is being bombarded and all the processing that is going on. In fact, it is as if our consciousness is out on the golf course like the CEO of a big company while all the underlings are working. It occasionally listens to some chatter, makes a decision, and then is out sunning itself. Ah…is that why they call some types of brain processing executive functions?*
Beyond Modularity
The modular crowd recognizes that not all mental activities can be explained by modules. Sometimes you have to step out of that cubicle and communicate with other cubicles. At some point along the processing route, the input from the modules needs to be synthesized, spliced together, and packaged—or ignored, suppressed, and inhibited. Here is the big mystery. How does it happen? Some controlled processing is going on, and there must be a mechanism that supports flexible links among these processing modules. Many theoretical models of this mechanism have been proposed, including the central executive,10 the supervisory attention system,11 the anterior attention system,12, 13 the global workspace,14 and the dynamic core.15
What processes need to be brought together? There are certain components to human consciousness, which we can figure out simply by thinking about what general mental tools we are using. By doing this we are accessing our consciousness and are able to identify what we are conscious of. Let’s just pretend you are still conscious while reading this paragraph, and I haven’t flipped your arousal switch off. Or maybe your mind has begun to wander, wondering where you should go on vacation next summer or what color to paint the kitchen. Your conscious thoughts require some form of attention, either to these words or visions of the Côte d’Azur. You may be using short-term memory (working memory) to keep track of what you have read, or long-term memory to call into mind past vacations or the color of your friend’s kitchen. You also are using your visual perceptions and language ability while reading this, and most likely while you are formulating your presentation of sun-drenched afternoons sipping pastis. You may be silently talking to yourself (known as inner speech), listing the reasons why this vacation is a good idea. Not only is all that contributing to your consciousness, but so are your emotions and desires. Once all these mechanisms are running, you end up being able to reason about what I have written and fit it in with what you already know, or to figure out how to talk your spouse into renting that villa. The good thing is, you are not thinking about your income taxes or picking up your dry cleaning…uh-oh, now you are. That is an example of top-down attention.
There are two phenomena we have to explain. One is that we feel like smoothly running, coherently thinking beings who are usually in control of our thoughts. We usually don’t feel like police dispatchers with reports coming in from hundreds or thousands of different sources, deciding what is important or useful or not, or like triage nurses lining up incoming information in order of its importance, but somehow this is happening in our brains. Look around the room you are in and then close your eyes. Was it dusty? How many pencils and pens were on the table or desk? Were there any birds or flowers out the window? How about any dust on the screen? How many other books were in the room? Who wrote them? All this information is going in through your eyes, being perceived and processed and sorted unconsciously, but it is not all making it up to the level of consciousness (luckily) until you direct your attention to it. We also have to explain how we come out with a feeling of ourselves, with our own autobiography; and why, although our consciousness changes from minute to minute, our conscious sense of self does not. Somehow, information is being integrated into a nice package.
THE GATEKEEPER TO CONSCIOUSNESS: ATTENTION
Only certain information makes it through to consciousness. It is a dog-eat-dog world in our brains. Experiments have shown that in order for a stimulus to reach consciousness, it needs a minimal amount of time to be present, and it needs to have a certain degree of clarity. However, this is not quite enough. The stimulus has to have an interaction with the attentional state of the observer. This can occur in two ways, which are referred to as either top-down or bottom-up processing. Just exactly what is going on here is not known, but Stan Dehaene, Jean-Paul Changeux, a neuroscientist at the Pasteur Institute in Paris, and various collaborators suggest that the top-down mode, when you consciously direct your attention, may be a result of activity in the thalamocortical neurons, those loops that I mentioned earlier. In the bottom-up mode, they suggest, the sensory signals coming from nonconscious activity have so much strength that they can reorient top-down amplification to themselves.16 This is when your attention may be captured without conscious control. For example, you may be concentrating on a project at work, when all of a sudden you realize you are hearing the fire alarm.
You should note here an important point: Attention and consciousness are two separate animals. First off, cortical processors control the orientation of attention. Although there may be top-down voluntary control, there may also be bottom-up nonconscious signals of such strength that they can co-opt attention. We experience this all the time. You may be consciously thinking about the project that you are working on, when off go your thoughts to somewhere else, seemingly beyond your control. Second, although attention may be present, it may not be enough for a stimulus to make it to consciousness.17 You are reading that article about string theory, your eyes are focused, you are mouthing the words to yourself, and none of it is making it to your conscious brain, and maybe it never will.
SELECTIVE DISRUPTIONS OF CONSCIOUSNESS
Brain lesions in the parietal lobe that affect attention can also affect consciousness. This is shown in a dramatic way in people who have lesions, usually caused by a stroke in the right parietal lobe, that cause disruptions of attention and spatial awareness. These people often behave as if the left side of their world, including the left side of their body, does not exist. If you were to visit such a person, and entered the room on the left, he would not realize you were there. If you served him dinner, he would eat from only the right side of the plate! He would have shaved only the right side of his face, (or if a woman, would have put makeup on only the right side), would read to you only the right page of a book or newspaper, and would draw only the right side of a clock, or half of a bicycle. But what is truly odd, they don’t think there is anything wrong! They are not conscious of their problem.
This syndrome is known as hemineglect. It includes a lack of awareness for sensory events located toward the side opposite the side where the lesion is (e.g., toward the left following a right-hemisphere lesion), as well as a loss of other actions that would normally be directed toward that side.18 Some patients may neglect half their body, attempting to climb out of bed without moving their left arm or leg, even though they have no motor weakness on that side. Neglect can also be present in memory and imagination. One patient, when asked to describe the view from one end of a piazza from memory, described only the right half, but when asked to describe it from the other end looking back, described the other half with no reference to what had just been described from the other direction.19 This phenomenon indicates that our autobiographical self is derived from our conscious musings. If we are not conscious of it, it doesn’t exist.
Many patients with hemineglect do not realize that they are missing any information. This is known as anosognosia. If their lesion has also caused paralysis, they remain unaware of it. They will tell you the limp arm next to them belongs to someone else. They can be aware that they have been diagnosed with a deficit, but may refuse to believe it. One patient stated, “I knew the word ‘neglect’ was a sort of medical term for whatever was wrong, but the word bothered me because you only neglect something that is actually there, don’t you? If it’s not there, how can you neglect it? It doesn’t seem right to me that the word ‘neglect’ should be used to describe it. I think concentrating is a better word than neglect. It’s definitely concentration. If I am walking anywhere and there’s something in my way, if I’m concentrating on what I’m doing, I will see it and avoid it. The slightest distraction and I won’t see it.”20
As this patient hints, the odd thing about hemineglect is that although it can occur when there is actual loss of sensation or motor systems, it can also occur when all the sensory modalities and musculoskeletal systems are working. Neglect seems to be a loss of conscious awareness of these stimuli. Indeed, if you present a visual stimulus to both the right and left side at once, patients with left hemineglect report seeing only the right stimulus, and appear unconscious of the left stimulus. However, if you present the same left visual stimulus in isolation, so that it hits the same exact place on the retina, with no right visual stimulus at all, the left stimulus would be perceived normally. If there is no competition from the normal side, then the neglected side will be noticed.
We were the first to study this phenomenon in a controlled study, over twenty-five years ago. Bruce Volpe, Joseph LeDoux, and I asked the question, “Can information in the neglected field be used at a nonconscious level?” We presented pictures or words, one to each visual field. The only thing the patient suffering from hemineglect had to do was say if the two words or pictures were the same or different. Now remember, because they had neglect, when some sort of stimulus was presented to each visual field, they always verbally stated they conciously saw only the one stimulus, the one that was presented to their left (language) hemisphere. Nonetheless, when they were asked to judge if the words or pictures were the same or different, they responded very well. In short, somehow, somewhere in the brain, the information was combined, and a correct decision was possible, even though the patient was unable to say what the different stimulus was that had been presented to the right hemisphere. Needless to say, if they had guessed “same,” they would have concluded in a post-hoc sort of way that the stimuli had been the same.
