What Is It Like to Be a Brain Simulation? Eray Özkural February 5, 2014 Abstract We frame the question of what kind of subjective experience a brain simulation would have in contrast to a biological brain. We discuss the brain prosthesis thought experiment. Then, we identify finer questions relating to the original inquiry, and set out to answer them moving forward from both a general physicalist perspective, and pan-experientialism. We propose that the brain simulation is likely to have subjective experience, however, it may differ significantly from human experience. Additionally, we discuss the relevance of quantum properties, digital physics, theory of relativity, and information theory to the question. 1 Introduction The nature of experience is one of those deep philosophical questions which philosophers and scientists alike have not been able to reach a consensus on. In this article, I review a computational variant of a basic question of subjectivity. In his classical article "What is it like to be a bat?", Thomas Nagel investigates whether we can give a satisfactory answer to the question in the title of his article, and due to what he thinks to be fundamental barriers, concludes that it is not something we humans can know Nagel [1974]. We can intuitively agree that although the bat's brain must have many similarities to a human's, since both species are mammalian, the bat brain contains a sensory modality quite unlike any which we possess. By induction, we can guess that perhaps the difference between sonar perception and our visual experience could be as much as the difference between our visual and auditory perception. Yet, in some sense sonar is both visual and auditory, and still it is neither visual nor auditory. It is more similar to vision, because it helps build a model of the scene around us, however, instead of stereoscopic vision, the bat sonar can make accurate 3-D models of the environment from a particular point of view, in contrast with normal vision that is said to have "2-1/2D vision". Therefore, it is unlike anything that humans experience, and perhaps our wildest imaginations of bat sonar experience are doomed to fall short of the real thing. Namely, because it is difficult for us to understand the experience of a detailed and perhaps rapidly updated 3-D scene that does not contain optical experience as there is no 2-D image data from eyes to be interpreted. This would likely require specialized neural circuitry. And despite what Nagel has in mind, it seems theoretically possible to "download" bat sonar circuitry into a human brain (by growing the required neural module according to a given specification, connected to sonar equipment 1 implanted in the body) so that the human can experience the same sensory modality. In this problem, armchair philosophy alone may not be sufficient. The barrier to knowing what it is like to be a bat is, thus, mostly a technological barrier, rather than a conceptual or fundamental barrier. Though, ultimately, it may be argued that we cannot expect one to know exactly what a bat experiences, short of being one. In the best case, we would know what a bat experience is like, as the human brain could be augmented with a reconstruction of the perceptual machinery. That being the case, we may also consider what a brain simulation, or an "upload" as affectionately called in science fiction literature, would experience, or whether it would experience anything at all, as brain simulation is a primary research goal on which computational neuroscientists have already made progress, e.g., Izhikevich and Edelman [2008b]. The question that I pose is harder because the so-called upload usually does not run on a biological nervous system, and it is easier because the processing is the simulation of a human brain (and not something else). Answering this question is important, because presumably the (subjective) experience, the raw sensations and feelings of a functional human brain, are very personal and valuable to human beings. We would like to know, if there is a substantial loss or difference in the quality of experience for our minds' digital progeny. A recent survey of large-scale brain simulation projects may be found in Garis et al. [2010]. 2 Brain prosthesis thought experiment The question is also very similar to the brain prosthesis thought experiment, in which biological neurons of a brain are gradually replaced by functionally equivalent (same input/output behavior) synthetic (electronic) neurons Moravec [1990]. In that thought experiment, we ponder how the subjective experience of the brain would change. Although there are challenging problems such as interfacing smoothly with existing neural tissue, it is a scientifically plausible thought experiment, also discussed at some length in [Russell and Norvig, 1995, Section 26.4]. Moravec suggests that nothing would change with respect to conscious experience in his book. Marvin Minsky has written similarly while discussing whether machines can be conscious Minsky [1991]. He produces an argument similar to Wittgenstein's "beetle-in-a-box" thought experiment: since a brain simulation is supposed to be functionally equivalent, its utterances would be complete, and the brain simulation would know consciousness and claim to be conscious; why should we think that the simulation is lying deliberately? This is a quite convincing