Consciousness is the state or quality of awareness, or, of being aware of an external object or something within oneself. It has been defined as: sentience, awareness, subjectivity, the ability to experience or to feel,wakefulness, having a sense of selfhood, and the executive control system of the mind. Despite the difficulty in definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is. As Max Velmans and Susan Schneider wrote in The Blackwell Companion to Consciousness: "Anything that we are aware of at a given moment forms part of our consciousness, making conscious experience at once the most familiar and most mysterious aspect of our lives."
Western philosophers, since the time of Descartes and Locke, have struggled to comprehend the nature of consciousness and pin down its essential properties. Issues of concern in the philosophy of consciousness include whether the concept is fundamentally coherent; whether consciousness can ever be explained mechanistically; whether non-human consciousness exists and if so how can it be recognized; how consciousness relates to language; whether consciousness can be understood in a way that does not require a dualistic distinction between mental and physical states or properties; and whether it may ever be possible for computing machines like computers or robots to be conscious, a topic studied in the field of artificial intelligence.
Thanks to recent developments in technology, consciousness has become a significant topic of research in psychology, neuropsychology and neuroscience within the past few decades. The primary focus is on understanding what it means biologically and psychologically for information to be present in consciousness—that is, on determining the neural and psychological correlates of consciousness. The majority of experimental studies assess consciousness by asking human subjects for a verbal report of their experiences (e.g., "tell me if you notice anything when I do this"). Issues of interest include phenomena such as subliminal perception, blindsight, denial of impairment, and altered states of consciousness produced by alcohol and other drugs, or spiritual or meditative techniques.
In medicine, consciousness is assessed by observing a patient's arousal and responsiveness, and can be seen as a continuum of states ranging from full alertness and comprehension, through disorientation, delirium, loss of meaningful communication, and finally loss of movement in response to painful stimuli. Issues of practical concern include how the presence of consciousness can be assessed in severely ill, comatose, or anesthetized people, and how to treat conditions in which consciousness is impaired or disrupted.
What is Consciousness?
Any parent can vouch for just how complicated things become when a child starts reaching the age of hard questions. We’ve all been there:
“Why is the sky blue?”
“Because, honey, the molecules in the air scatter blue light more than other colors.”
“Oh. Where do babies come from?”
“Sperm and egg come together to form a zygote, which develops into a fetus and then a child.”
“Hmm. Is there a God?”
“What about Santa?”
“Why does his breath always smell funny?”
“He uses a special mouthwash from the North Pole.”
“Daddy, what’s consciousness?”
If someone asked you to explain consciousness, could you do it? Very, very smart people have spent their entire careers trying to understand the answer to that question. It is surprising that something we all experience is so hard to explain. The difficulty comes in describing the “what it’s likeness” that characterizes consciousness. There’s something it’s like to experience the color red, to taste chocolate, to feel happy or sad. Philosophers call this phenomenology. Unlike other worldly stuff, it isn’t something we can point to or hold in our hand. It’s not something we’ve been able to calculate. And we’ve yet to find a rigorous method of measuring it.
In 1994 David Chalmers published a paper explaining why consciousness is such a challenging phenomenon to understand. Although he wasn’t the first to discuss these challenges, he was the first to categorize them into two types of problems: “easy” problems and the “hard” problem. Easy problems involve the explanation of how the mind integrates information, focuses attention and allows us to report on mental states. Though not a piece of cake, such problems are easy because solving them only requires that we determine the mechanisms that explain these behaviors. Easy problems are physical by nature, falling within the empirical domains of psychology, cognitive science and neuroscience. Given the current trend in science of the mind, we’re confident that one day we will solve these problems.
The hard problem, by contrast, may never be solved. Specifically, the hard problem is determining why or how consciousness occurs given the right arrangement of brain matter. What makes it hard is that we cannot just point to some physical mechanism to solve it, for that would be the solution to the easy problem. Instead, our goal is to explain why certain physical mechanism gives rise to consciousness instead of something else or nothing at all. Consider an analogy from physics: knowing every equation predicting how mass and gravity interact does not tell us why they interact in the way they do. To understand why mass and gravity interact, we must appeal to highly esoteric explanations involving relativity, quantum mechanics or string theory.
But while theoretical physicists have produced some pretty specific models that are ready to be tested with the likes of the Large Hadron Collider, consciousness lacks the sort of general consensus that would allow us to move on and test our theories. And for good reason—the hard problem is tricky.
