Friday, January 20, 2006

Part 6: Why?

I mean that. Why? Why all this? Why anything at all? Why does the universe exist, and why is it the way it is? Why do heavy objects attract each other? Why are atoms made of protons, neutrons and electrons? Why are the laws of physics as they are instead of being even slightly different? If you think about the question of consciousness, it is very much related to the big question of Why. "What is consciousness?", or "Why consciousness?", are sub-questions of the big Why. Why this universe?

I think the question is not as grandiose as it seems, and the answer is fairly simple. It's all about conditional probability. I hear the following (or a similar) story on the news almost every day. Say, they are interviewing a lady in the hospital. She is in a body cast, with limbs supported by ropes, and can barely speak. "Can you tell us what happened?" asks the reporter. "I was crossing the street," she says, "looking at my watch, and I was hit by a car." She adds, "Thankfully, the car turned out to be an ambulance, and they brought me straight here." The reporter turns to the paramedic, "It is great that you were right there!" "Yes," he replies, "she is very lucky to be alive right now."

Sure it's a cheesy story, but there is one word in it that always puzzles me - lucky. Why is she lucky to be alive? I wouldn't feel lucky at all being in her position. That word has always sounded strange until it occurred to me - conditional probability! Yes, given that she was hit by a car, she is very lucky that the car turned out to be an ambulance. Of all the people who have been hit by cars, she is surely lucky. However, given that she was crossing the street, she is quite unfortunate to have been hit by a car in the first place. Given that it is raining, it's not surprising that people are carrying umbrelas. However, given that you are in southern California, seeing a person with an umbrela is quite a rarity.

So what does this have to do with Why? Conditional probability immediately answers the question Why are we, humans, here? It's trivial. We exist, and given that we exist, it is not surprising that we would be asking this question. Why are we on Earth instead of the 4th planet of Alpha Centauri? Well, given that we exist, we've got to exist somewhere. Were we on Alpha Centauri, we would be asking the same question there. Why does the universe exist? Well, if it didn't, we would not be asking this question. Given that we are asking the question, we surely exist, and so does the universe. Why is it so beautiful and magnificent, with such specific laws? Why does the colour green look the way it does? Well, given that the universe exists, it might as well exist the way it exists now. Once again, were it any different, we would be asking the same questions. Perhaps, there are uncountably many universes, all different, all with strange conscious creatures wondering why their universe is the way it is.

What I am saying is that, for the most part, there is nothing special about our universe in the way it is. Out of all the Why questions a child may ask after looking at the world around her, only very few are even remotely interesting. It is not interesting why green is green. Questions that are worth asking are those not explained by conditional probability. For instance, why is there more matter than antimatter in the visible universe? That is something we would not expect to see, even given that the universe exists and is the way it is. The question of why there is life on Earth and not Mars, Venus or some other planet in our galaxy is not interesting. Given that humans are in the Solar system, Earth is the only planet with a surface temperature that can support liquid water and, hence, mild climates. As for the planets outside our Solar system, who knows? Occam's razor says there should be intelligent life all over the place. Too bad the speed of light is so darn small. Until we find a way to travel to other stars, we should not assume that there is no life there. For now, there is nothing special about Earth, as far as we can tell.

The reason I have brought this up is that I am not convinced by people who claim that consciousness, and life itself, must be a sign of a higher power. "Look at the world;" they say, "is it not too wonderous and magnificent to have appeared by chance?" There is no chance! It is not like there was a choice of a billion possible worlds, most of which were ugly, and someone or something chose this particular world. Perhaps there was, but that is immaterial and unprovable at this point in time. The fact is - we are here, alive and intelligent. And given that we are here, alive and intelligent enough to ask this question, the existence of humans, life and intelligence is no coincidence at all - it is inevitable. I would be infinitely surprised if I were here and there were no life on Earth. Then I would wonder about how lucky I was to be on this particular planet, alive and (somewhat) intelligent. Otherwise, given any conscious being able to ask the question, "Why am I here?", the answer is obvious - because you are asking that question, here.

Thursday, January 19, 2006

Part 5: Quantum epiphanies

One of the most famous theories of consciousness is that of Sir Roger Penrose and Dr. Stuart Hameroff - a mathematical physicist and an anesthesiologist. As their theory is at best revolutionary and at worst crazy, I will approach the fascinating subject from afar.