argument, however, it only neglects to mention that a form of physical epiphenomenalism could be true (in that experiential states may mirror electrical signals, yet they may be distinct physically). Contrariwise, John R. Searle maintains that the experience would gradually vanish in his book titled "The Rediscovery of the Mind" Searle [1992]. The reasoning of Minsky and Moravec seems to be that it is sufficient for the entire neural computation to be equivalent at the level of electrical signaling (as the synthetic neurons are electronic), while they seem to disregard other brain states. While for Searle, experience can only exist in "the right stuff", which he seems to be taking as biological substrate, although one cannot be certain Searle [1980]. We will revisit this division of views soon enough, for we shall identify yet another 2 possibility. 3 Naturalist theories of experience An often underrated theory of experience is panpsychism, the view that all matter has mental properties. It is falsely believed by some that panpsychism is necessarily incompatible with physicalism. However, this is far from a settled controversy. Strawson has recently claimed that physicalism entails panpsychism Strawson [2006]. We must also mention the view of pan-experientialism: that experience resides in every physical system, however, not everything is a conscious mind, for that requires cognition in addition. Panpsychism is also proposed as an admissible philosophical interpretation of human-like AI experience in Goertzel [2011]. Why is this point of view (panpsychism) significant? The evidence from psychedelic drugs and anesthesia imply that changing the brain chemistry also modulates experience. If the experience changes, what can this be attributed to? Does the basic computation change, or are chemical interactions actually part of human experience? It seems that answering that sort of question is critical to answering the question posed in this article. However, it first starts with accepting that it is natural, like a star, or a waterfall. Only then can we begin to ask questions with more distinctive power. Over the years, I have observed that neuroscientists were often too shy to ask these questions, as if these questions were dogma. Although no neuroscientist would admit to such a thing, it makes one doubt if religious or superstitious presuppositions may have a role in the apparent reluctance of neuroscientists to investigate this fundamental question in a rigorous way. One particular study may shed light on the question Schneidman et al. [2001] which claims that the neural code forms the basis of experience, therefore changes in neural code (i.e., spike train, a spike train is the sequence of electrical signals that travel down an axon), change experience. That's a very particular claim, that can be perhaps one day proven in experiment. However, at the present it seems like a hypothesis that we can work with, without necessarily accepting it. That is to say, we are going to analyze this matter in the framework of naturalism, without ever resorting to skyhooks. We can consider a hypothesis as the aforementioned one, however, we will try to distinguish finely between what we do know and what is hypothetical. Following this methodology, and a bit of common sense, I think we can derive some scientifically plausible speculations, following the terminology of Carl Sagan. 4 The debate Let us now frame the debate more thoroughly, given our small excursion to the origin of the thought experiment. On one side, AI researchers like Minsky and Moravec seem to think that simulating a brain will just work, and experience will be unchanged relative to the original brain. On the other side, skeptics like Searle and Penrose, try everything to deny "consciousness" to poor machinekind. Although both Searle and Penrose are purportedly physicalists, they do not refrain from seeking almost magical events to explain experience. 3 However, it is not likely that word play will aid us much. We need to have a good scientific theory of when and how experience occurs. The best theory will have to be induced from experimental neuroscience and related facts. What is the most basic criterion for assessing whether the theory of experience is scientifically sound? No doubt, it comes down to rejecting each and any kind of supernatural/superstitious explanation and approach this matter the same way as we are investigating problems in molecular biology, that the experience is ultimately made up of physical resources and interactions, and there is nothing else to it; this is a view also held by Minsky as he likens mysticism regarding consciousness to vitalism Minsky [1991]. In philosophy, this approach to mind is called physicalism. A popular statement of physicalism is token physicalism: every mental state x is identical to a physical state y. That is a general hypothesis that neuroscientists already accept, because presumably, when the neuroscientist introduces a change to the brain, he would like to see a corresponding change in the mental state. One may think of cybernetic eye implants and transcranial magnetic stimulation and confirm that this holds in practice, and that the hypothesis need not be questioned, for one would find it very difficult to find counter-examples. 