Some argue that the hard problem simply is unsolvable. The argument for this view can take two different forms. The first argument is that our puny brains aren’t capable of coming up with a solution, for our brains do not have the ability to process the complicated information that would lead to an understanding of consciousness. The second argument is that a solution to a problem requires that you aren’t a part of the problem. What does this mean? To solve a problem, or so goes the argument, you must have a bird’s eye view of all the facts. But since we are all conscious, we can never have such a view. We simply cannot solve the hard problem because we don’t have access to the level of information necessary to piece everything together.
I think this argument fails, for proponents of this view don’t explain why we cannot come to understand such high concepts through induction. Inductive reasoning is the “bottom-up” logic we often use to construct general belief from individual examples.
One way we use induction every day is when choosing what to wear. We choose a particular type of outfit to wear based on past weather patterns surrounding that morning. If we know the outdoor temperature has been 25 degrees fahrenheit for the last 10 days, we can assume it will be cold outside, thus it is appropriate to put on winter clothes. Of course, you could fail to arrive at a true proposition through induction. For example, if you live in St. Louis sometimes you might find that a 65-degree day follows a 25-degree day. In that case the belief you arrived at through induction is false. You instead should choose spring clothing. But induction seems to work in many cases, especially in the physical and mathematical realms. So it’s unclear why we could not use inductive reasoning to solve the hard problem.
This inductive approach is indeed what many philosophers and cognitive scientists have tried to take. Based on what is known about phenomenal states along with the brains that possess them, many theories of consciousness have emerged, leading to huge debates in philosophy and the sciences. Perhaps the greatest debate has focused the distinction between dualism and physicalism.
Physicalism holds that consciousness is entirely physical. One type of physicalism denies there is a problem at all. For folk in this philosophical camp, called identity theorists, the mental just is the physical, that is, the mental is nothing else than certain physical situation that obtains given certain arrangements of atoms. Why would one want to hold this view? First off, its simplicity is attractive. We need not appeal to “spooky” concepts like emergence to explain what’s going on when we’re conscious. Second, it gives us a really good reason to think that computers can become conscious. If brains are nothing but biological implementations of computers running a certain program, it’s possible that a silicon chip could run the same software as us.
Another theory, functionalism, holds that mental states are constituted by the function or role they play in a given system. Under this view, mental states exist as causal relations to other mental states. Functionalism is especially popular among computationalism, those who believe the brain is just a biological implementation of a computer. According to computationalism the brain is one system physically able to realize mental states, other systems such as computers could also realize these mental states. However functionalism does have its weaknesses. Many philosophers have argued that the theory is insufficient to account for consciousness because the role a mental state plays doesn’t explain why the state must be one that is conscious. It's not clear why all our mental states wouldn't just be processed unconsciously.
Fundamentally different than physicalism, dualism is the theory that consciousness somehow falls outside the domain of the physical. To be a dualist, you need not believe that consciousness is a totally non-physical entity floating about the tops of our physical brains, you simply must believe that the hard problem is not solvable merely through sole appeal to the physical.
There are many types of dualism purported to best solve different aspects of the hard problem. For example, Cartesian dualism, one of the oldest forms of substance dualism, holds that there are both physical and non-physical substances and that consciousness is located within non-physical substance. Another theory, property dualism, holds that consciousness is a non-physical property that emerges from the same things that give rise to physical properties. Property dualists believe that neural activity has both physical and non-physical properties. Physical properties include things like electromagnetic potential while non-physical properties include things like consciousness.
Property dualists can further be distinguished into fundamental, emergence and neutral monist groups. Proposed by Chalmers, fundamental property dualism holds that conscious properties are basic properties of the universe similar to physical properties like electromagnetic charge. According to Chalmers, these properties can interact with other properties such as physical properties, but like fundamental physical properties, conscious properties are their own distinct fundamental entities. Consciousness works like electrical charge or other physical properties do: it may cause physical matter to transition among physical states and these physical states in turn may affect consciousness.
A closely related theory, panpsychism, holds that all aspects of reality have some “psychological” properties apart from their physical properties. This type of property dualism suggests that the universe has consciousness at its base. While this theory certainly is elegant, it is thought by some to carry metaphysical baggage. One complaint has been that, if this theory is true, then all matter would have a certain element of consciousness to it. Because consciousness is inherently connected with the phenomenal, this is a peculiar result, for it’s hard to imagine how there could be something it’s “like” to be an electron, table, chair, tire or other inanimate object.