This experiment started a small cottage industry of experiments exploring what kinds of processes could go on subconsciously. For example, word-priming studies have also shown that even when a word is presented to the neglected field and the patient denies its presence, the information is still being processed unconsciously and would be used for word identification.21
So even if the information is there at the nonconscious level, in order for it to make it to consciousness, and for the person to become aware it is there, attention has to be directed to it. Furthermore, neglect is most apparent in competitive situations, in which information on or closest to the “good” side comes to dominate information on the “bad” side.18
Another odd thing is that when a patient is asked about the presence of the limp arm, instead of saying that he doesn’t feel it, he goes so far as to say that it belongs to someone else. What’s up with that? If asked to do something that requires the use of both hands, instead of replying that he is unable to, he will reply simply that he doesn’t want to. And why don’t these patients complain about the problem? If you couldn’t see the left half of the room, wouldn’t you complain?
This is where split-brain patients are going to help out with explaining this phenomenon and also shed some light on consciousness. The largest tract of neurons in the brain is called the corpus callosum, (CC), and it connects the two hemispheres, along with a smaller tract of neurons in the front part of the brain called the anterior commissure. The corpus callosum contains about two hundred million neurons that originate in which cortical layers? You guessed it: II and III,22 the layers where most of the long-distance neurons originate. The corpus callosum has not been the focus of much attention in the past, but in light of the growing significance of the modularity and lateral specializations of the brain, this connectivity can be seen in an evolutionary light, as we touched on in chapter 1.
SPLITTING THE BRAIN
The surgical procedure to cut the corpus callosum is a last-ditch treatment effort for patients with severe intractable epilepsy for whom no other treatments have worked. Very few patients have had this surgery, and it is done even more rarely now because of improved medications and other modes of treatment. In fact, there have been only ten split-brain patients that have been well tested. William Van Wagenen, a Rochester, New York, neurosurgeon, performed the procedure for the first time in 1940, following the observation that one of his patients with severe seizures got relief after developing a tumor in his corpus callosum.23
Epileptic seizures are caused by abnormal electrical discharges that in some people spread from one hemisphere to the other. It was thought that if the connection between the two sides of the brain was cut, then the electrical impulses causing the seizures wouldn’t spread from one side of the brain to the other. The great fear was what the side effects of the surgery might be. Would it create a split personality, with two brains in one head? In fact, the treatment was a great success. Most patients’ seizure activity decreased 60 to 70 percent, and they felt just fine: no split personality, no split consciousness.24, 25 Most seemed completely unaware of any changes in their mental processes. This was great, but puzzling nonetheless. Why don’t split-brain patients have dual consciousness? Why aren’t the two halves of the brain conflicting over which half is in charge? Is one half in charge? Is consciousness and the sense of self actually located in one half of the brain?
Split-brain patients will do subtle things to compensate for their loss of brain connectivity. They may move their heads to feed visual information to both hemispheres, or talk out loud for the same purpose, or make symbolic hand movements. Only under experimental conditions, when we eliminate cross-cuing, does the disconnection between the two hemispheres become apparent. We are then able to demonstrate the different abilities of the two hemispheres.
Before we see what is separated after this surgery, we need to understand what continues to be shared. There are subcortical pathways that remain intact. Both hemispheres of the split-brain patient are still connected to a common brain stem, so both sides receive much of the same sensory and proprioceptive information automatically coding the body’s position in space. Both hemispheres can initiate eye movements, and the brain stem supports similar arousal levels, so both sides sleep and wake up at the same time.26 There also appears to be only one integrated spatial attention system, which continues to be unifocal after the brain has been split. Attention cannot be distributed to two spatially disparate locations.27 The left brain does not pay attention to the blackboard while the right brain is checking out the hot dude in the next row. Emotional stimuli presented to one hemisphere will still affect the judgment of the other hemisphere.
You may have been taught in anatomy lectures that the right hemisphere of the brain controls the left half of the body and left hemisphere controls the right half of the body. Of course, things are not quite that simple. For instance both hemispheres can guide the facial and proximal muscles, such as the upper arms and legs, but the separate hemispheres have control over the distal muscles (those farthest from the center of the body), so that, for example, the left hemisphere controls the right hand.28 While both hemispheres can generate spontaneous facial expressions, only the dominant left hemisphere can generate voluntary facial expressions.*29 Because half the optic nerve crosses from one side of the brain to the other at the optic chiasm, the parts of both eyes that attend to the right visual field are processed in the left hemisphere, and vice versa. This information does not cross over from one disconnected hemisphere to the other. If the left visual field sees something in isolation from the right, only the right side of the brain has access to that visual information. This is why these patients will move their heads to input visual information to both hemispheres.
It has also been known since the first studies of Paul Broca† that our language areas are usually located in the left hemisphere (with the exception of a few left-handed people). A split-brain patient’s left hemisphere and language center have no access to the information that is being fed to the right brain. Bearing these things in mind, we have designed ways of testing split-brain patients to better understand what is going on in the separate hemispheres. We have verified that the left hemisphere is specialized for language, speech, and intelligent behavior, while the right is specialized for such tasks as recognizing upright faces, focusing attention, and making perceptual distinctions.
Where attention is concerned, the hemispheres interact quite differently in their control of reflexive versus voluntary attention processes.30, 31, 32 There is a limited amount of overall available attention.33 The evidence suggests that reflexive (bottom-up) attention orienting happens independently in the two hemispheres, while voluntary attention orienting involves hemispheric competition, with control preferentially lateralized to the left hemisphere. The right hemisphere, however, attends to the entire visual field, whereas the left hemisphere attends only to the right field.34, 35, 36 This can explain part of the problem of our hemineglect patients. When the right inferior parietal lobe is damaged, the left parietal lobe remains intact. However, the left parietal lobe directs its visual attention only to the right side of the body. There is no brain area paying attention to what is going on in the left visual field. The question that remains is, why doesn’t this bother the patient? I’m getting there.
Breaking Up Is Not So Hard to Do
The left hemisphere is specialized for intelligent behavior. Don’t leave home without it!
After the human cerebral hemispheres have been disconnected, the verbal IQ of a patient remains intact,37, 38 and so does his problem-solving capacity. There may be some deficits in free-recall capacity and in other performance measures, but isolating essentially half of the cortex from the dominant left hemisphere causes no major change in cognitive functions. The left remains unchanged from its preoperative capacity, and the largely disconnected, same-size right hemisphere is seriously impoverished in cognitive tasks. Although the right hemisphere remains superior to the isolated left hemisphere for some perceptual* and attentional skills, and perhaps also emotions, it is poor at problem solving and many other mental activities. A brain system (the right hemisphere) with roughly the same number of neurons as one that easily cogitates (the left hemisphere) is incapable of higher-order cognition—convincing evidence that cortical cell number by itself cannot fully explain human intelligence.39
The difference between the two hemispheres in problem solving is captured in a probability-guessing experiment. We have subjects try to guess which of two events will happen next: Will it be a red light or a green light? Each event has a different probability of occurrence (e.g., a red light appears 75 percent of the time and a green 25 percent of the time), but the order of occurrence of the events is entirely random. There are two possible strategies one can use: frequency matching or maximizing. Frequency matching would involve guessing red 75 percent of the time and guessing green 25 percent of the time. The problem with that strategy is that since the order of occurrence is entirely random, it can result in a great deal of error, often being correct only 50 percent of the time, although it could result in being correct 100 percent of the time also, but it is fully dependent upon luck. The second strategy, maximizing, involves simply guessing red every time. That ensures an accuracy rate of 75 percent, since red appears 75 percent of the time. Animals such as rats and goldfish maximize. In Vegas, the house maximizes. Humans, on the other hand, match. The result is that nonhuman animals perform better than humans in this task.
The human’s use of this suboptimal strategy has been attributed to a propensity to try to find patterns in sequences of events, even when told the sequences are random. George Wolford, Michael Miller, and I tested the two hemispheres of split-brain patients to see if the different sides used the same or different strategies.40 We found that the left hemisphere used the frequency-matching strategy, whereas the right hemisphere maximized! Our interpretation was that the right hemisphere’s accuracy was higher than the left’s because the right hemisphere approaches the task in the simplest possible manner with no attempt to form complicated hypotheses about the task.