5 Asking the question in the right way We have discussed every basic concept to frame the question in a way akin to analysis. Mental states are physical states. The brain states in a human constitute its subjective experience. The question is whether a particular whole brain simulation, will have experience, and if it does, how similar this experience is to the experience of a human being. If the proponents of pan-experientialism are right, then this is nothing special, it is a basic capability of every physical resource (per the scientifically plausible, physicalist variant of pan-experientialism). However, we may question what physical states are part of human experience. We do not usually think that, for instance, the mitochondrial functions inside neurons, or the DNA, is part of the experience of the nervous system, because they do not seem to be directly participating in the main function of the nervous system: thinking. They are not part of the causal picture of thought. Likewise, we do not assume that the power supply is part of the computation in a computer. This analogy might seem out of place, initially. If pan-experientialists are right, experience is one of the basic features of the universe. It is then all around us, however, most of it is not organized as an intelligent mechanism, and therefore, correctly, we do not call them conscious. This is the simplest possible explanation of experience that has not been disproven by experiment, therefore it is a likely scientific hypothesis. It does not require any special or strange posits, merely physical resources organized in the right way so as to yield an intelligent functional mind. Consider my "evil alien" thought experiment. If tonight, an evil alien arrived and during your sleep shuffled all the connections in your brain randomly, would you still be intelligent? Very unlikely, since the connection pattern determines your brain function. You would most likely lose all of your cognition, intelligence and memory. However, one is forced to accept that even in that state, one would likely have an experience, an experience that is probably meaningless and chaotic, but an experience nonetheless. Perhaps, that is what a glob of plasma experiences. The evil alien thought experiment supports the distinction between experience and consciousness. Many philosophers mistakenly think that consciousness consists 4 in experience. That, when we understand the "mystery" of experience, we will understand consciousness. However, this is not the case. Experience is part of human-like consciousness, indeed, however, consciousness also includes a number of high-level cognitive functions such as reasoning, prediction, perception, awareness, self-reflection and so forth [Minsky, 2006, Section 4]. I suggest that it is possible that there are minds without human-like consciousness and with experience (e.g., a special purpose neural network adding numbers), and experience without any recognizable mentality. 6 Neural code vs. neural states Consider the hypothesis that experience is determined by particular neural codes. If that is true, even the experience of two humans is very different, because it has been shown that neural codes evolve in different ways Schneidman et al. [2001]. One cannot simply substitute the code from another human in someone else's brain, it will be random to the second human. And if the hypothesis is true, it will be another kind of experience, which basically means that the blue that I experience is different from the blue that you experience, while we presently think we have no way of directly comparing them. Strange as that may sound, as it is based on sound neuroscience research, it is a point of view we must take seriously. Yet even if the experiences of two humans can be very different, they must be sharing some basic quality or property of experience. Where does that come from? If experience is this complicated time evolution of electro-chemical signals, then it is in the shared nature of these electro-chemical signals (and processing) that provides the shared computational platform. Remember that a change in the neural code (spike train) implies a lot of changes. First of all, the chemical transmission across chemical synapses would change.Therefore, even a brain prosthesis device that simulates all the electrical signaling extremely accurately, might still miss part of the experience, if the bio-chemical events that occur in the brain are part of experience. Second, the electro-magnetic fields would change. Third, the computation would change, although the basic "program" of the nervous system does not change from individual to individual (neural processing does have many invariant properties, such as coding efficiency). To answer the question decisively, we must first encourage the neuroscientists to attack the problem of human experience, and find the sufficient and necessary conditions for experience to occur, or be transplanted from one person to the other. They should also find to what extent chemical reactions (or other physical events) are significant for experience. If, for instance, we find that the distinctive properties of nervous system experience crucially depend on quantum computations carried out at synapses and inside neurons, that might mean that to construct the same kind of experience you would need similar material and method of computation rather than a conventional electronic computer. Quantum computation exploits