Furthermore, consciousness seems to have boundaries. There is something that it’s like to be me, to be you and to be someone else. Panpsychism has trouble explaining how phenomenology has a boundary. If consciousness is a fundamental property of matter, it appears as though all matter and collections of matter have a conscious aspect. Collective consciousness entails that, not only do individual electrons have consciousness, so do neurons and collections of neurons. It’s hard to see the level at which you would exist as a conscious being. How many neurons constitute you? Is it one of them, a few of them, all of them? Of course, one might respond that, compared to other problems of consciousness, the boundary problem is rather small. In that case, the elegance of the theory might outweigh its weaknesses.
Like fundamental property dualism, emergent property dualism holds that consciousness is a property that emerges from particular types of physical arrangements of matter. But is differs in that consciousness is a property that emerges over and above what could be predicted given the arrangements of the matter’s physical properties. Yet another type of property dualism, neutral monist property dualism holds that physical and conscious properties are both dependent on some more basic level of reality.
Why would one be motivated to hold one of the above dualist views? What is the need to postulate such spooky entities as non-physical conscious properties? Physicalists have trouble explaining several aspects of consciousness in a way that is consistent with our observations of how physical properties interact.
Frank Jackson’s thought experiment gets at one of the problems of the physicalist approach:
Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal cords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’. [...] What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not?
Jackson argues that Mary in fact will learn something new: what it’s like to see blue. Even though she knows everything about the science of color, she has never experienced color. Jackson later discusses another person, Frank, who experiences a color that no other human has ever seen. It seems that no matter how much information we have about the neural processes behind Frank’s experience of the color, we will never know what it’s like to have Frank’s experience. According to Jackson, that there is something learned only through phenomenal experience shows that experience is not reducible to the purely physical.
Chalmers poses a different problem for physicalism. He tells us to imagine a molecule-by-molecule replica of ourselves, exact down to each individual neuron and its firing state. He then asks to consider whether it’s conceivable that this creature is a philosophical zombie, that is, a creature that is behaviorally indistinct from us but lacking consciousness. Even though on the outside a zombie appears conscious just like you and me, is it possible for it to be “dark” inside? Chalmers says yes. And if that’s the case, he argues, then physicalism must be false. If we admit we can conceive of a world physically indistinct from ours yet lacking phenomenal consciousness, we cannot hold that the mental wholly is based on or reduces to the physical.
But can we really conceive of an exact copy of ourselves that lacks consciousness? On the face of it, most of us would say no. I simply cannot imagine what it would be like to be me without there being anything it’s like to be me. But that’s not what Chalmers is asking us to do. As part of his argument, he makes a distinction between positive and negative conceivability. Positive conceivability means that something is conceivable insofar as you have an imaginative picture of the situation that obtains if the conception were true. But negative conceivability means that something is conceivable insofar as you cannot rule it out a priori, that is, you cannot rule it out from reason alone.
This distinction is crucial for Chalmers’ argument to work. Now all he needs is to get you to admit that reason alone does not provide you with motivation to reject the possibility that your exact physical copy could lack consciousness. Since physicalism holds the physical gives rise to the mental, and because we’ve provided an example of a situation wherein the physical does not give rise to the mental, we must either reject physicalism or reject our negative conception of zombies. Since it isn’t possible to reject the latter, we must reject the former. So physicalism must be false.
Philosophers like Chalmers and Jackson argue that the only appropriate action is to reject physicalism and move in the direction of dualism. These arguments have gotten much attention in the literature from authors on both sides of the debate. And many objections have arisen.
In response to Jackson, Laurence Nemirow argues that knowing what it’s like to have an experience is the same thing as knowing how to imagine having the experience. In Mary’s case, she didn’t learn something new, she just gained the ability to experience color. David Lewis makes a similar argument: Mary gained the ability to remember, imagine and recognize.
Earl Conee makes a slightly different argument: knowing what it’s like does not require having an imaginative experience. He introduces Martha, who is able to visualize intermediate shades of colors she has not experienced that fall between pairs of shades that she has experienced. Martha is not familiar with the shade of “cherry red” but knows that cherry red is halfway between burgundy red and fire red, two shades she has experienced. According to Conee, Martha could know what it’s like to experience cherry red, but so long as she never imagined it, she might never have experienced that color.