However, more recent tests have yielded even more interesting findings. They have shown that the right hemisphere uses frequency matching when presented with stimuli for which it is specialized, such as facial recognition, and the left hemisphere, which is not a specialist in this task, responds randomly.41 This suggests that one hemisphere cedes control of a task to the other if the other hemisphere specializes in that task.42 The left hemisphere, on the other hand, engages in the human tendency to find order in chaos. The left hemisphere persists in forming hypotheses about the sequence of events even in the face of evidence that no pattern exists—in playing slot machines, for instance. Why would the left hemisphere do this, even when it can be nonadaptive?
The Left Hemisphere Is a Know-It-All
Several years ago, we observed something about the left hemisphere that was very interesting: how it deals with behaviors we had elicited from the disconnected right hemisphere about which it had no information. We showed a split-brain patient two pictures: a chicken claw was shown to his right visual field, so the left hemisphere saw only that, and a snow scene was shown to the left visual field, so the right hemisphere saw only that. He was then asked to choose from an array of pictures placed in full view in front of him. From the array of pictures, the shovel was chosen with the left hand and the chicken with the right. When asked why he chose these items, his left-hemisphere speech center replied, “Oh, that’s simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.” Here the left brain, observing the left hand’s response without knowing why it has picked that item, had to explain it. It will not say, “I don’t know.” Instead it interprets that response in a context consistent with what it knows, and all it knows is: chicken claw. It knows nothing about the snow scene, but it has to explain pointing to the shovel with the left hand. It has to find reasons for the behavior. We called this left-hemisphere process the interpreter.
We also tried the same type of test with mood shifts. We showed a command to the right hemisphere to laugh. The patient began to laugh. Then we asked the patient why she was laughing. The speech center in the left hemisphere had no knowledge of why its person was laughing, but out would come an answer anyway: “You guys are so funny!” When we triggered a negative mood in the right hemisphere by a visual stimulus, the patient denied seeing anything but suddenly said that she was upset and that it was the experimenter that was upsetting her. She felt the emotional response to the stimulus, all the autonomic results, but had no idea what caused them. Ah, lack of knowledge is of no importance, the left brain will find a solution! Order must be made. The first makes-sense explanation will do—the experimenter did it! The left-brain interpreter makes sense out of all the other processes. It takes all the input that is coming in and puts it together in a story that makes sense, even though it may be completely wrong.
THE RELATIONSHIP BETWEEN THE INTERPRETER AND CONSCIOUS EXPERIENCE
So here we are, back to the main question of the chapter: How come we feel unified when we are made up of a gazillion modules? Decades of split-brain research have revealed the specialized functions of the two hemispheres, as well as providing insights into specialization within each hemisphere. Our big human brains have countless capacities. If we are merely a collection of specialized modules, how does that powerful, almost self-evident feeling of unity come about? The answer may lie in the left-hemisphere interpreter and its drive to seek explanations for why events occur.
In 1962, Stanley Schachter and Jerry Singer at Columbia University injected epinephrine into subjects participating in a research experiment.43 Epinephrine activates the sympathetic nervous system, and the result is an increased heart rate, hand tremors, and facial flushing. The subjects were then put into contact with a confederate who behaved in either a euphoric or an angry manner. The subjects who were informed about the effects of the epinephrine attributed symptoms such as a racing heart to the drug. The subjects who were not informed, however, attributed their autonomic arousal to the environment. Those who were with the euphoric confederate reported being elated and those with the angry confederate reported being angry. This finding illustrates the human tendency to generate explanations for events. When aroused, we are driven to explain why. If there is an obvious explanation, we accept it, as did the group informed about the effects of epinephrine. When there is not an obvious explanation, we generate one. The subjects recognized that they were aroused and immediately assigned some cause to it. We talked about this in the last chapter when we discussed looking over the edge of the Grand Canyon. This is a powerful mechanism; once seen, it makes one wonder how often we are victims of spurious emotional-cognitive correlations. (I am feeling good! I must really like this guy! As he is thinking, Ah, the chocolate is working!) Split-brain research has shown us that this tendency to generate explanations and hypotheses—to interpret—lies within the left hemisphere.
Although the left hemisphere seems driven to interpret events, the right hemisphere shows no such tendency. A reconsideration of hemispheric memory differences suggests why this dichotomy might be adaptive. When asked to decide whether a series of items appeared in a study set or not, the right hemisphere is able to identify correctly items that have been seen previously and to reject new items. “Yes, there was the plastic fork, the pencil, the can opener, and the orange.” The left hemisphere, however, tends to falsely recognize new items when they are similar to previously presented items, presumably because they fit into the schema it has constructed.44, 45 “Yes, the fork [but it is a silver one and not plastic], the pencil [although this one is mechanical and the other was not], the can opener, and the orange.” This finding is consistent with the hypothesis that the left-hemisphere interpreter constructs theories to assimilate perceived information into a comprehensible whole. By going beyond simply observing events to asking why they happened, a brain can cope with such events more effectively if they happen again. In doing so, however, the process of elaborating (story making) has a deleterious effect on the accuracy of perceptual recognition, as it does with verbal and visual material. Accuracy remains high in the right hemisphere, however, because it does not engage in these interpretive processes. The advantage of having such a dual system is obvious. The right hemisphere maintains an accurate record of events, leaving the left hemisphere free to elaborate and make inferences about the material presented. In an intact brain, the two systems complement each other, allowing elaborative processing without sacrificing veracity.
The probability-guessing paradigm also demonstrates why having an interpreter in one hemisphere and not the other would be adaptive. The two hemispheres approach problem-solving situations in two different ways. The right hemisphere bases its judgments on simple frequency information, whereas the left relies on the formation of elaborate hypotheses. Sometimes it is just a random coincidence. In the case of random events, the right hemisphere’s strategy is clearly advantageous, and the left hemisphere’s tendency to create nonsensical theories about random sequences is detrimental to performance. This is what happens when you build a theory on a single anecdotal situation. “I vomited all night. It must have been the food was bad at that new restaurant where I ate dinner.” This would be a good hypothesis if everyone who ate what you ate became ill, but not just one person. It may have been the flu, or your lunch. In many situations, however, there is an underlying pattern, and in these situations the left hemisphere’s drive to create order from apparent chaos would be the best strategy. Coincidences do happen, but sometimes there really is a conspiracy. In an intact brain, both of these cognitive styles are available and can be implemented, depending on the situation.
The difference in the way the two hemispheres approach the world can be seen as adaptive. It might also provide some clues about the nature of human consciousness. In the media, split-brain patients have been described as having two brains. The patients themselves, however, claim that they do not feel any different after the surgery than they did before. They do not have any sense of the dual consciousness implied by the notion of having two brains. How is it that two isolated hemispheres give rise to a single consciousness? The left-hemisphere interpreter may be the answer. The interpreter is driven to generate explanations and hypotheses regardless of circumstances. The left hemisphere of split-brain patients does not hesitate to offer explanations for behaviors that are generated by the right hemisphere. In neurologically intact individuals, the interpreter does not hesitate to generate spurious explanations for sympathetic nervous system arousal. In these ways, the left-hemisphere interpreter may generate a feeling in all of us that we are integrated and unified.
In his masterpiece, The Alexandria Quartet, Lawrence Durrell tells a story in four books, Justine, Balthazar, Mountolive, and Clea. Each of the first three books tells the story of a group of people living in Alexandria, Egypt, just before World War II, from the viewpoint of a different character. If you were to read only the first book, Justine, you would have a distorted idea of all that was going on. The second book, Balthazar, gives you more information, and the third even more. In all three, however, the reader is at the mercy of the narrators. Your interpretation of the story is dependent upon what they tell you: Your interpretation is dependent upon the supplied information. This is true for the interpretive system in the brain, also. The conclusions of an interpretive system are only as good as the information it receives.
