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July 12, 2017
Donald Hoffman - Our Perceptions of an Independent Reality must be Illusions
Donald D. Hoffman - The Nature of Our Consciousness and the Reality
Prof. Donald D. Hoffman ( ddhoff@uci.edu ) : Department of Cognitive Sciences, University of California Irvine CA 92697 USA www.cogsci.uci.edu/~ddhoff | Amazon Page
Lecture : Consciousness and The Interface Theory of Perception
Despite substantial efforts by many researchers, we still have no scientific theory of how brain activity can create, or be, conscious experience. This is troubling, since we have a large body of correlations between brain activity and consciousness, correlations normally assumed to entail that brain activity creates conscious experience. Here I explore a solution to the mind-body problem that starts with the converse assumption: these correlations arise because consciousness creates brain activity, and indeed creates all objects and properties of the physical world.
To this end, I develop two theses. The interface theory of perception states that perceptual experiences do not match or approximate properties of the objective world, but instead provide a simplified, species-specific, user interface to that world. Conscious realism states that the objective world consists of conscious agents and their experiences; these can be mathematically modeled and empirically explored in the normal scientific manner.
In support of the interface theory of perception, I present Monte Carlo simulations of evolutionary games in which perceptual strategies that see the truth compete with perceptual strategies that do not see the truth but are instead tuned to fitness. The result is that natural selection drives true perceptions to swift extinction. Our perceptions have evolved to guide adaptive behaviors, not to report the truth.
In support of conscious realism, I present a dynamical theory of consciousness in which the observer and the observed have precisely the same mathematical structure, i.e., in which there is a mathematically precise nondualism. I then derive the quantum wave function of the free particle from the asymptotic behavior of the conscious dynamics. This is a step toward solving the mind-body problem from the assumption that consciousness, not physics, is fundamental.
"Our perceptions of space-time and objects are a species-specific adaptation, not an insight into objective reality. In consequence, I propose a formal theory of consciousness —the theory of 'conscious agents'— that takes consciousness to be fundamental, rather than derivative from objects in space-time.
I use the theory of conscious agents to solve the combination problem of consciousness, both for the combination of subjects and of experiences. I show that entanglement follows as a consequence of the combination of conscious subjects. I then discuss the relationship of these findings to the account of entanglement given by quantum-Bayesian interpretations of quantum theory."
The cognitive scientist Donald Hoffman uses evolutionary game theory to show that our perceptions of an independent reality must be illusions.
"...Evolution has shaped us with perceptions that allow us to survive. They guide adaptive behaviors. But part of that involves hiding from us the stuff we don’t need to know. And that’s pretty much all of reality, whatever reality might be. If you had to spend all that time figuring it out, the tiger would eat you...."
As we go about our daily lives, we tend to assume that our perceptions —sights, sounds, textures, tastes— are an accurate portrayal of the real world. Sure, when we stop and think about it —or when we find ourselves fooled by a perceptual illusion— we realize with a jolt that what we perceive is never the world directly, but rather our brain’s best guess at what that world is like, a kind of internal simulation of an external reality. Still, we bank on the fact that our simulation is a reasonably decent one. If it wasn’t, wouldn’t evolution have weeded us out by now? The true reality might be forever beyond our reach, but surely our senses give us at least an inkling of what it’s really like.
Not so, says Donald D. Hoffman, a professor of cognitive science at the University of California, Irvine. Hoffman has spent the past three decades studying perception, artificial intelligence, evolutionary game theory and the brain, and his conclusion is a dramatic one: The world presented to us by our perceptions is nothing like reality. What’s more, he says, we have evolution itself to thank for this magnificent illusion, as it maximizes evolutionary fitness by driving truth to extinction.
Getting at questions about the nature of reality, and disentangling the observer from the observed, is an endeavor that straddles the boundaries of neuroscience and fundamental physics. On one side you’ll find researchers scratching their chins raw trying to understand how a three-pound lump of gray matter obeying nothing more than the ordinary laws of physics can give rise to first-person conscious experience. This is the aptly named "hard problem."