Interestingly, Jackson himself changed his mind several times as to the implications of the Mary argument. Although the argument appeared to offer a strong problem for physicalism, he also believed that all behavior is caused by physical forces. Given that the argument seemed to prove the existence of non-physical phenomenology, Jackson needed to find a way square it away with his conception of the physical. His strategy was to argue for epiphenomenalism, which holds that phenomenal states are caused by physical states, but phenomenal states do not affect the physical. Epiphenomenalism means that our phenomenal states are akin to movies that constantly play while unconscious brain processes direct all behavior.
Later on, Jackson decided that Mary’s conscious recognition of color did have an effect on the physical: it made her say “wow.” If a conscious recognition could be the cause for an expression requiring, which requires a change in mental states, then consciousness appears to play some role in guiding our behavior. So epiphenomenalism would be false. He argued that physicalism could in fact account for this “wow” experience. If the color experience is entirely contained within in the brain, it’s possible that a new experience can cause further changes to the brain, resulting in the utterance of a “wow” statement. He used the analogy of akinetopsia, a deficit that causes the inability to perceive motion. He argued that someone cured of this condition would not discover anything new about the world (since she knows about motion). Instead, surprise would be the response of a brain now able to see motion.
Chalmers’ zombie argument has been subject to scrutiny as well. Because it’s logically valid, that is, because evaluation of the argument’s premises do lead it its conclusion, one must attack the premises in order to undermine the argument. One objection has been that the zombie argument undermines itself. Because the argument builds a world that is defined entirely physically, the world necessarily would contain consciousness; therefore zombies cannot exist in it. Other philosophers attack negative conceivability. They argue that the mere possibility of something does not mean it actually exists. Although zombie worlds might be possible, it is still the case in this world that consciousness is entirely physical.
So which theory wins? Dualism or physicalism? It depends on who you ask. Many empirical researchers are hardcore physicalists, but not all are. The answer to this question will require more insight into the fundamental structure of our physical world. It might turn out that a really consistent theory of physics could lead us to understand exactly what consciousness is. But it might not. Consciousness might forever remain a mystery.
I was in the audience watching a magic show. Per protocol a lady was standing in a tall wooden box, her smiling head sticking out of the top, while the magician stabbed swords through the middle.
A man sitting next to me whispered to his son, “Jimmy, how do you think they do that?”
The boy must have been about six or seven. Refusing to be impressed, he hissed back, “It’s obvious, Dad.”
“Really?” his father said. “You figured it out? What’s the trick?”
“The magician makes it happen that way,” the boy said.
The magician makes it happen. That explanation, as charmingly vacuous as it sounds, could stand as a fair summary of almost every theory, religious or scientific, that has been put forward to explain human consciousness.
What is consciousness? What is the essence of awareness, the spark that makes us us? Something lovely apparently buried inside us is aware of ourselves and of our world. Without that awareness, zombie-like, we would presumably have no basis for curiosity, no realization that there is a world about which to be curious, no impetus to seek insight, whether emotional, artistic, religious, or scientific. Consciousness is the window through which we understand.
The human brain contains about one hundred billion interacting neurons. Neuroscientists know, at least in general, how that network of neurons can compute information. But how does a brain become aware of information? What is sentience itself?
The first known scientific account relating consciousness to the brain dates back to Hippocrates in the fifth century b.c. At that time, there was no formal science as it is recognized today. Hippocrates was nonetheless an acute medical observer and noticed that people with brain damage tended to lose their mental abilities. He realized that mind is something created by the brain and that it dies piece by piece as the brain dies. A passage attributed to him summarizes his view elegantly:
"Men ought to know that from the brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears. Through it, in particular, we think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant."
The importance of Hippocrates’s insight that the brain is the source of the mind cannot be overstated. It launched two and a half thousand years of neuroscience. As a specific explanation of consciousness, however, one has to admit that the Hippocratic account is not very helpful. Rather than explain consciousness, the account merely points to a magician. The brain makes it happen. How the brain does it, and what exactly consciousness may be, Hippocrates left unaddressed. Such questions went beyond the scope of his medical observations.
Two thousand years after Hippocrates, in 1641, Descartes proposed a second influential view of the brain basis of consciousness. In Descartes’s view, the mind was made out of an ethereal substance, a fluid, that was stored in a receptacle in the brain. He called the fluid rescogitans. Mental substance. When he dissected the brain looking for the receptacle of the soul, he noticed that almost every brain structure came in pairs, one on each side. In his view, the human soul was a single, unified entity, and therefore it could not possibly be divided up and stored in two places. In the end he found a small single lump at the center of the brain, the pineal body, and deduced that it must be the house of the soul. The pineal body is now known to be a gland that produces melatonin and has nothing whatsoever to do with a soul.