Now, finally, we can consider our patients with hemineglect. First, let’s start with an easy case. If a person has a lesion in the optic nerve that carries information about vision to the visual cortex, the damaged nerve ceases to carry that information; the patient complains that he is blind in the relevant part of his visual field. For example, such a patient might have a huge blind spot to the left of center in his visual field. No wonder he complains. However, if another patient has a lesion not in the optic tract but in the visual cortex (the area where the visual information is processed after it is received), and it creates a blind spot of the same size in the same place, he usually does not complain at all. The reason is, the cortical lesion is in the place in his brain that represents an exact part of the visual world, the place that ordinarily asks, “What is going on to the left of visual center?” With a lesion on the optic nerve, this brain area was functioning; when it could not get any information from the nerve, it squawked—“something is wrong, I am not getting any input!” When that same brain area is itself damaged and no longer does its job, the patient’s brain no longer has an area responsible for what is going on in that part of the visual field; for that patient, that part of the visual field no longer exists, so there is no squawk at all. The patient with the central lesion does not have a complaint because the part of the brain that might complain has been incapacitated, and no other takes over.
As we move further down the line into the brain’s processing centers, we see the same pattern, but now the problem is with the interpretive function. The parietal cortex is constantly seeking information on the arm’s position in three-dimensional space, and it also monitors the arm’s existence in relation to everything else. If there is a lesion in the sensory nerves that bring information to the brain about where the arm is, what is in its hand, or whether it is in pain or feels hot or cold, the brain communicates that something is wrong: “I am not getting any input! Where’s the left hand? I can’t feel a thing!” But if the lesion is in the parietal cortex, that monitoring function is gone with no squawk raised, because the squawker is damaged. Consider our case of anosognosia and the disowned left hand. A patient with a right parietal lesion suffers damage to the area that represents the body’s left half. It is as if that part of the body has lost its representative in the brain and left no trace. There is no brain area that knows about the left half of the body and whether it is working or not. When a neurologist holds a patient’s left hand up to the patient’s face, the patient gives a reasonable response: “That’s not my hand.” The interpreter, which is intact and working, cannot get news from the parietal lobe; in fact, it does not even know that there should be news from the parietal lobe, since the flow of information has been disrupted by the lesion. For the interpreter, which is dependent upon the information it receives, the left hand simply does not exist anymore, just as seeing behind the head or wagging a tail is not something the interpreter is supposed to worry about. It is true, then, that the hand held in front of him cannot be his. In this light, the claims of the patient are more reasonable.
Reduplicative paramnesia is another odd syndrome, in which there is the delusional belief that a place has been duplicated, or exists in more than one spot at the same time, or has been moved to a different location. One such patient I had was a woman who, although she was being examined in my office at New York Hospital, claimed we were in her home in Freeport, Maine. The standard interpretation of this syndrome is that she made a duplicate copy of a place (or person) and insisted there were two.
This woman was intelligent; before the interview she was biding her time reading the New York Times. I started with the “So, where are you?” question. “I am in Freeport, Maine. I know you don’t believe it. Dr. Posner told me this morning when he came to see me that I was in Memorial Sloan-Kettering Hospital and that when the residents come on rounds to say that to them. Well, that is fine, but I know I am in my house on Main Street in Freeport, Maine!”
I asked, “Well, if you are in Freeport and in your house, how come there are elevators outside the door here?” The grand lady peered at me and calmly responded, “Doctor, do you know how much it cost me to have those put in?”
This patient’s interpreter tried to make sense of what she knew and felt and did. Because of her lesion, the part of the brain that represents locality was overactive and sending out an erroneous message about her location. The interpreter is only as good as the information it receives, and in this instance it was getting a wacky piece of information. Yet the interpreter still has to field questions and make sense of other incoming information—information that to the interpreter is self-evident. The result? A lot of imaginative stories.
In Capgras’ syndrome, patients will recognize a familiar person but will insist that the person is an imposter and has been replaced by an identical double. For instance, a woman will say Jack (who really is her husband) looks like her husband, but he really isn’t her husband, he’s a double, or an alien. In this syndrome, it appears that the emotional feelings for the familiar person are disconnected from the representation of that person.46 The patient feels no emotion when they see the familiar person. The interpreter has to explain this phenomenon. It is receiving the information from the face identification module: “That’s Jack.” However, it is not receiving any emotional information. Therefore in order to explain the situation, the interpreter comes up with a solution: “It must not really be Jack, because if it really were Jack I’d feel some emotion, so he is an imposter!”
I JUST GOTTA BE ME! SELF-AWARENESS
The interpreter also has other duties. This system that started out making sense of all the information bombarding the brain—interpreting our cognitive and emotional responses to what we encounter in our environment, asking how one thing relates to another, making hypotheses, bringing order out of chaos—also creates a running narrative of our actions, emotions, thoughts, and dreams. The interpreter is the glue that keeps our story unified and creates our sense of being a coherent, rational agent. Insertion of an interpreter into an otherwise functioning brain creates many by-products. A device that begins by asking how one thing relates to another, a device that asks about an infinite number of things, in fact, and that can get productive answers to its questions, cannot help but give birth to the concept of self. Surely one big question the device would ask is, “Who is solving all these problems? Hmm…Let’s call it me”—and away it goes!*
“My sense of self is a by-product?”
Yes, sorry. Now at this point we could get all philosophical or Freudian about what is self or I, but we aren’t going there. We are going to cognitive psychology instead.
It is generally agreed that self-cognition is constructed from several distinct processes, and several different proposals have been made as to what processes make up self-cognition. John Kihlstrom and my colleague Stan Klein47 at the University of California, Santa Barbara, emphasize that the self is a knowledge structure, not a mystical entity. They have suggested that there are four categories of self-knowledge that are stored and cataloged in different formats in the brain.
1. The conceptual self: a fuzzy set of context-specific selves united by a theory of how we got to be the person that we are. “I am a generous (or stingy), happy (or taciturn), and swell (or jerky) guy because my parents (or church or society or Bacchus) taught me (or made me) to be that way.” According to Pascal Boyer and colleagues48 this would include the domain of social systems: The self-concept includes notions of social identity or moral status and also includes the capacities for theory of mind and empathy.
2. The self as a narrative, which we have constructed, rehearsed to ourselves, and told to others about the past, present, and future. “I was born on a ranch, grew up breaking horses, and knew rodeo was my life.”
3. The self viewed as an image, with details about face, body, and gestures. “I am slender, graceful, and quite striking. You gotta see me tango!”
4. An associative network with information about personality traits, memories, and experiences, stored separately in episodic and semantic memory. “I am confident and outgoing and always have a great tan. I was born in Tahiti, moved to Hawaii, had a great time there, and won the state surfing championships on a totally gnarly surf day. Chicks dig me.”
This is sounding suspiciously familiar. I submit that it is the left-brain interpreter that is coming up with the theory, the narrative, and the self-image, taking the information from various inputs, from the “neuronal workspace,” and from the knowledge structures, and gluing it together, thus creating the self, the autobiography, out of the chaos of input.
Do these knowledge structures about self differ from other knowledge structures? Some neuropsychologists think not much. James Gilligan and Martha Farah at the University of Pennsylvania think that most structures are probably not distinct from processes involving persons in general.49 This actually makes a lot of sense in terms of brain economy. I propose that the left-brain interpreter is uniquely human. It can take information from a wide variety of sources, the same sources that are available to other animals, but it integrates that information in a unique way to create our self-conscious self. There has been a phase shift. The degree to which humans are self-aware is unique.
However, there may be some specialized knowledge structures that we will consider that give our interpreter an edge. First we are going to learn a bit about memory, and then we are going back to patients with lesions that affect the sense of self, to see if we can learn anything more. Remember that the interpreter can use only information that it has available.
Consider the trip to the Côte d’Azur. In proposing such a trip, you are using information that you know about yourself that indicates that you will enjoy the trip. Where is this information coming from? How about your travel partner? Is the same information available about another person, and is it stored as memory in the same place? One fascinating aspect of memory that was noticed several years ago was that if you asked a person if a certain word was self-descriptive, that word would later be remembered better than if you asked about the word in a more general sense. For instance a person would remember the word kind better if he had been asked, “Are you kind?” than if he had been asked, “What does kind mean?”50 This led researchers to believe that self-knowledge might be stored in a different manner than other information.