the quantum mechanical properties of matter, most notably superposition and coherence, to achieve more efficient computation than classical computation which does not use any quantum mechanical effects. The basic unit of storage in a quantum computer, qubit, relies on a quantum property known as quantum superposition, which means that all theoretical states of a quantum system exist simultaneously until measured. A qubit state is in superposition of 0 and 1 states, representing both states simultaneously, n 5 qubits are in superposition of 2n n-bit states. Superposition of a quantum system lasts until quantum decoherence, i.e., when a measurement is made Schlosshauer [2005], and the negation of that, the property of quantum states influencing each other in superposition, free from environmental interference, is called quantum coherence. Quantum computation operations transform all the states in superposition at the same time, exploiting quantum parallelism, which on particular probabilistic problems surpass the efficiency of classical computation Deutsch [1985]. The processing of qubits must be achieved while preserving quantum coherence, otherwise the quantum system turns into a classical system. A good example of another macro-scale quantum mechanical property is superconductance, which is conductance with zero resistance, and it depends on the superconductor material to exhibit quantum coherence. Recent experiments suggest that quantum coherence plays a key role in photosynthesis Panitchayangkoon et al. [2011], therefore we cannot rule out that quantum coherence might be a necessary aspect of brain operation, and brain's subjective experience. On the other hand, we need to consider the possibility that electrical signals may be a crucial part of experience, due to the power and information they encompass, so perhaps any electronic device has these electron motion patterns that make up most of your subjective experience. If that is true, the electronic devices presently would be assumed to contain brain-like experience, for instance. Then, the precise geometry and connectivity of the electronic circuit could be significant. However, it seems to me that chemical states are just as important, and if as some people hypothesize quantum phenomena play a role in the brain, it may even be possible that the quantum descriptions may be relevant. That is to say, we cannot rule out any such hypotheses a priori even if they sound uncanny. Presently, however, there does not seem to be any evidence that quantum randomness, or quantum coherence plays a role in nervous system. Another possibility is that it may be found that electromagnetic fields generated in the brain are crucial to experience, in which case the topology, amplitude, timing and other properties of electrical signaling may be relevant, i.e., anything that would change the electromagnetic field. 7 Simulation and transcoding experience At this point, the reader might be wondering if the subject were not simulation. Is the question like whether the simulation of rain is wet? In some respects, it is, because obviously, the simulation of wetness on a digital computer is not wet in the ordinary sense. 1 We may reconsider the question of experience of a brain simulation. We have a human brain A, a joyous lump of meat, and its digitized form B, running on a digital computer. Will B's experience be the same as A's, or different, or nonexistent? Up to now, if we accept the simplest theory of experience (that it requires no special conditions to exist at all), then we conclude that B will have some expe1However, we can invoke the concept of "universal quantum computer" from theory Deutsch [1985], Lloyd [1996], and claim that a universal quantum computer would re-instate wetness, relative to observers in the simulation, since a universal quantum computer is supposed to be able to perfectly simulate any finite quantum system. However, there would be only simulated wetness relative to observers outside the quantum simulation. 6 rience, but since the physical material is different, it will have a different texture to it. Otherwise, an accurate simulation, by definition, stores the same functional organization of cognitive constructs, like perception, memory, prediction, reflexes, emotions without significant information loss, and since the dreaded panpsychism may be considered possible, they might give rise to an experience somewhat similar to the human brain, yet the computer program B, may be experiencing something else at the very lowest level. Simply because it is running on some future nanoprocessor instead of the brain, the physical states have become altogether different, yet their relative relationship, i.e., the logical structure of experience, is preserved. Let us try to present the idea more intuitively. The brain is some kind of an analog/biological computer. A memorable analogy is the transfer of a 35mm film to a digital format. Surely, many critics have held that the digital format will be ultimately inferior, and indeed the medium and method of information storage is altogether different but the (film-free) digital medium also has its affordances like being able to backup and copy easily. In both kinds of film, the same information is stored, yet the medium varies. Or maybe we can contrast an analog sound synthesizer with a digital sound synthesizer. It is difficult to