Descartes’ idea, though refreshingly clever for the time, and though influential in philosophy and theology, did not advance the scientific understanding of consciousness. Instead of proposing an explanation of consciousness, he attributed consciousness to a magic fluid. By what mechanism a fluid substance can cause the experience of consciousness, or where the fluid itself comes from, Descartes left unexplained— truly a case of pointing to a magician instead of explaining the trick.
One of the foundation bricks of modern science, especially modern psychology, is a brilliant treatise so hefty that it is literally rather brick-like, Kant’s A Critique of Pure Reason, published in 1781. In Kant’s account, the mind relies on what he termed “a priori forms,” abilities and ideas within us that are present first before all explanations and from which everything else follows. On the subject of consciousness, therefore, Kant had a clear answer: there is no explaining the magic. It is simply supplied to us by divine act. Quite literally, the magician did it.
Hippocrates, Descartes, and Kant represent only three particularly prominent accounts of the mind from the history of science. I could go on describing one famous account after the next and yet get no closer to insight. Even if we fast-forward to modern neuroscience and examine the many proposed theories of consciousness, almost all of them suffer from the same limitation. They are not truly explanatory theories. They point to a magician but do not explain the magic.
One of the first, groundbreaking neurobiological theories of consciousness was proposed in 1990 by the scientists Francis Crick (the co-discoverer of the structure of DNA) and Christof Koch. They suggested that when the electrical signals in the brain oscillate they cause consciousness. The idea goes something like this: the brain is composed of neurons that pass information among each other. Information is more efficiently linked from one neuron to another, and more efficiently maintained over short periods of time, if the electrical signals of neurons oscillate in synchrony. Therefore, consciousness might be caused by the electrical activity of many neurons oscillating together.
This theory has some plausibility. Maybe neuronal oscillations are a precondition for consciousness. But note that, once again, the hypothesis is not truly an explanation of consciousness. It identifies a magician. Like the Hippocratic account, “The brain does it” (which is probably true), or like Descartes’s account, “The magic fluid inside the brain does it” (which is probably false), this modern theory stipulates that “the oscillations in the brain do it.” We still don’t know how. Suppose that neuronal oscillations do actually enhance the reliability of information processing. That is impressive and on recent evidence apparently likely to be true. But by what logic does that enhanced information processing cause the inner experience? Why an inner feeling? Why should information in the brain—no matter how much its signal strength is boosted, improved, maintained, or integrated from brain site to brain site—become associated with any subjective experience at all? Why is it not just information without the add-on of awareness?
For this type of reason, many thinkers are pessimistic about ever finding an explanation of consciousness. The philosopher Chalmers, in 1995, put it in a way that has become particularly popular. He suggested that the challenge of explaining consciousness can be divided into two problems. One, the easy problem, is to explain how the brain computes and stores information. Calling this problem easy is, of course, a euphemism. What is meant is something more like the technically possible problem given a lot of scientific work. In contrast, the hard problem is to explain how we become aware of all that stuff going on in the brain. Awareness itself, the essence of awareness, because it is presumed to be nonphysical, because it is by definition private, seems to be scientifically unapproachable. Again, calling it the hard problem is a euphemism; it is the impossible problem. We have no choice but to accept it as a mystery. In the hard-problem view, rather than try to explain consciousness, we should marvel at its insolubility.
The hard-problem view has a pinch of defeatism in it. I suspect that for some people it also has a pinch of religiosity. It is a keep-your- scientific-hands-off-my-mystery perspective. One conceptual difficulty with the hard-problem view is that it argues against any explanation of consciousness without knowing what explanations might arise. It is difficult to make a cogent argument against the unknown. Perhaps an explanation exists such that, once we see what it is, once we understand it, we will find that it makes sense and accounts for consciousness.
The current scientific study of consciousness reminds me in many ways of the scientific blind alleys in understanding biological evolution. Charles Darwin published his book The Origin of Species in 1859, but long before Darwin, naturalists had already suspected that one species of animal could evolve into another and that different species might be related in a family tree. The idea of a family tree was articulated a century before Darwin, by Linnaeus, in 1758. What was missing, however, was the trick. How was it done? How did various species change over time to become different from each other and to become sophisticated at doing what they needed to do? Scholars explored a few conceptual blind alleys, but a plausible explanation could not be found. Since nobody could think of a mechanistic explanation, since a mechanistic explanation was outside the realm of human imagination, since the richness and complexity of life was obviously too magical for a mundane account, a deity had to be responsible. The magician made it happen. One should accept the grand mystery and not try too hard to explain it.