Memory stores two basic types of information: procedural and declarative.51 Procedural memory allows one to retain perceptual, motor, and cognitive skills and express them nonconsciously, such as driving a car, riding a bicycle, tying a shoelace, braiding one’s hair, and, eventually, playing the piano. Declarative memory is made up of facts and beliefs about the world, such as, the desert is hot in the summer, and orange blossoms are fragrant. Neuroscientist Endel Tulving, professor emeritus at the University of Toronto, proposes that there are two types of declarative memory: semantic and episodic.51, 52, 53
Semantic memory is generic: “Just the facts ma’am, just the facts,” not necessarily associated with the source or where or when they were learned. Cairo is the capital of Egypt, 12 squared is 144, and most wine is made from grapes. Semantic memory makes no subjective reference to the self, although it can have facts about the self: “I have green eyes. I was born in Timbuctoo.” Semantic memory provides knowledge from the point of view of an observer of the world rather than that of a participant. Episodic memory retains events that were experienced by the self at a particular place and time. “I had a great time at the party last night, and the food was delicious!”
Tulving is continually sculpting the definition of episodic memory as more is known about it. Because he considers episodic memory uniquely human, and since it will be important in our discussion of animal consciousness later, I will quote his most recent sculpting.
Episodic memory is a recently evolved, late developing, and early deteriorating brain/mind (neurocognitive) memory system. It is oriented to the past, more vulnerable than other memory systems to neuronal dysfunction, and probably unique to humans. It makes possible mental time travel through subjective time—past, present, and future. This mental time travel allows one, as an “owner” of episodic memory (“self”), through the medium of autonoetic awareness,* to remember one’s own previous “thought-about” experiences, as well as to “think about” one’s own possible future experiences. The operations of episodic memory require, but go beyond the semantic memory system. Retrieving information from episodic memory (“remembering”) requires the establishment and maintenance of a special mental set, dubbed episodic “retrieval mode.” The neural components of episodic memory comprise a widely distributed network of cortical and subcortical brain regions that overlap with and extend beyond the networks subserving other memory systems. The essence of episodic memory lies in the conjunction of three concepts—self, autonoetic awareness, and subjective time.54
By definition, episodic memory always includes the self as the agent or recipient of some action. When a person—let’s call her Sarah—remembers an event, she reexperiences it with the awareness that it happened to her: “I remember seeing the Stones last year. They were great!” The major distinction between episodic and semantic memory is not the type of information they encode, but the subjective experience that accompanies the operations of the systems at encoding and retrieval. Sarah could say, “I saw the Stones last year,” as a fact, even if she was too drunk to actually remember having done so. Episodic memory is rooted in autonoetic awareness and in the belief that the self having the experience now is the same self that had it originally. Semantic memory requires only noetic awareness, which is experienced when one thinks objectively about something that one knows. Tulving emphasizes that it is “possible to be noetically aware of one’s self, including body position in space, traits, and characteristics, and even autobiographical facts that are not accompanied by a feeling of re-experiencing or reliving the past.”
It is looking as though semantic memory appears earlier in development than episodic memory. Although very young children appear to be able to remember facts and can think about things that are not physically present (that is, they have semantic memory), it is difficult to determine whether they can consciously recollect the past in a way that engages a developed episodic system. Babies who are two years old have been able to demonstrate recall of things that they had witnessed at age thirteen months.55 However, several pieces of evidence support the idea that it isn’t until children are at least eighteen months old that they actually include themselves as part of the memory, although this ability tends to be more reliably present in three- to four-year-olds.56, 57 In fact, it appears that children less than four years old have no knowledge of time scales,58, 59 which is why it is never a good idea to tell them that you will be going to Disneyland in two weeks. This later-developing episodic memory explains why there is scant autobiographical memory from our very early years.
Evolutionary psychology theory, however, is not going to be happy with only episodic memory doing all the autobiographical work. It would take way too long when you need “quick and dirty” answers. If our ancestor was presented with the question of whether to chase a prey or not, he needed a fast answer about his capabilities. He couldn’t wait around while he remembered every gazelle and warthog that he had ever run after and whether his speed and endurance matched theirs, and calculate the probabilities; he needed precomputed and stored answers: “I am fast, strong, and have endurance. Go for it!” or “I am slow, wimpy, and tire easily, and besides that, warthogs are gross. I’ll just tell Cronos where it is.”
Well, guess what? The semantic system, that “Just the facts, ma’am” system, appears to have a subsystem for personality trait summaries. Stan Klein and Judith Loftus did some tests to tease out whether personality trait summaries were stored separately from episodic memory. Subjects were given pairs of tasks, the first serving as a prime for the second. The first task varied among answering if a trait was self-descriptive (“Are you generous?”), doing a filler task (“Define the word table”), or a control task (which was either looking at a blank screen or defining a trait word: “What does selfish mean?”). Next, if the first task had been answering whether a trait was self-descriptive, the second task was to remember an episode in which the subject had displayed that trait. The experimenters measured the amount of time it took to come up with the remembered episode. If the subjects had seen only a blank screen, they were presented with a new trait and asked to come up with an episode in which they had displayed that trait. The researchers reasoned that if subjects had used episodic memory to come up with an answer about whether a trait was self-descriptive (yes, I’m generous), then they should be faster at describing an episode when they displayed that trait, because they would already have thought of it to answer the first question. However, this isn’t what happened. It took subjects just as long to remember an episode of a trait that they had already been asked about as they did to remember an episode of a different trait of which no previous mention had been made. The experimenters concluded that people can answer questions about their personality traits by accessing trait summaries without invoking memories of specific episodes.60
Other research Klein and Loftus have done has shown that episodic memory is called in only when there is no trait summary available—for instance, when experience is extremely limited in regard to a specific trait. This also holds true when making judgments of other people. Episodic memory is called upon only when no trait summary exists.61 One patient with total amnesia who could not remember a single thing he had done or experienced in his life has been extensively studied. Not only does he have no episodic memory, but his semantic memory has also been partially lost. Although he could not accurately describe the personality of his daughter, he could accurately describe his own personality. He knew some facts about his life, but was missing others. He knew some well-known facts about history, but not others. This patient’s pattern of deficits strongly suggests that there is specific memory architecture for storage and retrieval of self personality traits.
The general trend from studies that have been done on self-referential traits points to left-hemisphere involvement.62 How about the autobiographical episodic memories? Can they be located? The answer to this question has been elusive; some evidence points to one side, some to the other. The picture that is emerging is that aspects of self-knowledge are distributed throughout the cortex, a little here, a little there. There is some evidence that the frontal regions of the left hemisphere play a pivotal role in setting the goal for retrieval and reconstruction of autobiographical knowledge.63, 64, 65
Do split-brain patients help us out at all with locating where self processing is located? Severing the corpus callosum in humans has raised a fundamental question about the nature of the self: Does each disconnected half brain have its own sense of self? Could it be that each hemisphere has its own point of view, its own self-referential system that is truly separate and different from that of the other hemisphere?66
Early observations of split-brain patients indicated that this could be the case.67 There were moments when one hemisphere seemed to be belligerent while the other was calm. There were times when the left hand (controlled by the right hemisphere) behaved playfully with an object that was held out of view while the left hemisphere seemed perplexed about why. However, of the dozens of instances recorded over the years, none allowed for a clear-cut claim that each hemisphere has a full sense of self. Although it has been difficult to study the self per se, there have been intriguing observations about perceptual and cognitive processing relating to the self.