Quantum mechanics. Often regarded as the most successful development in all of modern physics, quantum mechanics is basically a theory that explains how the elementary particles (electrons, protons, neutrons, photons, etc.) behave. At the turn of the 20th century, a new theory was needed, as classical physics would fail on the very small scale of electrons and photons. Through the work of Bohr, Heisenberg, Schrödinger, Pauli and others, the theory of quantum mechanics was born. This theory is able to predict with incredible accuracy the outcomes of numerous physical experiments that cannot be explained by classical physics. Quantum mechanics is correct; it is tried and tested. The only situations where it gets into trouble are inside black holes and during the first fractions of a second after the Big Bang, neither of which have much to do with our study of consciousness.

As successful as it is, quantum mechanics is very strange. First of all, it is entirely based on probability - a dubious mathematical concept. (When asked to define "probability", mathematicians often quote the Law of Large Numbers, which, of course, "defines" probability in terms of itself.) Albert Einsten, often quoted as saying, "[God] does not throw dice," was an early opponent of quantum mechanics because of its basis in probability.

However, probability is just the beginning of the weirdness that is quantum mechanics. The core principle behind the Penrose-Hameroff theory of consciousness is a phenomenon called quantum superposition. The mathematics behind quantum mechanics says that if a particle (for example, a photon) has a probability of being in one of two distinct states, then in some cases, it can be in the two states simultaneously. For example, we can set up a laser and aim it at a half-silvered mirror. Half the light beam will be reflected by the mirror at a 90-degree angle, and half the beam will pass through the mirror. We can then dim down the laser to a point when it starts shooting single photons, say, one per second. Each photon will have a 50% probability of being reflected and a 50% probability of passing through the mirror. Quantum superposition says that, under certain conditions, it is possible for the photon to be both reflected and not reflected at the same time. As long as there is no interaction between the photon and the outside world, the two states can exist at the same time - a phenomenon called quantum entanglement. However, as soon as we attempt to detect whether the photon went through the mirror or got reflected, quantum entanglement is broken, and the photon collapses to one of the two states.

To illustrate how weird this theory is, Erwin Schrödinger described his famous Schrödinger's cat thought experiment. Suppose that we put the laser and the mirror into a box with two holes - one for each of the possible exit paths of the photon. To one of the holes, we attach a device that fires a gun whenever a photon is detected. The gun is pointed at a cat. Now, whenever a photon is fired from the laser, quantum entanglement says that it is both reflected and not reflected, which means that the gun both fires and does not fire, which, in turn, means that the cat is both dead and alive. Eventually, a physicist comes into the room and looks at the cat, at which point the quantum state collapses into one of the two possibilities, and the physicist either sees a dead cat or a happy cat. There are some technical details; for example, the whole contraption has to be isolated from the outside environment so that the quantum entanglement can be preserved, but the point of the thought experiment is to illustrate the inherently weird nature of quantum mechanics.

One of the most interesting and puzzling properties of quantum superposition is that an observer causes the quantum state to collapse. In a sense, superposition is an "undecided state", and the observer causes a decision to be made. There is that word again - decision. Perhaps there is a connection between consciousness and quantum superposition collapse. What is it inside our neurons that causes consciousness? And what is so special about neurons anyway, especially if we assume that bugs and bacteria are conscious, too? What if consciousness is really a quantum mechanical property, and biology is simply a "bridge" between the strange microscopic quantum world and the macroscopic world of classical physics? Electrons and photons in superposition states make decisions all the time, but we do not see any of their effects because they cannot create a noticeable change in the macroscopic world. Biology, however, has found a way to build an amplification device - life - that allows microscopic events to have large-scale consequences. For example, when I think of lifting my arm, there is a decision being made at the quantum level, and through the electro-chemical signals, that decision has an enormous (compared to the quantum scale) effect - my muscles contract and lift my arm.

What if the cat's life or death is a decision made by the photon after it has passed through the half-mirror? For a certain short period of time, the photon is in superposition - the undecided state. Then, an observer opens the box, and the decision is made - superposition collapses to one of the two possibilities. Perhaps it is not the photon itself that makes the decision, but the observer, or the cat. In any case, the two spooky notions - consciousness and superposition - seem to have something in common. Opponents of the Penrose-Hameroff theory dismiss it as simply replacing one weird concept (consciousness) by another (quantum mechanics) without explaining anything. That is not true; we know quite a bit about quantum mechanics. For one, we can make predictions and devise experiments to test them. So far, however, no one has come up with a way to definitively prove or disprove the existence of a connection between decision making and quantum superposition.