Then Darwin discovered the trick. A living thing has many offspring; the offspring vary randomly among each other; and the natural environment, being a harsh place, allows only a select few of those offspring to procreate, passing on their winning attributes to future generations. Over geological expanses of time, increment by increment, species can undergo extreme changes. Evolution by natural selection. Once you see the trick behind the magic, the insight is so simple as to be either distressing or marvelous, depending on your mood. As Huxley famously put it in a letter to Darwin, “How stupid of me not to have thought of that!”
The neuroscience of consciousness is, one could say, pre-Darwinian. We are pretty sure the brain does it, but the trick is unknown. Will science find a workable theory of the phenomenon of consciousness?
I propose a theory of consciousness that I hope is unlike most previous theories. This one does not merely point to a magician. It does not merely point to a brain structure or to a brain process and claim without further explanation, ergo consciousness. Although I do point to specific brain areas, and although I do point to a specific category of information processed in a specific manner, I also attempt to explain the trick itself. What I am trying to articulate is not just, “Here’s the magician that does it,” but also, “Here’s how the magician does it.”
For more than twenty years I studied how vision and touch and hearing are combined in the brain and how that information might be used to coordinate the movement of the limbs. I summarized much of that work in a previous book, The Intelligent Movement Machine, in 2008. These scientific issues may seem far from the topic of consciousness, but over the years I began to realize that basic insights about the brain, about sensory processing and movement control, provided a potential answer to the question of consciousness.
The brain does two things that are of particular importance to the present theory. First, the brain uses a method that most neuroscientists call attention. Lacking the resources to process everything at the same time, the brain focuses its processing on a very few items at any one time. Attention is a data-handling trick for deeply processing some information at the expense of most information. Second, the brain uses internal data to construct simplified, schematic models of objects and events in the world. Those models can be used to make predictions, try out simulations, and plan actions.
What happens when the brain inevitably combines those two talents? In theory, awareness is the brain’s simplified, schematic model of the complicated, data-handling process of attention. Moreover, a brain can use the construct of awareness to model its own attentional state or to model someone else’s attentional state. For example, Harry might be focusing his attention on a coffee stain on his shirt. You look at him and understand that Harry is aware of the stain. In the theory, much of the same machinery, the same brain regions and computational processing that are used in a social context to attribute awareness to someone else, are also used on a continuous basis to construct your own awareness and attribute it to yourself. Social perception and awareness share a substrate. The attention schema theory, as I eventually called it, takes a shot at explaining consciousness in a scientifically plausible manner without trivializing the problem.
The theory took rough shape in my mind (in my consciousness, let’s say) over a period of about 10 years.
A great many reaction pieces were published by experts on the topic of mind and consciousness and a great many more unpublished commentaries were communicated to me. Many of the commentaries were enthusiastic, some were cautious, and a few were in direct opposition. I am grateful for the feedback, which helped me to further shape the ideas and their presentation. It is always difficult to communicate a new idea. It can take years for the scientific community to figure out what you are talking about, and just as many years for you to figure out how best to articulate the idea.
None of us knows for certain how the brain produces consciousness, but the attention schema theory looks promising. It explains the main phenomena. It is logical, conceptually simple, testable, and already has support from a range of previous experiments. I do not put the theory in opposition to the three or four other major neuroscientific views of consciousness. Rather, my approach fuses many previous theories and lines of thought, building a single conceptual framework, combining strengths. For all of these reasons, I am enthusiastic about the theory as a biological explanation of the mind—of consciousness itself—and I am eager to communicate the theory properly.
What is consciousness? A scientist’s perspective.
We all know what consciousness is. We can tell when we’re awake, when we’re thinking, when we’re pondering the universe, but can anyone really explain the nature of this perception? Or even what separates conscious thought from subconscious thought?
Historically any debate over the nature of consciousness has fallen to philosophers and religious scholars rather than scientists. However, as our understanding of the brain increases so do the number of scientists willing and able to tackle this tricky subject.
What is consciousness?