Research has revealed much about the processes and brain structures that support the recognition of familiar others (for example, friends, family members, and movie stars). Both functional imaging and patient studies show that face recognition is typically reliant on structures in the right cerebral hemisphere. For example, we have shown that split-brain patients perform significantly better on tests of face recognition when familiar faces are presented to the right hemisphere rather than the left hemisphere.68 Similarly, damage to specific cortical areas in the right hemisphere impairs the ability to recognize others.69, 70, 71, 72, 73
But is the right hemisphere similarly specialized for self-recognition? Although some support has been garnered for this idea,74, 75, 76 the available evidence is inconclusive. Neuroimaging studies have revealed that highly self-relevant material (for example, autobiographical memories) activates a range of cortical networks in the left hemisphere that could, potentially, support self-recognition and a host of related cognitive functions.77, 78, 79Therefore, whereas the recognition of familiar others relies primarily on structures in the right hemisphere, self-recognition might be supported by additional left-lateralized cognitive processes. To investigate this possibility, David Turk and colleagues assessed face recognition of self versus a familiar other in a split-brain patient.80
Patient J.W. viewed a series of facial photographs that ranged from 0 percent to 100 percent self-images. A photograph of me (M.G.), a longtime associate of J.W. (that is, a highly familiar other), was used to represent 0 percent self, and a photograph of J.W. was used to represent 100 percent self. Nine additional images were generated using computer-morphing software, each image representing a 10 percent incremental shift from M.G. to J.W. In one condition (self-recognition), J.W. was asked to indicate whether the presented image was he; in the other condition (familiar-other recognition), he was asked to indicate whether the image was M.G. The only difference across the two conditions was the judgment that was required (Is it me? versus Is it Mike?).
The results revealed a double dissociation in J.W.’s face-recognition performance. His left hemisphere showed a bias toward recognizing morphed faces as self, whereas his right hemisphere showed the opposite pattern; that is, biased recognition in favor of a familiar other. In short, the left hemisphere is quick to detect a partial self-image, even one that is only slightly reminiscent of the self, whereas the right brain needs an essentially full and complete picture of the self before it recognizes the image as such. In the left hemisphere, there was, essentially, a linear relationship between the amount of self in the image and the probability of detecting self. The right hemisphere, on the other hand, did not recognize the image as self until the image contained more than 80 percent self. The finding that the left hemisphere requires less self in the image for self-recognition might reflect a key role of the left hemisphere in the retrieval of self-knowledge, or might depend on the left-brain interpreter taking whatever information is available and making a judgment call on the basis of that information. This also goes along with the right brain’s being more accurate and maximizing information, not forming a hypothesis—“Wait a minute, that is not me. That nose is not quite right,” while the left brain will frequency-match and hypothesize, “Yep that’s me!”
Overall, the data indicate that a sense of self arises out of distributed networks in both hemispheres.80, 81 It is likely that both hemispheres have processing specializations that contribute to a sense of self, and that sense of self is constructed by the left-hemisphere interpreter on the basis of the input from these distributed networks.
ANIMALS AND CONSCIOUSNESS: TO WHAT DEGREE?
This is the question that intrigues many animal researchers. The answer has been elusive. If only they could talk, they would be so much easier to study. To paraphrase Steve Martin,* “Boy, those animals! They don’t have a different word for anything!” As I mentioned earlier, there are many levels of consciousness, defined differently by different researchers. It is well accepted that mammals are conscious to the here and now, but the debate begins with the degree of extended consciousness that they possess. The problem is, how can one design an experiment that could demonstrate degrees of consciousness in a nonverbal animal? Come up with the answer to that problem and you have yourself a big fat PhD dissertation.
In order to determine degrees of extended consciousness an animal possesses, one needs to know what is considered to be extended consciousness. The basic step that is made into extended consciousness is becoming self-aware to some degree. Self-awareness means being the object of one’s own attention. Various scientists describe this as ranging from merely being aware of the products of self-perception or environmental stimuli (“I hear a noise,” “I feel a thorn”) to the ability of conceptualizing information about the self, which needs to be determined abstractly (“I am hip.”)82 This has led animal researchers to concentrate in two areas: animal self-awareness and animal metacognition (thinking about thinking).
Animal Self-Awareness
In discussing animal self-awareness, Marc Hauser makes the point that when it would pay, in evolutionary terms, to treat some members of your own species differently from others is when the discrimination leads to fitness payoffs. Thus it may pay to be able to recognize the opposite sex, or the age of another individual (if they were sexually mature…no use wasting time on courting an immature individual), or your own mother, or kin versus non-kin, or other members of your own pack or hive. He tells us, “All social, sexually reproducing organisms seem to be equipped with neural machinery for discriminating males from females, juveniles from adults, and relatives from nonrelatives.”83
Many different systems have evolved to help identify kin from non-kin. One system that many birds have is imprinting. The first individual they see is Ma. This usually works, but glitches in this system have been the basis of many cartoons. Sweat bees and paper wasps recognize their colony by odor, ground squirrels also use odor for recognition,84 and Mexican free-tail bats recognize their own pup out of thousands through vocal and olfactory communication. These recognition systems use some sensory perception to clue recognition, a match to a specified neural template, but they do not require any self-awareness, any “knowing of self” to work.
Trying to design a test to demonstrate self-awareness in animals has proven difficult. In the past it has been approached from two angles. One is mirror self-recognition and the other is through imitation. Gordon Gallup approached the problem by developing a mirror test, in which he anesthetized chimpanzees, put a red mark on one ear and eyebrow, and then, after they had recovered from the anesthesia, presented them with a full-length mirror. Prior to exposure to the mirror, the chimps didn’t touch the red marks, but once the mirror was presented, they did. After being left with the mirror, a while later they began to look at visibly inaccessible parts of their bodies.85 Not all chimps exhibit mirror self-recognition (MSR), however.86 Later experiments have shown that MSR develops in some, but not all, chimps around puberty, but is present to a lesser degree in older chimps,87 and in fact may deteriorate over time.88 Orangutans also show MSR, but only a rare gorilla possesses it.89, 90 Two dolphins91 (with a few questions still to be addressed concerning differences in testing procedures92) and one out of the five Asian elephants that have been tested in two different studies have also passed the mark test.93, 94 That’s it, folks.
No other animal species has yet been found that exhibits MSR. This is why your dog isn’t all that interested when you try to get him to look in the mirror. Children have MSR and pass the mark test by age two.95 Gallup has suggested that mirror self-recognition implies the presence of a self-concept and self-awareness.96 This sounds like a reasonable test until Robert Mitchell, a psychologist at Eastern Kentucky University, chimes in by asking, What degree of self-awareness is demonstrated by recognizing oneself in the mirror? Mitchell points out that MSR requires only an awareness of the body, rather than any abstract concept of self.97 There is no need to invoke anything more than matching sensation to visual perception; attitudes, values, intentions, emotion, and episodic memory are not required to recognize one’s body in the mirror. A chimp looks down and sees his arm and wills it to move. It moves. He sees it move in the mirror. No grand concept of self is needed. Mitchell divides the self into three levels:
1. The implicit self, a point of view that experiences, acts, and in the case of mammals and birds, has emotions and feelings. A hamster is hungry, and can experience eating and can like eating, but it probably doesn’t know that it likes to eat.
2. The self built upon kinesthetic visual matching, which leads to MSR, the first step to imitation, pretense, planning, self-conscious emotion, and imaginative experience.
3. The self built on symbols, language, and artifacts, which provides support for shared cultural beliefs, social norms, inner speech, dissociation, and evaluation by others, as well as self-evaluation.98
Another problem with the MSR test is that some patients with prosopagnosia (inability to recognize faces) cannot recognize themselves in a mirror. They think they are seeing someone else. However, they do have a sense of self, which is why the problem is so distressing to them. The absence of MSR, then, doesn’t necessarily mean the absence of self-awareness. So although the MSR test can indicate a degree of self-awareness, it is of limited value in evaluating just how self-aware an animal is. It does not answer the question of whether an animal is aware only of its visible self or if it is aware of unobservable features. Povinelli and Cant have suggested that a sense of physical self-awareness in nonhuman primates may have evolved in large arboreal primates to meet the challenges of crossing between gaps in trees, where their weight was an issue in selecting their route.99 Knowing that they had a body and that only certain structures could support it provided a survival advantage.
If one can imitate another’s actions, then one is capable of distinguishing between one’s own actions and the other’s. The ability to imitate is used as evidence for self-recognition in developmental studies of children. We have seen in chapter 5 that there is sparse evidence for imitation in the animal world. Josep Call has summarized the research, concluding that most of the evidence in primates points to the ability to reproduce the result of an action, not imitate the action itself.100
Tulving’s suggestion that episodic memory—which includes an awareness of self in its definition and the ability to project oneself into the past or future—is uniquely human has also been a field of focus to identify self-awareness. If an animal can demonstrate its capacity for episodic memory, then it must have a concept of self. Tulving outlines the challenges and pitfalls of identifying episodic memory in animals. Much research on animal memory has been concerned with perceptual memory, which doesn’t require declarative memory. Even when some tests require more than perceptual memory, they can be successfully performed using declarative semantic memory without episodic memory.