Is such a thing even possible - maintaining a superposition state in the brain? Superposition requires complete isolation from the outside environment and extremely low temperatures. Nevertheless, Hameroff claims that there is a place in the brain where superposition is possible for periods of time on the order of milliseconds, which is about the right time it takes humans to make a decision. That place is inside microtubules - tiny pipes inside a neuron that are made of proteins. Anesthetics (drugs that make you "lose consciousness") act on the microtubules in neurons.

In essense, the Penrose-Hameroff theory says that consciousness is everywhere. It is a fundamental physical property. Biological organisms are not the source of consciousness; they are merely nature's attempt at understanding itself by providing a bridge between the quantum world and the macroscopic world. The universe itself is conscious. In fact, one of the most fascinating unanswered questions in physics is the question of why we have asymmetry in the world. Why is all of the known universe made of matter and not anti-matter? Why do we have stars, galaxies and black holes - clumps - instead of a uniformly smeared cloud of "stuff" everywhere? One hypothesis is that just after the Big Bang, the whole universe was in quantum superposition - everything existed at once. But then at some point there was a collapse - the Big Wow - that moment when the Universe became aware of itself.

Perhaps the Universe has been trying to understand itself ever since, and through evolution, it has developed us - humans - as one of the tools for self-understanding. As far as theories go, in my view, this one is remarkable. On the one hand, it is tied into the core of physics, yet it says nothing of the existence of "true" free will and even leaves open the possibility of a God, a supreme being in the form of the very Universe. There is great debate about the assumptions at the foundation of the theory, as there should be. There are scientists trying hard to find experimental evidence for or against it, and there are those who outright dismiss it as complete rubbish, claiming that it resolves nothing. I hope that you can find a corner in your mind for this piece of the puzzle. Maybe it will fit into place later, maybe not.

Thursday, January 12, 2006

Part 4: The "no magic" theory

I will start my survey of the theories of consciousness with materialism - the "no magic" theory. Materialism is the child of scepticism and a scientific principle called Occam's Razor, which says that of all the plausible theories, the simplest one is prabably correct. "Simplest" here refers to the number of assumptions made by the theory. In the context of consciousness, materialism is often referred to as eliminative materialism, a term associated with Paul and Patricia Churchland.

A true materialist believes that since over the course of millenia, we have found no evidence for the existence of "God", or "souls", or "supreme beings" of any kind, then those things do not exist. The only things that do exist are material - that is, made of matter. Tables are made of matter, and humans are made of matter. There is no reason to assume that consciousness (whatever it is) is not made of matter also. Note that matter in this sense includes energy. In fact, let's use the word "matter" to denote anything that can be detected and measured by physical instruments.

If consiousness is material, then it is located in the brain. That is because you can replace almost every other part of your body without it affecting your consciousness. Well, what are the things we have in our brains? There is the neocortex, which is responsible for building abstractions and interacting with our senses, speech and motor functions. There is the "old brain" - everything that is inside the cortex - which is responsible for things like our instincts. And then there is this strange thing called consciousness that seems to be responsible for making all of our decisions. We cannot detect a "soul"; therefore, it is not there.

According to materialists, such phenomena as belief, intention and love can be explained in terms of physical and chemical processes that occur in the brain. Given enough time, scientific advances will let us understand everything about the basic functions of the brain. Long before that, we will understand completely how simpler organisms work. Take, for example, a virus. There is debate among scientists whether a virus is a living organism. Why is that? It is probably because we already understand a great deal about how a virus operates. A Hepatitis C virus is a tiny ball made up of about 10 different kinds of RNA molecules. We know how it reproduces by infecting living cells. We know most of the chemical reactions that are involved. In some sense, adding a virus to a living cell is no different from adding vinegar to baking soda - there will be a chemical reaction, and we know its outcome. There is nothing special about it. A materialist would say that eventually we will be able to understand humans as well as we understand virii.

The main consequence of this theory is the absence of free will. In short, we are all pieces in a game whose rules are the rules of nature, and our whole life is predetermined from birth to death. All of the decisions that we make have already been made, and our choices in life are merely an illusion. Consiousness is an illusion. Although there are some scientists who try to remain materialistic while side-stepping the issue of free will, it is very difficult to avoid making this conclusion.