On the other side are quantum physicists, marveling at the strange fact that quantum systems don’t seem to be definite objects localized in space until we come along to observe them — whether we are conscious humans or inanimate measuring devices. Experiment after experiment has shown — defying common sense — that if we assume that the particles that make up ordinary objects have an objective, observer-independent existence, we get the wrong answers. The central lesson of quantum physics is clear: There are no public objects sitting out there in some preexisting space. As the physicist John Wheeler put it, “Useful as it is under ordinary circumstances to say that the world exists ‘out there’ independent of us, that view can no longer be upheld.”
So while neuroscientists struggle to understand how there can be such a thing as a first-person reality, quantum physicists have to grapple with the mystery of how there can be anything but a first-person reality. In short, all roads lead back to the observer. And that’s where you can find Hoffman — straddling the boundaries, attempting a mathematical model of the observer, trying to get at the reality behind the illusion. Quanta Magazine caught up with him to find out more. An edited and condensed version of the conversation follows.
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QUANTA MAGAZINE: People often use Darwinian evolution as an argument that our perceptions accurately reflect reality. They say, “Obviously we must be latching onto reality in some way because otherwise we would have been wiped out a long time ago. If I think I’m seeing a palm tree but it’s really a tiger, I’m in trouble.”
DONALD HOFFMAN: Right. The classic argument is that those of our ancestors who saw more accurately had a competitive advantage over those who saw less accurately and thus were more likely to pass on their genes that coded for those more accurate perceptions, so after thousands of generations we can be quite confident that we’re the offspring of those who saw accurately, and so we see accurately. That sounds very plausible. But I think it is utterly false. It misunderstands the fundamental fact about evolution, which is that it’s about fitness functions — mathematical functions that describe how well a given strategy achieves the goals of survival and reproduction. The mathematical physicist Chetan Prakash proved a theorem that I devised that says: According to evolution by natural selection, an organism that sees reality as it is will never be more fit than an organism of equal complexity that sees none of reality but is just tuned to fitness. Never.
You’ve done computer simulations to show this. Can you give an example?
Suppose in reality there’s a resource, like water, and you can quantify how much of it there is in an objective order — very little water, medium amount of water, a lot of water. Now suppose your fitness function is linear, so a little water gives you a little fitness, medium water gives you medium fitness, and lots of water gives you lots of fitness — in that case, the organism that sees the truth about the water in the world can win, but only because the fitness function happens to align with the true structure in reality. Generically, in the real world, that will never be the case. Something much more natural is a bell curve — say, too little water you die of thirst, but too much water you drown, and only somewhere in between is good for survival. Now the fitness function doesn’t match the structure in the real world. And that’s enough to send truth to extinction. For example, an organism tuned to fitness might see small and large quantities of some resource as, say, red, to indicate low fitness, whereas they might see intermediate quantities as green, to indicate high fitness. Its perceptions will be tuned to fitness, but not to truth. It won’t see any distinction between small and large — it only sees red — even though such a distinction exists in reality.
But how can seeing a false reality be beneficial to an organism’s survival?
There’s a metaphor that’s only been available to us in the past 30 or 40 years, and that’s the desktop interface. Suppose there’s a blue rectangular icon on the lower right corner of your computer’s desktop — does that mean that the file itself is blue and rectangular and lives in the lower right corner of your computer? Of course not. But those are the only things that can be asserted about anything on the desktop — it has color, position and shape. Those are the only categories available to you, and yet none of them are true about the file itself or anything in the computer. They couldn’t possibly be true. That’s an interesting thing. You could not form a true description of the innards of the computer if your entire view of reality was confined to the desktop. And yet the desktop is useful. That blue rectangular icon guides my behavior, and it hides a complex reality that I don’t need to know. That’s the key idea. Evolution has shaped us with perceptions that allow us to survive. They guide adaptive behaviors. But part of that involves hiding from us the stuff we don’t need to know. And that’s pretty much all of reality, whatever reality might be. If you had to spend all that time figuring it out, the tiger would eat you.
So everything we see is one big illusion?
We’ve been shaped to have perceptions that keep us alive, so we have to take them seriously. If I see something that I think of as a snake, I don’t pick it up. If I see a train, I don’t step in front of it. I’ve evolved these symbols to keep me alive, so I have to take them seriously. But it’s a logical flaw to think that if we have to take it seriously, we also have to take it literally.
If snakes aren’t snakes and trains aren’t trains, what are they?