A good analogy of consciousness is explained here based on work by Giulio Tononi. Imagine the difference between the image of an apple to your brain and a digital camera. The raw image is the same whether on a camera screen or in your head. The camera treats each pixel independently and doesn’t recognise an object. Your brain, however, will combine parts of the image to identify an object, that it is an apple and that it is food. Here, the camera can be seen as ‘unconscious’ and the brain as ‘conscious’.
The bigger the better?
This example works as a simple analogy of how the brain processes information, but doesn’t explain the heightened consciousness of a human in comparison to say a mouse. Some people believe that brain size is linked with consciousness. A human brain contains roughly 86 billion neurons whereas a mouse brain contains only 75 million (over a thousand times less). A person might then argue that it is because our brains are bigger and contain more nerve cells that we can form more complex thoughts. While this may hold to a certain extent, it still doesn’t really explain how consciousness arises.
To explain why brain size isn’t the only thing that matters, we need to consider our brain in terms of the different structures/areas it consists of and not just as a single entity. The human cerebellum at the base of the brain contains roughly 70 billion neurons, whereas the cerebral cortex at the top of the brain contains roughly 16 billion. If you cut off a bit of your cerebellum (don’t try this at home) then you may walk a bit lopsided, but you would still be able to form conscious thoughts. If however, you decided to cut off a bit of your cortex, the outer-most folds of the brain, your conscious thought would be severely diminished and your life drastically impacted. So it seems that the number of brain cells we have doesn’t necessarily relate to conscious thought.
As a general rule the more primal areas of the brain, such as the brain stem and cerebellum act a bit like the camera. Like the camera, they are purely responsible for receiving individual pieces of information from our sensory organs and don’t care for linking this information together. As you move higher up the brain, links form between different aspects of our sensory experiences. This linking begins in mid-brain structures (such as the thalamus) then these links are made more intricate and permanent in the cerebrum.
Tononi believes that it is this linking of information that is the basis for consciousness. As cells become more interlinked, information can be combined more readily and therefore the essence of complicated thought can be explained. The more possible links between cells, the more possible combinations there are and therefore a greater number of ‘thoughts’ are possible.
There may be more neurons in the cerebellum than the cerebrum, but because they are not as extensively linked to each other, they cannot form as complicated thoughts as the cerebrum. When information is relayed upwards from the cerebellum in the brain, it is passed to neurons that have more connections and can therefore make more abstract links. Perhaps a neuron responsible for telling the colour red links with a neuron responsible for the representation of a round object, giving you the notion of a red apple. If you multiply this process up a couple of times, cells soon hold a lot of combined information – smell, taste, colour etc. all come together to create your representation of the apple.
Too much connectivity
So it’s the number of connections that matter? The more connections the better? Well no, sadly it’s not quite that simple. The cells at the higher levels need to be highly interconnected but if all the cells in the brain were too interconnected then you would really be back to square one, where the whole system is either on or off. All the cells fire, or none of them do. Here, you lose all specific information and your brain doesn’t know whether it is red or round or anything, it just knows there’s something. Because along with your red apple cells, all your blue cells will fire, all your bicycle cells will fire and so on, meaning you’ll get no clear information about the apple whatsoever.
The key is that cells at the basic level need to be focused and not have their message conflicted by other information. They then pass their message up to a more connected cell that combines it with other information before passing it up a level, and so on and so forth. Now we have an entity that can build up complicated information from small bits. According to Tononi it is the ability to combine lots of information efficiently that yields the ability to analyse abstract concepts and thus gives us ‘consciousness’.
How do we become unconscious?
The true test of how good a theory of consciousness this is is whether it can also explain a loss of consciousness. Tononi believes that unconsciousness is brought on when the system becomes fragmented and connectivity in the brain decreases. This is exactly what seems to happen when in a deep sleep (when we don’t dream) or under general anaesthetic. Normally when awake and alert, fast activity can be found all over the brain and signals can be passed between areas. When we go into a deep sleep however, the brain moves to a state where signals cannot easily pass between different areas. Tononi believes that the cells temporarily shut off their connections with each other in order to rest and recuperate, therefore losing interconnectivity and associated higher thought processes.
While it may seem a far reach to suggest that consciousness is purely a state of high interconnectivity, what Tononi has done is to present the beginnings of a tangible scientific theory, backed by evidence that suggests interconnectivity is crucial for higher brain power. The question of why we can form conscious thoughts is more of a philosophical one but the scientific view seems to be that it is a fundamental property of our brains. The evolution of man has led our brains to become highly efficient at processing complex information, giving us a vast repertoire of possible thoughts. This repertoire has expanded to such an extent that we can now debate our very existence and purpose. Whatever you believe about the reasons behind consciousness, however, scientists are beginning to have their say about what rules may govern consciousness in the brain.