Many previous studies have assumed that animals have episodic memory when they demonstrated some behaviors. These studies, however, did not separate memory for facts, which would be semantic memory, from memory for events. Episodic memory tests require the subject to answer what, where, when (the when has been lacking in most tests), and then one final question that is the most difficult to study. Is the animal remembering the experience with an attached emotional component, or does it merely know that it happened? (This is the difference between knowing when you born versus remembering the experience of your birth, or knowing that one eats every day versus remembering the experience of a particular meal.) The problem has been figuring out how to approach that experiential aspect. In humans, we can just ask, although even this does not always give accurate information, because we have the know-it-all interpreter providing the answers. Animal studies have had to focus on behavior criteria. It has taken years to understand that much of what we do is not under conscious control, even though we thought that it was, so attributing conscious action to animals is also going to be tempting but needs to be rigorously evaluated.
Povinelli and his colleagues did an interesting study with children that revealed a developmental difference in semantic and episodic memory.101 First he unobtrusively put stickers on the foreheads of two-, three-, and four-year-olds while they were playing a game. Three minutes later, he showed them either a video of this action or a Polaroid picture of it to find out whether what a child learned about a past experience could be assimilated into the present. About 75 percent of the four-year-olds had immediately reached up and pulled the sticker off, while none of the two-year-olds and only 25 percent of the three-year-olds had done so. However, when he handed the two- and three-year-olds a mirror and they glimpsed themselves, they all immediately pulled off the stickers. The researchers suggested that the difference in reaction to live versus delayed feedback in the different age groups indicated a developmental lag between the development of a self-concept and a self-concept that includes temporal continuity. Specifically, children may not assume that their currently experienced state is determined by previous states. The two- to three-year-olds were not yet able to project themselves into the past, not yet able to time-travel. This is further indication that possessing MSR is not evidence for the possession of episodic memory and full self-awareness, and that semantic and episodic memory develop separately.
Thomas Suddendorf, a psychologist at the University of Queensland, Australia, and Michael Corballis, from the University of Auckland, New Zealand, make the interesting point that in order to have episodic memory and to time-travel, many cognitive abilities are involved. It is not just a single module doing its thing. Thus in order to establish if episodic memory is present in other species, they need to possess all the cognitive abilities required. What are these? Beyond some level of self-awareness, they must have an imagination able to reconstruct the order of events, must be able to metarepresent their knowledge (to be able to think about thinking), and must be able to dissociate from their current mental state (I am not hungry now, but I may be in the future). Episodic memory also requires that an animal understand the perception-knowledge contingency, that is, that seeing is knowing: I know that because Susan has her eyes covered, she cannot see me; or I know that because Ann is not in the room, she did not see Sally move the ball to a new place. It also requires the ability to attribute past mental states to one’s earlier self: I used to think the candy was in the blue box, but now I know that it is in the red one. These systems aren’t up and running in children until age four. Included in these cognitive abilities is a concept derived from the Bischof-Kohler hypothesis, which states, “Animals other than humans cannot anticipate future needs or drive states and are therefore bound to a present that is defined by their current motivational state.”102 That means that if an animal is not hungry now, it is unable to plan for actions in the near future that involve eating; it cannot uncouple or dissociate from its current motivation (to lie down, perhaps) to plan for something that would be the result of a different motivational state.
The idea that “animals may be stuck in time,” as suggested by a comprehensive review of animal memory studies done by William Roberts,103 a psychologist at the University of Western Ontario, seems a little farfetched when you think about how your dog “knows” it is 7:00 P.M. and time for his walk, or waits at the door for you to get home from work every day at 5:30. Or how about all those dang birds that have the intelligence to head south for the winter while you are crazy enough to stay in Buffalo, or bears eating their fill all summer and holing up for the winter? They seem to understand time and are planning ahead. These abilities turn out to be regulated by internal cues that have to do with circadian rhythms rather than a concept of time. A bear that hibernates for the first time cannot be planning ahead for the long cold winter: It doesn’t even know that there are long cold winters.
The Search for Episodic Memory in Animals
Some of the most tantalizing sets of animal studies looking for episodic memory have been done by Nicola Clayton and Anthony Dickinson, professors at the University of Cambridge, studying scrub jays.104, 105, 106, 107, 108 What was different about their studies was that they designed them to determine if the jays were answering the what, where, and when questions about multiple episodes that were unique in time and flexibly recalled. The jays more recently are even answering the who question. Thus they are using multiple components of an event, not just a single bit of information.
You may have been inadvertently using a misguided epithet when you referred to the annoying person on the phone or in traffic as a birdbrain. While most of us have been going about our daily lives, working, enjoying our vacations, and worrying about our taxes, there has been a revolution going on in the study of bird brains. I am not kidding! There has been a major change in the understanding of bird-brain anatomy and their neural connections, which has led to new ideas about the structure and function of parts of the avian brain.109 While birds lack the neocortical structure of mammals, they have many brain structures that serve the same purpose as mammalian brain structures, and have similar thalamic-cortical loop connections.110 This has led to the realization that some species of birds have a lot more going on upstairs than had previously been thought. The presence of loop connections similar to the loop connections proposed to allow extended consciousness in humans leads to the hypothesis that they are performing the same operation in birds and providing them with some level of extended consciousness. This actually should come as no surprise to anyone who has spent much time watching ravens, crows, jays, or some species of parrots.
So, back to the scrub jays: Clayton, a former colleague of mine when we were both at the University of California, Davis, found that Florida scrub jays (Aphelocoma coerulescens) will cache different types of food in different places, at different times, and will selectively retrieve food that degrades, and eat that before retrieving and eating food that stores well. Her birds fulfill the when, what, and where questions, and are flexible. What is still not answered is if it is semantic knowledge or experiential. All the jay really is demonstrating is that it can update its knowledge, as psychologist Bennett Schwartz maintains; it is like the memory of where one’s keys are. Clayton calls it episode-like memory because of this problem.111
Another tantalizing finding is that jays adjust their caching strategies to minimize potential stealing by other birds. If an individual jay (let’s call him Buzz) had stolen food from another’s cache in the past, and if while Buzz was caching his food he was observed by another jay, then after that other bird was removed, Buzz would recache his food in private. Not only that, Buzz also keeps track of who is observing him cache. If it is a dominant bird, he is more likely to rehide his food in private than if it is his mate or a subordinate bird. He is also less likely to recache his food if a new jay appears who had not watched him hide food previously.112 However, if Buzz had never stolen food from another jay in the past, then he would not recache his food even though his caching had been observed. These results indicate that recaching depended on previous experience as a thief.113 Walking on the wild side, Clayton and her coworkers suggest that maybe these scrub jays are showing evidence of knowing what another jay knows: theory of mind.
You may recall from chapter 2 the studies that revealed planning behavior in orangutans and bonobos, done by Mulcahy and Call.114 These are the best evidence so far that imaginary time travel is not unique to humans. These were the studies that demonstrated future planning of tool use when the subject carried a tool from one room to another for use up to fourteen hours later. These authors concluded:
Because traditional learning mechanisms or certain biological predispositions appear insufficient to explain our current results, we propose that they represent a genuine case of future planning. Subjects executed a response (tool transport) that had not been reinforced during training, in the absence of the apparatus or the reward, that produced no consequences or reduced any present needs but was crucial to meet future ones. The presence of future planning in both bonobos and orangutans suggests that its precursors may have evolved before 14 Ma* in the great apes. Together with recent evidence from scrub jays our results suggest that future planning is not a uniquely human ability.
Suddendorf agrees that these findings are very suggestive, but points out that the researchers did not measure or control subjects’ motivational states. He thinks, “Although the data suggest anticipation of the future need for a tool, they do not necessarily imply anticipation of a future state of mind.”115 It seems that the quest for nonhuman episodic memory is still afoot, and designing tests that can demonstrate it is the current stumbling block, although they are slowly being improved upon.