Consequently, the main argument against materialism attacks the absense of free will. First of all, people find depressing the suggestion that they have no control over their own life. If that is so, then why should we try? Why not quit our jobs, relax and have fun in life? It's all pre-determined anyway. I think that this line of reasoning is a mistake. So what if free will is an illusion? Since we cannot predict the future, it does not matter that our whole life story has already been written. Since there is no way we can read the story's ending, the fact that free will is an illusion is inconsequential. My decisions clearly have consequences. I'm not jumping out of the window because I know that the outcome will be unfavourable. As far as I can tell, my decisions have consequences, and that is what matters.

So what is the mechanism behind decision-making? Here is a thought. As I have mentioned above, the brain has consciousness (for making decisions), intelligence (for allowing us to operate with abstract concepts) and instincts. What are instincts? First of all, we have the survival instinct. Why do we have it? Simple. Evolution. Any species that didn't have the survival instinct didn't survive very long. Next, we have sexual instincts. Same deal - evolution. I claim (and I'm sure that I'm not the first one to claim) that every desire that you have is the result of some instinct. We have instincts that drive us to try and understand the world around us, instincts to be a good person and make the lives of those around us better, etc. Some of these are the result of evolution, some are imposed by society and family, and some just seem random (different people can have diametrically opposite instincts).

So in the spirit of Occam's razor, here is a dead-simple theory of consciousness. Our large set of instincts defines an extremely complicated "objective function", and every decision that we make in our life is meant to optimise this function. The cortex plays a big role in it because, first of all, it allows us to operate with very vaguely defined instincts in terms of highly abstract concepts. And second of all, it allows us to evaluate the objective function. Remember Jeff Hawkins' memory-prediction framework, where sensory inputs flow up the cortex hierarchy and predictions flow down? Now suppose that you are faced with a decision. Then the cortex can predict what would happen as a result of deciding A and what would happen as a result of deciding B. In both cases, your brain would evaluate the effect on the objective function and choose the better option.

For the mathematically inclined, what I am claiming is that consciousness is the process of optimising an objective function using a brain, where the objective function is given as a complicated weighted combination of our instincts, and the optimization is done using the forward Euler method performed in the neocortex. Obviously, the no free will objection is still valid, but the main afgument for this theory is that it is extremely simple and does not rely on voodoo concepts like "elementary particles of conciousness" and "microtubular bridges between the quantum world and the classical world". Of course, those concepts are fascinating, and I will get to them shortly.

Sunday, January 08, 2006

Part 3: Consciousness and free will

The problem of defining consciousness seems to be much trickier than that of defining intelligence, so let's start slow. Before I talk about the many theories that try to explain where consciousness comes from, it would be nice to have some agreement on what we mean by the word "consciousness". That question is also too hard, so let's take another step back. What are some of the properties of consciousness? We obviously mean something when we speak that word; it has certain connotations, so let's try to get some handle on some of the concepts that seem to be related to the concept of consciousness. There are quite a few.

Consciousness seems to be a property that some objects posess. Humans are conscious, and tables are not. Some scientists disagree even with such a basic statement, but at least we can agree that humans clearly have some strange property that tables do not seem to posess. We have feelings; we make decisions; we strive to understand ourselves. There is no evidence that tables do these things, so let's call that strange property that humans posess consciousness. That is not a definition, but it is a step towards understanding what it is we are trying to define.

Are dogs conscious? Probably, yes. There isn't much difference between a dog and a human. Their DNA is almost the same as ours, and the biggest feature dogs seem to lack is a large neocortex. Theirs is smaller. Most people would agree that dogs are conscious. What about pigeons? Probably, yes. Cockroaches? Why not? They make decisions. Even an amoeba makes a decision which direction to swim next, and those decisions are not random. So if we are to believe that amoebae are conscious, then there seems to be a connection between consciousness and the ability to make decisions, or free will. In fact, it seems that the concepts of consciousness and free will are closely related, if not identical. Maybe the definition of a conscious being is a being that has free will - a being that is able to make its own decisions. Is this a step forward, or are we simply replacing one puzzling concept by another?

Let's explore this connection, but first, consider the following question. Is there a test for consciousness? Can we observe an object and determine whether it is conscious or not? Alan Turing, considered by many to be the father of computer science, devised a test for artificial intelligence. It is a simple test - write a chat program that can talk to people, say on IRC, and if the program can fool a human into believing that it is itself human, then that program will have passed the Turing test. The problem is that some programs have already come very close to passing the Turing test. Just look at some of the winners of the Loebner prize. The test also seems to clump together intelligence and consciousness, and after a bit of thought, would you really be convinced that a machine that passes the Turing test is "like a human"?