What does it mean to be conscious? It's a question that philosophers and scientists have puzzled over perhaps since there have been philosophers and scientists.
In his book "Consciousness Explained," Tufts University philosopher Daniel Dennett calls human consciousness "just about the last surviving mystery," explaining that a mystery is something that people don't yet know how to think about. "We do not yet have all the answers to any of the questions of cosmology and particle physics, molecular genetics and evolutionary theory, but we do know how to think about them," writes Dennett. "With consciousness, however, we are still in a terrible muddle. Consciousness stands alone today as a topic that often leaves even the most sophisticated thinkers tongue-tied and confused. And, as with all of the earlier mysteries, there are many who insist—and hope—that there will never be a demystification of consciousness."
On a base level, consciousness is the fact of being awake and processing information. Doctors judge people conscious or not depending on their wakefulness and how they respond to external stimuli. But being conscious is also a neurological phenomenon, and it is part of what allows us to exist and understand ourselves in the world.
Dr. Antonio Damasio, a neuroscientist from the University of Southern California who has studied the neurological basis of consciousness for years, tells Big Think that being conscious is a "special quality of mind" that permits us to know both that we exist and that the things around us exist. He differentiates this from the way the mind is able to portray reality to itself merely by encoding sensory information. Rather, consciousness implies subjectivity—a sense of having a self that observes one’s own organism as separate from the world around that organism.
"Many species, many creatures on earth that are very likely to have a mind, but are very unlikely to have a consciousness in the sense that you and I have," says Damasio. "That is a self that is very robust, that has many, many levels of organization, from simple to complex, and that functions as a sort of witness to what is going on in our organisms. That kind of process is very interesting because I believe that it is made out of the same cloth of mind, but it is an add-on, it was something that was specialized to create what we call the self."
Scientists don't fully understand what is happening in the brain that creates what we call consciousness, but researchers like Damasio are refining our knowledge about how firing neurons can lead to our thoughts and experience of the world.
Twelve years ago, Cal Tech professors Christof Koch and Francis Crick put forward the idea that consciousness resides in the brain's prefrontal cortex; they described where in the brain we experience things when we experience them—but not why we do. In 2009, physicist Roger Penrose and anesthesiologist Stuart Hamerhoff advanced a "quantum mind theory" that took Koch and Crick's ideas to a deeper, cellular level, suggesting that consciousness is a result of quantum mechanics, with microtubules inside the brain working as computing elements in a system they call "orchestrated objective reduction." The theory suggests that human consciousness is a result of the wave functions of quantum particles collapsing once they reach specific energy levels. Hamerhoff's blog, Quantum Consciousness, describes this theory in depth, and details how he and Penrose believe the brain's neural networks and cells process information that results in consciousness. Critics of the quantum mind theory contend that consciousness is hardly demystified by relating the brain to the rarefied realm of subatomic physics.
One thing to keep in mind is that consciousness is not uniform among humans, according to Damasio. Different people may experience consciousness in different ways, and it can be difficult to make comparisons of people's subjective perceptions of reality with very much detail. Nonetheless, he notes: "When you look at people that say, from the same culture, roughly the same age, and not very difference intelligence, and you make a lot of detailed questions about the experiences of say colors, situations, and so on, you’ll get very similar answers. So I think it’s reasonable to say that even though, in all likelihood, we have slightly different experiences of reality, they are similar enough to us not to clash."
Studies of consciousness don't all center on wakefulness. Dr. Sam Parnia, director of the Human Consciousness Project, embarked in 2008 on a three-year, 1500-patient quest to try and figure out whether people continue to be conscious when their bodies are clinically dead. Analyzing reports of near-death experiences when patients are in cardiac arrest, the project is seeking quantifiable data about what happens in a person's brain when oxygenated blood stops flowing, and whether we then continue to think consciously.
What we call consciousness is the fact of our having a subjective experience of the world—it is our sense that the world is separate from us, and that we exist independently. While it is unclear exactly how neural firings in specific parts of the brain result in this kind of subjective thought, it's believed that conscious thinking is related to the prefrontal cortex—and possibly extends down to a cellular level.