Snakes and trains, like the particles of physics, have no objective, observer-independent features. The snake I see is a description created by my sensory system to inform me of the fitness consequences of my actions. Evolution shapes acceptable solutions, not optimal ones. A snake is an acceptable solution to the problem of telling me how to act in a situation. My snakes and trains are my mental representations; your snakes and trains are your mental representations.
How did you first become interested in these ideas?
As a teenager, I was very interested in the question “Are we machines?” My reading of the science suggested that we are. But my dad was a minister, and at church they were saying we’re not. So I decided I needed to figure it out for myself. It’s sort of an important personal question — if I’m a machine, I would like to find that out! And if I’m not, I’d like to know, what is that special magic beyond the machine? So eventually in the 1980s I went to the artificial intelligence lab at MIT and worked on machine perception. The field of vision research was enjoying a newfound success in developing mathematical models for specific visual abilities. I noticed that they seemed to share a common mathematical structure, so I thought it might be possible to write down a formal structure for observation that encompassed all of them, perhaps all possible modes of observation. I was inspired in part by Alan Turing. When he invented the Turing machine, he was trying to come up with a notion of computation, and instead of putting bells and whistles on it, he said, Let’s get the simplest, most pared down mathematical description that could possibly work. And that simple formalism is the foundation for the science of computation. So I wondered, could I provide a similarly simple formal foundation for the science of observation?
A mathematical model of consciousness.
That’s right. My intuition was, there are conscious experiences. I have pains, tastes, smells, all my sensory experiences, moods, emotions and so forth. So I’m just going to say: One part of this consciousness structure is a set of all possible experiences. When I’m having an experience, based on that experience I may want to change what I’m doing. So I need to have a collection of possible actions I can take and a decision strategy that, given my experiences, allows me to change how I’m acting. That’s the basic idea of the whole thing. I have a space X of experiences, a space G of actions, and an algorithm D that lets me choose a new action given my experiences. Then I posited a W for a world, which is also a probability space. Somehow the world affects my perceptions, so there’s a perception map P from the world to my experiences, and when I act, I change the world, so there’s a map A from the space of actions to the world. That’s the entire structure. Six elements. The claim is: This is the structure of consciousness. I put that out there so people have something to shoot at.
But if there’s a W, are you saying there is an external world?
Here’s the striking thing about that. I can pull the W out of the model and stick a conscious agent in its place and get a circuit of conscious agents. In fact, you can have whole networks of arbitrary complexity. And that’s the world.
I call it conscious realism: Objective reality is just conscious agents, just points of view. Interestingly, I can take two conscious agents and have them interact, and the mathematical structure of that interaction also satisfies the definition of a conscious agent. This mathematics is telling me something. I can take two minds, and they can generate a new, unified single mind. Here’s a concrete example. We have two hemispheres in our brain. But when you do a split-brain operation, a complete transection of the corpus callosum, you get clear evidence of two separate consciousnesses. Before that slicing happened, it seemed there was a single unified consciousness. So it’s not implausible that there is a single conscious agent. And yet it’s also the case that there are two conscious agents there, and you can see that when they’re split. I didn’t expect that, the mathematics forced me to recognize this. It suggests that I can take separate observers, put them together and create new observers, and keep doing this ad infinitum. It’s conscious agents all the way down.
If it’s conscious agents all the way down, all first-person points of view, what happens to science? Science has always been a third-person description of the world.
The idea that what we’re doing is measuring publicly accessible objects, the idea that objectivity results from the fact that you and I can measure the same object in the exact same situation and get the same results — it’s very clear from quantum mechanics that that idea has to go. Physics tells us that there are no public physical objects. So what’s going on? Here’s how I think about it. I can talk to you about my headache and believe that I am communicating effectively with you, because you’ve had your own headaches. The same thing is true as apples and the moon and the sun and the universe. Just like you have your own headache, you have your own moon. But I assume it’s relevantly similar to mine. That’s an assumption that could be false, but that’s the source of my communication, and that’s the best we can do in terms of public physical objects and objective science.
It doesn’t seem like many people in neuroscience or philosophy of mind are thinking about fundamental physics. Do you think that’s been a stumbling block for those trying to understand consciousness?