The Turing test is a fascinating subject in itself, but it is clearly not a good test for consciousness. If consciousness is related to free will and decision making, then what about the following test, proposed by Alex Naverniouk? Create a small robotic cockroach that, to the naked eye, is indistinguishable from a real cockroach. Let a human observe its behaviour for as long as the human wishes. Then ask the human this question: "Is the cockroach making its own decisions, or is it being controlled remotely by someone else?" If the answer is uncertain, then the cockroach must be declared conscious. Note that this test is not about the presence of consciousness, but about its location. Is the cockroach controlled from within or from wihout? If it is controlled from within, then it is making its own decisions and is conscious. If not, then it is a zombie, a robot. What if we replace the cockroach with a cat and it still passes the test? Would we be more convinced that the robotic cat is conscious? What about a Mars rover? Those things are very intelligent. They make a lot of their own decisions and receive only high-level commands from the scientists on Earth. If an alien were to see a Mars rover in action, would the alien find the rover conscious?

Speaking of aliens, there is a very cool thought experiment I heard about from Dr. Steven Sevush on the Consciousness DVD's. He was using it to illustrate a different point, but the idea is useful here. Take a look at New York City from outer space. Its streets are full of people during the day; it lights up at night. There are periods of outflow when people leave on vacation and there are great gatherings at sporting events. After a tragedy like September 11, the city reacts by cleaning up and slowly healing the wound. What would an alien think after having observed New York City from space? Is the city alive? Well, most people would agree that it is not alive. But is it conscious? Does the city make decisions? Or is it the individual human inhabitants of the city who are conscious? How could the alien observer determine that? The distinction, once again, seems to be in the location of consciousness - is it within the city itself or within each of the persons? Sevush goes on to ask whether consciousness is inside a single human or inside each of the neurons in that human's brain? We will return to Dr. Sevush and his single-neuron theory of consciousness later. For now, I would like to think about the idea that relating consciousness to decision-making seems to lead us to ask the question, "Where is consciousness?" instead of, "What is consciousness?"

The last motivating thought experiment I will describe is another one of Alex Naverniouk's. Consider a card dealer in the game of Blackjack. There are strict rules that the dealer must follow (hit until 17, then stand, unless it's a "soft 17"). So is the Blackjack dealer conscious? Of course the dealer is human, so she is conscious. But what if we think about that human purely in her role as a dealer? She makes no decisions of her own - her whole game follows strict rules. A computer could do it. I would say that the dealer, purely in her capacity as a dealer and not as a human being, is unconscious.

We now come to the main point I would like to make about equating consciousness to free will or decision making. Assume for the moment that an amoeba is conscious. If that is unacceptable to you, you may replace the amoeba by the simplest possible organism that you would consider conscious. Suppose that a few centuries from now our scientific knowledge is so advanced that we can finally understand how an amoeba works. We know the function and purpose of every protein, every molecule and every atom of the amoeba. In fact, we are so advanced that we can simulate an amoeba and calculate precisely what its next action is going to be. We understand how the amoeba makes its decisions and can predict its next decision. Would that mean that the amoeba is not conscious? If we know exactly how an organism operates, does it make that organism into a robot, a mindless zombie? Once we fully understand the mechanisms responsible for making the amoeba's decisions, it seems to stop being conscious! What about that alien who is observing the Mars rover? At first, he thinks that the rover is conscious, but then he lands on Mars, examines the rover and find out that it's just a robot - it is unconscious because the alien knows exactly how the rover operates. Is consciousness a property only of organisms that we do not fully understand? If you say yes, then we clearly have a problem. That would mean that the definition of consciousness is "the ability to make unpredictable decisions," and that is a very bad definition.

A definition like that is completely useless and unproductive. It is saying that studying consciousness is pointless. As soon as we understand what it is, it seases being consciousness. It is elusive and unknowable by definition. Fortunately, there are some holes in my reasoning above. First of all, some people believe that we will never fully understand how an amoeba operates. Look at Heisenberg's uncertainty principle. It is a fundamental, testable law of physics that one is never able to know the exact posistion and momentum of an electron. It's impossible. Therefore, we will never be able to understand everything there is to know about any single atom, much less an amoeba. This is our first encounter of quantum mechanics in the context of consciousness, and it is only the beginning. We will get to other fascinating connections soon.