Do Animals Think About What They Know?
While most research on animals has been concentrating on the theory-of-mind question and what an animal knows about another’s knowledge, little has been done on what an animal knows about its own knowledge. A newer approach in looking for self-reflective consciousness has been to look for metacognition, or thinking about thinking, which is awareness of one’s own mental operations. Do animals think about what they know? This is another difficult question to study.
One approach has been through the testing of uncertainty. Humans know when they don’t know something, or when they are unsure of something. J. David Smith, a psychologist at the State University of New York at Buffalo, thought that designing a test that included uncertainty might demonstrate metacognition in animals. He designed a visual density test in which rhesus monkeys and humans used a joystick to move a cursor to one of three objects on a computer screen.116 They were to judge if a box was densely lit (exactly 2,950 pixels) or sparsely lit if it had fewer. They could pick the “dense” response, the “sparse” response, or the “uncertain” response, which was represented by a star on the screen. If they picked the star, they went automatically to a new guaranteed-win trial. The difficulty of making the discrimination gradually increased, until most faltered at about the 2,600-pixel level. Interestingly, the monkeys’ and the humans’ responses were much the same. After the test, the humans verbally reported that when they had guessed that the screen was either sparse or dense, their answers were dependent on the visual stimulus; however when they chose the uncertain response, it was because they had personal feelings of uncertainty and doubt: “I was uncertain,” “I didn’t know,” or “I couldn’t tell.” Smith concluded that the “uncertain” response in humans might reveal not only metacognitive monitoring but also a reflexive awareness of the self as cognitive monitor.
A similar study has been done with a male bottlenose dolphin using an auditory discrimination test. The dolphin had to press a high paddle for the high-pitched tone (2100 Hz), a low paddle for any other tone, and a third paddle if he was uncertain. This paddle was picked when the tone approached 2085 Hz or greater. The dolphin, when responding with certainty, also swam quickly to the paddle; however, when he was not, he swam more slowly and wavered between the paddles.117 The demonstration that animals had an uncertainty response and used it in situations similar to those when humans demonstrated uncertainty was interpreted to mean that monkeys and dolphins have metacognition.
Reactions to this suggestion have been varied, with some agreement and some skepticism.118 The problem is in the original assumption that the humans were thinking about thinking when they made their uncertain response. I don’t think metacognition came into the picture until they were asked about their response. That is when the left-hemisphere interpreter revved up to explain their response. The choice was powered by emotional responses to the stimuli, the old approach-don’t approach response. The problem comes from the assumption that humans were using higher cognition when they may not have been. Philosopher Derek Browne, from the University of Canterbury, Christchurch, New Zealand, has a similar take in discussing the results of the dolphin study. He suggests that it isn’t until the postexperimental probe (or question) is applied that human subjects apply psychological concepts to their own earlier performances.119
The latest tests have been done with rats by Allison Foote and Jonathon Crystal at the University of Georgia. First their rats heard either a short sound or a long one. Next, for a reward, the rats had to pick whether the recent noise had been short or long. This was easy unless they were given sounds that were intermediate in length. If the rat was correct, it got a big food reward, and if it was wrong, zilch. However, before it was given the choice, the rat could opt out of the test and get a small food reward. Sometimes, however, it was not allowed to opt out but was forced to make a choice. Two interesting things happened. The more difficult it was to distinguish the sounds, the more frequently the rats opted out of the test if they could. And second, as you would expect, test accuracy declined as the difficulty of the time-discrimination task increased, but this decline in accuracy was greater when rats were forced to do the test. The findings suggest that rats could assess whether they were going to pass a test on a trial-by-trial basis.120 They knew what they knew about the length of the sound.
Josep Call has approached metacognition from a different angle. He has provided his subjects with incomplete information to solve a problem, in order to find out whether they would seek additional information: Would they know that they did not know enough to solve a problem? He tested orangutans, gorillas, chimps, bonobos—and children two and one-half years old.121, 122 He had two opaque tubes. He put a treat in one, either while the subject could see him do it or while he was hidden behind a screen. Then he let the subject pick the tube they wanted, either right away or with a time delay. The question was, when they didn’t have enough information as to which tube had the treat inside, would they seek more information before choosing a tube? They did! In fact, in many of the trials, after the apes looked in one tube and saw that it was empty, they chose the second tube without checking it out first. They inferred that the other tube had the treat. They were better at this than the children. Preventing the apes from immediately choosing increased the looking behavior and obviously their success. However, this did not change the behavior of the children. Call suggested that it “is likely that apes were more successful in the delayed situation because they did not have to inhibit the powerful responses elicited by the prospect of getting the reward.”122 As we have learned before, inhibition is not high on the list of chimpanzee behavioral traits.
Call is very cautious about his conclusions as to what this study reveals about the cognition of great apes and whether metacognition is involved. The debate is whether they are using a fixed hardwired rule, such as “Search until you find food,” or perhaps a fixed rule learned from a specific experience, like “Bend down in the presence of a barrier,” or whether they are using a flexible rule based on knowledge accumulation created through multiple experiences, none of which were the same as the one that is now being presented, such as “When my visual access is blocked, then do something appropriate to gain visual access.” Call is inclined toward the latter explanation in his current pursuit of this question.
Can anatomy help us at all? Maybe. If we knew exactly what the neural correlates of human consciousness were, which we don’t, then we could see if their equivalent exists in other species. It appears that long-range connection loops are necessary. As I said before, these have been identified in bird brains, and also in other primates. Although much more work in comparative anatomy still needs to be done, we have a problem when we compare anatomy. It is not the same thing as comparing function. There may be more than one way to skin a cat—that is, there may be neural solutions or routes to consciousness other than those in the human brain, which could result in different types of consciousness.
So, currently we are left with Antonio Damasio’s conclusions. Some animals have some degrees of extended consciousness, but what animals possess it and to what extent is still unknown. There appears to be some degree of body self-awareness in a very limited number of species, but even as new ways for testing such abilities are designed, the many brains that evaluate the tests continue to poke holes in their validity and also their interpretation. Current evidence suggests that animals do not have episodic memory and do not time-travel, but we are going to have to keep our eyes on Nicola Clayton and her scrub jays. The latest studies looking for evidence of animal metacognition in rats are tantalizing but still need refining before definite conclusions can be drawn.
CONCLUSION
I was recently asked by a Time magazine reporter, “If we could build a robot or an android that duplicated the processes behind human consciousness, would it actually be conscious?” It is a provocative question and it is one that persists, especially as one tries to capture the differences between the spheres of consciousness of animals and also those that exist between separated left and right brains. Much of what I have written here about bisected brains has appeared before. Yet, I find that the way we all nuance our understanding of complex topics is ever changing, since none of us hold the true answers in our hip pocket. I found myself answering the reporter with what I feel is a new twist.
Underlying this question is the assumption that consciousness reflects some kind of process that brings all of our zillions of thoughts into a special energy and reality called personal or phenomenal consciousness. That is not how it works. Consciousness is an emergent property and not a process in and of itself. When one tastes salt, for example, the consciousness of taste is an emergent property of the sensory system, not of the combination of elements that make up table salt. Our cognitive capacities, memories, dreams, and so on reflect distributed processes throughout the brain, and each of those entities produces its own emergent states of consciousness.
In closing, remember this one fact. A split-brain patient, a human who has had the two halves of his brain disconnected from each other, does not find one side of the brain missing the other. The left brain has lost all consciousness about the mental processes managed by the right brain, and vice versa. It is just as with aging or with focal neurologic disease. We don’t miss what we no longer have access to. The emergent conscious state arises out of each capacity and probably through neural circuits local to the capacity in question. If they are disconnected or damaged, there is no underlying circuitry from which the emergent property arises.
The thousands or millions of conscious moments that we each have reflect one of our networks being “up for duty.” These networks are all over the place, not in one specific location. When one finishes, the next one pops up. The pipe organ-like device plays its tune all day long. What makes emergent human consciousness so vibrant is that our pipe organ has lots of tunes to play, whereas the rat’s has few. And the more we know, the richer the concert.