simulate an analog synthesizer, but you can do it to some extent. However, the physical make-up of an analog synthesizer and digital synthesizer are quite different. Likewise, B's experience will have a different physical texture but its organization can be similar, even if the code of the simulation program of B will necessarily introduce some physical difference (for instance neural signals can be represented by a binary code rather than a temporal analog signal). Perhaps, the atoms and thus, the fabric of B's experience will be different altogether as they are made up of the physical instances of computer code running on a digital computer. As improbable as it may seem today, these simulated minds will be made up of live computer codes, so it would be naive to expect that their nature will be the same as ours. They are not human brains, they are bio-information based artificial intelligences. In all likelihood, our experience would necessarily involve a degree of unimaginable features for them, as they are forced to simulate our physical make-up in their own computational architecture. This brings a degree of relative dissimilarity. And other physical differences only amplify this difference. Assuming the above explanation, therefore, when they are viewing the same scene, both A and B will claim to be experiencing the scene as they always did, and they will additionally claim that no change has occurred since the non-destructive uploading operation went successfully. This will be the case, because the state of experience is more akin to the short-term memory Minsky [1980], or RAM of computers. There is a complex electro-chemical state that is held in memory with some effort, by making the same synapses repeat firing consistently, so that more or less the same physical state is maintained. This is what must be happening when you remember something, a neural state that is somewhat similar to when the event happened should be invoked. Since in B, the texture has changed, the memory will be re-enacted in a different texture, and therefore B will have no memory of what it used to feel like being A. Within the general framework of physicalism, we can claim that further significant changes will also influence B's experience. For instance, it may be a different thing to work on hardware with less communication latency. Or perhaps if the simulation is running on a very different kind of architecture, then the physical relations may change (such as time and geometry) and this may influence B's state 7 further. We can imagine this to be asking what happens when we simulate a complex 3-D computer architecture on a 2-D chip. We must maintain, however, that strict physicalism leads us to reject the idea that no mental changes happen when significant physical changes happen. If that were possible, then we would have to reject the idea that mental states are identical to physical states, which would be dualism. Moreover, a precise answer seems to depend on a number of smaller questions that we have little knowledge or certainty of. These questions can be summarized as: 1. What is the right level of simulation for B to be functionally equivalent to A (i.e., working and responding to stimuli in the same manner)? 2. How much does the biological medium contribute to experience? 3. Does experience crucially depend on any uncanny physics like quantum coherence? I think that the right attitude to answering these finer questions is again a strict adherence to naturalism. For instance, in 3, it may seem easier to also assume a semi-spiritualist interpretation of Quantum Mechanics, and claim that the mind is a mystical, unobservable, ineffable soul. That kind of reasoning will merely help to stray away from scientific knowledge. 7.1 General physicalist perspective At this point, since we do not have conclusive scientific evidence, this is merely guesswork, and I shall give conservative answers. Question 1: If certain bio-chemical interactions are essential for the functions of emotions and sensations (like pleasure), then not simulating them adequately would result in a definite loss of functional accuracy. B would not work the same way, behaviorally, as A. This is true even if spike trains and changes in neural organization (plasticity) are simulated accurately otherwise. It is also unknown whether we can simulate at a higher level, for instance via Artificial Neural Networks, that have abstracted the physiological characteristics altogether and just use numbers and arrows to represent A, although recent brain simulation work shows that this might be possible Izhikevich and Edelman [2008a]. It is important to know these so that B does not lack some significant cognitive functions of A, such as emotions. The right level of simulation seems to be at the level of molecular interactions which would at least cover the differences among various neurotransmitters, and which we can simulate on digital computers (perhaps imprecisely, though). At least this would be necessary because we know that, for instance, neurotransmitter levels and distribution influence behavior. Thus, it would be prudent to be able to accurately simulate the neurologically relevant biochemical states and dynamics in the brain, without necessarily simulating genetics or cell operation. Recently, there has been promising work on mapping the biochemistry of the brain. Question 