To summarise, if we assume that conscioiusness is the same as free will (the ability to make independent decisions), then first of all, we constantly find ourselves asking the question, "Where is consciousness located?" Once we localise consciousness to a physical body, like a human brain, or a cockroach, or an amoeba, we must immediately conclude that understanding the process in which that body makes decisions must be unknowable to us. Otherwise, our definition of consciousness makes no sense at all - we are forced to define "conscious" as "unpredictable", and that just seems wrong. We, as humans, are not conscious just because we are unpredictable. So (at least) one of our assumptions must be false. I would like to believe that eventually, the world can be understood by a human mind. The thought that some things are fundamentally incomprehensible bothers me as a scientist. Hence, I would rather believe that defining consciousness in terms of free will is not the right way to go, and we should be looking for another definition.

Friday, January 06, 2006

Part 2: Defining intelligence

Most of the following ideas come from Jeff Hawkins' book, On Intelligence. Although in the book, Hawkins seems to be confusing intelligence and consciousness in a few places, he still presents a very believable theory of what he calls "true intelligence".

It's all about the neocortex, or cortex for short. Cortex is that wrinkly outside part of the brain. First of all, the most important physiological difference between humans and chimps seems to be the size of our cortex. Sure, we also have less hair, lack a tail and aren't as good at grabbing tree branches with our feet, but the size of our cortex is what seems to be the reason why humans are smarter than chimps. Second of all, humans do not have the biggest brain of all animals, but we do have the biggest cortex, by far.

So what is the cortex made of? It is built out of billions of fatty cells called neurons. Neurons can be active or passive - they switch on and off all of the time. When a neuron is active, it sends electro-chemical signals to its neighbouring neurons across neuron-neuron connections that are called synapses. As a result of signals being sent, the synapses may get stronger or weaker, allowing for stronger or weaker signals to be sent through them. This is an extremely simplified view of a neural network in the human brain. In fact, there are other types of connections that are present between some neurons, and there are different types of neurons that perform different functions, but we will keep things simple here.

All of the neurons are arranged into six layers. That's not just a random number thrown in to make the theory look fancy; we can actually see the 6 layers through a microscope. The bottom layer has connections to our senses. Our optical nerves carry signals from the retina to the bottom layer. That is also where we receive signals from the auditory nerve and the touch, taste and smell sensors. When the bottom layer neurons receive signals, they get activated, or excited. That causes some neurons on the next layer to get excited, too. Eventually, the signals propagate to higher and higher layers. And that is how we recognize images and objects. At least that was the state of our knowledge until recently.

Here is an interesting experiment conducted by Rodrigo Quiroga and his colleagues to test an idea proposed in 1967 by a neuroscientist Jerry Lettvin. It turns out that in your brain you have a Bill Clinton neuron - a single neuron that gets excited whenever you see the face of Bill Clinton, or hear the voice of Bill Clinton, or read the words "Bill Clinton". Well, actually there are several such neurons, duplicated just to be safe. That's no joke. Such neurons that are responsible for particular concepts are called "grandmother cells" or "gnostic" units. This suggests that when we see an image of Bill Clinton, somehow the cells in the retinas of our eyes send signals down the optical nerve, and those signals get received by the bottom layer of the cortical hierarchy; then, the signals propagate to higher layers until in the top layer the Bill Clinton neuron gets excited, and we recognize the face.

That is the simple view held by many neuroscientists. In fact, things seem to be a lot more interesting. Our eyes never take just one look at a face. Instead, they always rapidly jump from one facial feature to the other - left eye, right eye, nose, left eye, mouth, right eye, etc. What our brain is getting is a sequence of snapshots of small features of a person's face. In turn, the brain is telling the eyes what to look at next. This happens on every layer - information from the censors flows up the hierarchy, and the brain's commands, or signals, flow down to the muscles.

Now here is the cool part. The signals that flow down the hierarchy are predictions that our brain makes of the future. Here is what happens when we see a face. Our eyes catch a glimpse of a nose. The brain tells the eyes, "Look down a little bit, you should see a mouth." The eyes look below and see the mouth. The brain says, "Now look up and to the left, and you should see the right cheek". Our eyes jump to the right cheek. At this point, the brain starts recognizing the face of Bill Clinton and says, "Now look at the right eye; it should look like Bill Clinton's right eye." This process continues, as the brain gets more and more certain that we are indeed looking at the face of Bill Clinton. At every moment, each neuron is receiving sensory inputs from below and predictions from above and matching the two together.