I think it has been. Not only are they ignoring the progress in fundamental physics, they are often explicit about it. They’ll say openly that quantum physics is not relevant to the aspects of brain function that are causally involved in consciousness. They are certain that it’s got to be classical properties of neural activity, which exist independent of any observers — spiking rates, connection strengths at synapses, perhaps dynamical properties as well. These are all very classical notions under Newtonian physics, where time is absolute and objects exist absolutely. And then [neuroscientists] are mystified as to why they don’t make progress. They don’t avail themselves of the incredible insights and breakthroughs that physics has made. Those insights are out there for us to use, and yet my field says, “We’ll stick with Newton, thank you. We’ll stay 300 years behind in our physics.”
I suspect they’re reacting to things like Roger Penrose and Stuart Hameroff’s model, where you still have a physical brain, it’s still sitting in space, but supposedly it’s performing some quantum feat. In contrast, you’re saying, “Look, quantum mechanics is telling us that we have to question the very notions of ‘physical things’ sitting in ‘space.’”
I think that’s absolutely true. The neuroscientists are saying, “We don’t need to invoke those kind of quantum processes, we don’t need quantum wave functions collapsing inside neurons, we can just use classical physics to describe processes in the brain.” I’m emphasizing the larger lesson of quantum mechanics: Neurons, brains, space … these are just symbols we use, they’re not real. It’s not that there’s a classical brain that does some quantum magic. It’s that there’s no brain! Quantum mechanics says that classical objects — including brains — don’t exist. So this is a far more radical claim about the nature of reality and does not involve the brain pulling off some tricky quantum computation. So even Penrose hasn’t taken it far enough. But most of us, you know, we’re born realists. We’re born physicalists. This is a really, really hard one to let go of.
To return to the question you started with as a teenager, are we machines?
The formal theory of conscious agents I’ve been developing is computationally universal — in that sense, it’s a machine theory. And it’s because the theory is computationally universal that I can get all of cognitive science and neural networks back out of it. Nevertheless, for now I don’t think we are machines — in part because I distinguish between the mathematical representation and the thing being represented. As a conscious realist, I am postulating conscious experiences as ontological primitives, the most basic ingredients of the world. I’m claiming that experiences are the real coin of the realm. The experiences of everyday life — my real feeling of a headache, my real taste of chocolate — that really is the ultimate nature of reality. ------------
I appreciate everyone’s comments, and I’m hoping to clear up a few misunderstandings. First, I respect the skepticism people have shown here. Nine times out of ten, when you see “consciousness” and “quantum” in the same article, you are reading crackpot, pseudoscience nonsense, so it’s important to be cautious. I am too. But having spoken with Hoffman at great length (this Q&A, of course, being a piece of a much larger conversation), I can assure you that he is a serious, thoughtful, rigorous scientist. He could always be wrong, of course, but he’s making subtle, important points that unfortunately have been lost in the discussion.
Hoffman is not claiming anything like “quantum wavefunctions are collapsed by consciousness” or “consciousness can be explained by some kind of quantum voodoo.” The two were not being invoked to explain one another, or to conflate quantum weirdness with cognitive mysteries. Indeed, Hoffman emphasizes that his model of consciousness is computationally universal – which is to say, there’s no magic to it. It could be implemented by man or machine; there’s nothing about the brain that fundamentally sets it apart from any other physical system. Hoffman also distinguishes his view from something like the Penrose-Hameroff model, where you have quantum coherence within neurons. As one commenter said, the brain is warm and wet. It seems impossible to keep decoherence at bay. Even if it weren’t, it’s unclear (to me, anyway) how quantum superpositions could possibly help to explain consciousness. It doesn’t matter – none of this is what Hoffman is saying. As he put it, the brain is not “doing some quantum magic.” At the scale of neurons in an environment like the brain, quantum effects are virtually irrelevant. I think we can all agree.
On the quantum side, Hoffman is not endorsing a Copenhagen-esque view. He does not think that consciousness magically reaches out of the skull and into the world to collapse quantum wavefunctions. (As it happens, he’s partial to the QBist interpretation.) That is to say: quantum mechanics does not require conscious observers. (Ok, maybe if you consider the wavefunction to be epistemic from the start, it does by definition. But that’s a subtle point, and it doesn’t suffer the inexplicable dualism of Copenhagen.) As for me, when I spoke of “observer-dependence” I did not mean that an observer is something with consciousness. It could be a reference frame, a Geiger counter, dust, whatever. “Observer” is shorthand for a perspective or point of view. (In relativity, an “observer” might be a spacetime coordinate system. In quantum mechanics, it’s something like an algebra of quantum operators or a Boolean lattice. What matters is that it’s some limited, bounded perspective. Whether that perspective is “conscious”…well I doubt that’s even a well-posed question. Either way, it’s irrelevant.)