2: This is one question that most people avoid answering because it is very difficult to characterize. The most general characterizations may use information theory or quantum information theory. However, in general, we may say that we need an appropriate physical and informational framework to answer this question in a satisfactory manner. In the most general setting, we can claim that ultimately low-level physical states must be part of experience, because there is 8 no alternative 2. For a general physicalist, accepting a strong form of physicalism (that every mental event/property/predicate is exactly physical), it seems prudent to think that the biological medium contributes to experience insofar as it influences computational states relevant to cognition. Thus, physicalism may force us to accept that the physical details of both electrical and chemical transmission of neural signals would be significant. In other words, a good deal of neurophysics would be included, there may be no simple answer as pan-experientialists hope. Question 3: Some opponents of AI, most notably Penrose, have held that "consciousness" is due to macroscopic quantum phenomena together with Hameroff Hameroff and Penrose [1996], by which they try to explain "unity of experience". While on the other hand, many philosophers of AI think that the unity is an illusion Minsky [1991]. Yet, the illusion is something to explain, and it may well be that certain quantum interactions may be necessary for experience to occur, much like superconductivity. This again seems to be a scientific hypothesis, which can be tested. For a physicalist, thus, this is an unsettled matter, open to future research, however there is the possibility. 7.2 Pan-experientialist perspective It is my hope that the reader appreciates that pan-experientialism is indeed the simplest theory of experience that is consistent with our observations, that every physical system may have the potential for experience, regardless of the confusion that surrounds the theory. Assume that the theory is right. Then, when we ask a physicist to quantify that, she may want to measure the energy, or the amount of computation or communication, or information content, or heat, whichever works the best. A general characterization of experience such that it would hold for any physical system, may be defined precisely, and may be part of experiments. It would seem to me that the best characterization then would use information theory, because experience would not matter if it did not contain any information. For instance, an experience without any information could not contain any pictures or words. I suggest that we use such methods to clarify these finer questions. Assuming the physicalist version of pan-experientialism I may attempt to refine the answers above. The first question is not dependent on experience, it is rather a question of which processes must be simulated for correct operation, so the answer does not change. Question 2: The biological medium seems to contribute at least as much as required for correct functionality (i.e., corresponding to neural information processing and biochemical changes precisely), and at most all the information as present in the biological biochemistry (i.e., precise cellular simulations), if we subscribe to pan-experientialism. These might be significant in addition to electrical signals. The latter part might sound like a kind of vitalism but it is not, the cellular "experience" might simply constitute the low level texture of the collective experience of neural cell assemblies. Presently, it is difficult to say we know that no cellular details contribute to experience, however, we would start with the simpler former hypothesis, because there does not seem to be any good reason why we should experience the effects of parts of machinery that do not contribute to cognition (such as mitochondria), yet pan-experientialism would force us to maintain this 2The only alternative would be dualism, which is unacceptable to a physicalist 9 hypothesis, since if anything can have experience, so can the cells, and cells do have internal information processing as well, and neurons are physically part of neural information processing. Question 3: Not necessarily. According to pan-experientialism, it may be claimed to be false, since it would constrain minds to uncanny physics (and contradict with the main hypothesis). If, for instance, quantum coherence is indeed prevalent in the brain and provides much of the "virtual reality" of the brain, then the pan-experientialist could argue that quantum coherence is everywhere around us. Indeed, we may have a rather primitive understanding of coherence/decoherence processes yet, as that is itself part of the unsettled controversies in philosophy of physics. Another possibility is the use of a generalist physical approach that is compatible with pan-experientialism, such as relativity. 7.3 Further concerns Other finer points of inquiry may as well be imagined, and they are sorely needed, because our capability of analysis is limited when we cannot ask the right questions. If we forever dabble with superstitious questions, we will never have started answering our question. Thus, I have tried to show how to approach the main question, and tried to give novel answers from both a general physicalist perspective and physicalist pan-experientialism. 