It gets better. Ask yourself, "What is learning?" When do we learn new things? The answer is: precisely when our predictions do not match what we are percieving. Suppose that you are talking to somebody you have never seen before. Your eyes are trying to recognize the person's face, but where you have been expecting to see a chin, you notice a beard instead. To your facial recognition neurons, this is unexpected, so they get excited and start sending signals to the layer above. Eventually, these signals cause you to recognize that there is a relationship between the name of the person that you are talking to and the notion of a beard. From now on, whenever the neuron representing that person in your brain gets excited, the "beard neuron" will also get excited. In fact, if you are ever asked to describe that person, you might start by saying something like, "A tall guy with a beard." I'm speculating here and hiding many details, but the general idea makes sense.

There are fascinating questions about the way in which we build new memories. An area of the brain called the hippocampus seems to play a major role in it. After damaging their hippocampus, people lose the ability to remember new events (see Memento), although their older memories seem unaffected. It is likely that the only reason we require sleep is to transfer new memories acquired during the day to more permanent memory and free up space in the hippocampus for new information. I know for a fact that when I am deprived of sleep, my short-term memory suffers; I start forgetting appointments and losing my keys.

In short, the human neocortex is an extremely powerful tool that serves two purposes - (1) translating enormous amounts of information received by our senses into a language of abstract concepts and (2) translating commands given by the brain from the languages of abstractions to sequences of nerve signals that go off to the various muscles that control the way in which we affect the world around us. That is intelligence - the fact that we are able to reason about and interact with the world in terms of high-level abstract concepts. Jeff Hawkins claims that that is all we are, and that soon we will be able to build computers that simulate the functions of the neocortex and behave intelligently - like humans do.

The book left me with the feeling that I should sit down and start programming somthing right now! However, after thinking about it a little bit, I found that there are two huge holes in Hawkins' theory. Alright, I can build a six-layer network of a million neurons, have them get excited and send signals to each other. But wait; what does a single neuron do? There is a lot of evidence that all neurons are pretty much the same in terms of what they do, but what is it... that they do? They learn to recognize patters of signals. How? Does one neuron have a very simple function or a very complicated one? That is the first problem you run into when you ambitiously open a text editor to write some brain simulating code.

The second problem is the transition between perception and prediction. Alright, I can organize a hierarchy of neurons that will pass messages up and down. On the bottom, I will connect a bunch of sensors - vision, hearing, etc. Signals will propagate up to the top layer. But what do I connect at the top? Who is it that little demon that sits there, observes the Bill Clinton, grandmother and beard neurons light up and makes a decision which muscle to move? That's consciousness! I am calling it that for lack of a better term. When you are talking to somebody, a lot of thoughts rush through your mind, but somehow out of all that mess you build a sentense and speak it. We know how from the sounds that you hear, your brain builds a complicated concept of what the speaker is saying - that's the cortex. We know how your ideas get transformed into hundreds of complicated nerve signals that move your lips and tongue to produce speech - that's the cortex, too. But what happens between the time you understand what the other person has said and the time you have decided on an appropriate reply? Who makes that decision? Is there a decision being made? This is precisely the "hard problem" of consciousness again. In a sense, the cortex is no different from the hand - it is an organ that humans have evolved to ease the task of interacting with the world. The cortex is the organ of intelligence.

Most scientists believe that these two problems are actually the same problem. The place where the little demon sits is inside the neurons. But that is where the question of intelligence ends and the question of consciousness begins, and if you thought the cortex was weird, from now on things get really hairy.

Part 1: The Basiscs, or lack thereof

Before we can have a sane discussion about "smart computers," we need to define a few things. Unfortunately, that is where most of the troubles begin. How do you define "intelligence"? It gets worse - how do you tell whether something is intelligent? Is a dolphin intelligent? How about a dog? A crab? Most scientists have no idea how to define "intelligence", "consciousness", "awareness", "thought", "mind", "soul", "free will" or anything that has to do with that "stuff" that seems to make humans fundamentally different from trees.