Ok, so why are consciousness and quantum mechanics appearing in a single conversation? To emphasize that they are two sides of a coin when it comes to the fundamental nature of reality. (If you believe science shouldn’t deal with the nature of reality, you might want to stop reading here. For me, this is exactly where we need science the most, lest we get lost in bad metaphysics.) Look at the “hard problem”. It’s usually phrased something like this: “How, in a world made of ordinary matter, can anything like consciousness or first-person experience ever arise?” Matter is posed as the known element, consciousness as the mystery. The “ordinary matter” assumed is a kind of folk ontology derived from classical physics, and not the actual ontology given (or allowed) by fundamental physics. “How, in an objective universe, can something like subjectivity exist?” The question de facto assumes that there is an objective universe. But that’s not a claim that can be made by neuroscience or philosophy of mind. That’s physics.
So what does physics actually say about it? Well, it says something super subtle that one would be an idiot to try to unpack in the comments section…so here I go. People talk about quantum mechanics being mysterious. But really, it only becomes mysterious when you try to apply it to more than one observer simultaneously. (Observer = reference frame; see above.) This is something every interpretation of quantum mechanics has to contend with. In fact, it’s why there are different interpretations to begin with. If you try to assume that particles have definite values or locations in spacetime and then run an experiment (like EPR) you will get the wrong answers. Those values and locations only exist relative to a given measurement. What’s the electron doing when it’s not interacting with anything? It’s a meaningless question because there can be no interaction-independent answer. The common sense notion that there are objects with features everyone would agree on that are sitting in some objective space shared by multiple observers is simply not upheld by quantum mechanics. (Yes, yes, of course decoherence can save appearances, it can hide this fact, it does it really well, hence our common sense notions! But the whole point is that we’re not interested in mere appearances, we’re trying to get to the nature of things.) So what is the world, according to quantum mechanics? It’s a bunch of “first-person” points of view, full stop.
One might protest: I can make a measurement and then you can make a measurement and we can compare notes, find that we agree and in doing so glimpse an observer-independent reality. But quantum mechanics doesn’t allow you to do that. There’s no non-quantum, God’s eye point of view from which one can compare. You can only compare points of view from within a point of view. In other words, the comparison itself is a quantum measurement. It’s quantum all the way up. (Does this veer toward solipsism? Kinda. But with science, you get what you get. And it’s not a make-up-your-own-reality situation, there are physical laws that impose strict consistency conditions within a point of view. And there may be ways to link them into something less solipsistic – but no one’s quite done it yet. Things like the black hole firewall paradox frustrate the efforts. That’s for another day, another comment.)
Back to Hoffman. He’s saying, look, cognitive scientists are scrambling to figure out how our first-person perspectives relate to the actual objects that are sitting out there in the external space that we all share and meanwhile, physicists are saying that the premise is flawed from the start. (The physicist Tom Banks put it this way: “Space arises from the quantum mechanical relations between different observers.” That is, space (a the third-person objective point of view) is derived from the relations among first-person perspectives—not the other way around. Or take Carlo Rovelli: “A universal observer-independent description of the state of affairs of the world does not exist.”) So when Hoffman’s evolutionary game theory simulations turned up a model of perception that ran counter to our common sense metaphysics, he realized, hey, quantum mechanics already ruled that out that metaphysics anyway. Does any of this matter at the scale of your everyday life? Does it discount everything we’ve learned about neurons and brains and objects and perception? No. Don’t pick up snakes, don’t step in front of trains. But should we discount a model of cognition that runs counter to folk physics, reject some deep truth because it defies experience at the scales of our everyday life? No. Carlo Rovelli wrote, “My effort is not to modify quantum mechanics to make it consistent with my view of the world, but to modify my view of the world to make it consistent with quantum mechanics.” That is what Hoffman is trying to do here.
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