On the bright side, we seem to be settling in on a few conventions, so things are not that grim. The first important idea that is not at all obvious is that there is a fundamental difference between intelligence and consciousness. Several speakers on the DVD set agree on this. Here is the argument they give. Intelligence is not an absolute quantity; it is relative. Instead of calling objects either "intelligent" or "unintelligent", we should say that humans are more intelligent than dogs, and monkeys are more intelligent than birds. Consciousness, on the other hand, seems to be a binary property - humans are conscious and tables are not. (Although there is disagreement on that point, too.)

But what about intelligent computers? The argument is that many computers are intelligent already. Take, for example, Deep Blue - a computer that plays on par with the best human chess players in the world. In the world of chess, Deep Blue makes intelligent decisions. If intelligent is the opposite of stupid, then it is hard to argue agains that. This is where most people say, "Wait. That's not what we are talking about. Computers play chess using brute force calculations. There is nothing intelligent about that. It's just memorization." But how could you tell? If the only thing you could see was the chessboard of the match between Deep Blue and Garry Kasparov, could you say right away who was playing which side? The point is that Deep Blue is making intelligent decisions.

Of course, there is something fundamentally different about the way Kasparov and Deep Blue think. That is the difference between intelligence and consciousness. The argument is that we should stop looking for Artificial Intelligence (AI) and start looking for Artificial Consciousness. AI is already here, and there is nothing special about it. It is clear that Kasparov is conscious, and Deep Blue is not. Now if intelligence is the ability to make intelligent decisions, then what is consciousness? Humans are conscious. Dogs are conscious. Even bacteria seem to be conscious! If you look at some bacteria in the microscope, they wiggle. They move through water in ways that seem random. Some bacteria have the ability to swim towards salty water. If you have a water tank that has one side where the water is more salty, these bacteria will find a way to get there. The bacteria are making a decision. This decision has been programmed into their DNA by evolution. Are these bacteria intelligent? Probably not. Are they conscious? Probably yes. Are computers conscious? Almost certainly not.

So what is consciousness? That is probably the most difficult question. Scientists call it the "hard problem", a term coined by David Chalmers. It turns out that defining intelligence is much easier than defining consciousness.

Here is my personal view on the situation. This view is likely to change. I think that "life", "consciousness" and "intelligence" are all different properties. Intelligence is the ability to make decisions based on sensory inputs and past experiences, an ability to learn. In that sense, computers are intelligent. Life is that which is studied by biology. Several definitions of life have been proposed over the centuries, and they are basically right. Things that are alive grow, reproduce and die. Life is what distinguishes a tree from a rock. Consciousness is what distinguishes animals from plants. Bacteria are conscious. Flowers are not.

Many scientists disagree with this view. There also seem to be gray areas on the boundary between alive and dead. Crystals grow and reduce entropy; are they alive? Worker bees and infertile people do not reproduce; are they alive? Virii do not grow; are they alive? What about the possibility of silicon-based life forms? The bondary between plants and animals is not very clear either. What about mushrooms, or flowers that eat flies, or virii again? Maybe our current definition of life is completely wrong. Finding new life forms on other planets would certainly help us clarify things and zoom in on the properties that are unique to life only. There is also the possibility that it is all an illusion, and there is really no fundamental difference between a tree and a rock, but that argument sounds like giving up to me. There is clearly life on Earth. And there is clearly no life on the Moon. What's up with that?

Let's leave the concept of life to another discussion and move on to something that should be more interesting to humans. We, as humans, are not just alive. We are also conscious and intelligent. Before I talk about the "hard problem" of defining consciousness, let's get the simpler concept out of the way first - intelligence.


What is this about? After reading Jeff Hawkins' On Intelligence and watching a series of DVD's entitled "Consciousness", I discovered that I have a lot of questions and ideas, so I decided to write them all down in an effort to make some sense of it all. As for the title of this blog, every other title was taken. Well, not quite. The reason I got interested in consciousness, intelligence and all of this wishy-washy, voodoo stuff was because I wanted to know whether it was possible to code an intelligent computer program. As it turns out, the answer is yes, although it would turn out quite unsatisfactory. In fact, people have been writing intelligent programs for quite some time, and it turns out that what we should really be looking for is a conscious computer program.

But I'm getting ahead of myself. This is just an introduction, and as is customary, let me introduce myself. My name is igor and I am a Ph.D. student in Computer Science at the University of Toronto. I am a pretty good computer programmer, and I don't believe in Artificial Intelligence, as in Hal, Data or the Three Laws of Robotics. At least I started out that way before I listened to Stuart Hameroff and his friends (and enemies). Now I'm just confused.