8 Physical basis and quantifying dissimilarity Of the sufficient and necessary physical conditions, I have naturally spent some time exploring the possibilities. I think it is quite likely that quantum interactions may be required for human experience to have the same quality as an upload's, since biology seems inventive in making use of any properties, more than we previously thought, for macro bio-molecules have been shown to have quantum behavior and quantum properties have been observed in biochemistry, i.e., photosynthesis. Maybe, Penrose is right about quantum coherence. However, specific experiments would have to be conducted to demonstrate it. It is easy to see why computational states would have to evolve, but not necessarily why they would have to depend on macro-scale quantum states (since there are classical computers), and it is an open question what this says precisely of systems that do not have any quantum coherence. Beyond Penrose, I think that the particular texture of our experience may indeed depend on chemical states, regardless of quantum coherence. If, additionally, the brain turned out to be a quantum-computer under our very noses, that would be fantastic and we could then emulate the brain states very well on artificial quantum computers. In this case, assuming that the universal quantum computer itself has little overhead, the quantum states of the upload could very closely resemble the original. Other physical conditions can be imagined, as well. For instance, digital physics provides a clear framework to discuss experience. The psychological patterns would be cell patterns in the universal cellular automata. A particular pattern may describe a particular experience. Then, two patterns are similar to the extent they are syntactically similar. Which would mean that, we still cannot say that the upload's experience will be the same. It will likely be quite different, as the patterns will vary considerably. 10 One of my nascent theories is the Relativistic Theory of Mind, which tries to explain subjectivity of experience with concepts from the theory of relativity. The principle of relativity might be a foundation for the inherent subjectivity of experience. From the general relativity viewpoint, it makes sense that different energy distributions have different experiences, since that is all that there is. What else could change? We may also consider that experience may depend on measurements, and measurements change relatively. While this falls under "uncanny physics" category, we cannot rule it out. We start with the analytical observation that all experience is subjective: there is no objective experience. The experience is always relative to an observer. However, the observer itself is not a unified entity, it is made up of components that themselves make observations relative to other components, down to the level of quanta, and each small observation incurs a delay due to the speed of light. Therefore, the brain may now be viewed as a system of microscopic subjective observers, that make observations of others, and send messages to others. Neural communication thus connects these different localities, physically. In relativity, communication cannot occur spontaneously, therefore no brain can work as a truly unified entity. However, communication obviously builds a macroscopic experience, which may manifest itself as a somewhat stable electromagnetic field which pervades the brain. It may be thought that the entire dynamics of the brain thus may be interpreted as a "virtual pocket universe" space-time with energy and topology of its own, which is difficult to observe from outside, however, occasionally there is communication with outside since it is separate but accessible. This energy distribution is part of our physical brains, but it is also the part that is intelligent (rather than metabolic), so that we realize it exists, as it continually infers information about itself and the world. According to this theory anything might have a psychological experience if it also had intelligent machinery, such as a brain simulation, however its experience would be significantly different than an original brain, since its geometry and energy distribution is likely to be quite different. This theory eliminates biochemistry borders, and predicts that there could be merging of experiences with high-bandwidth low-latency connections to machines or other nervous systems. Note that the relativistic approach originates from Einstein's thesis of separability, that physical events have locality in space-time. Thus, according to Einstein's philosophy of science, it would be impossible to imagine a mind that transcends physical limits or does not have a location (i.e., dualism), the mind consists of physical events that happen within a space-time boundary. A general description of the relative dissimilarity between two cognitive systems can be captured by algorithmic information theory. Here, the dissimilarity might correspond to saying that the similarity between A's and B's states depends on the amount of mutual algorithmic information of a complete physical description of A, and the physical description of B, i.e., how much information do the two descriptions share? As a consequence, the dissimilarity between two systems would contain the informational difference in the low-level physical structures of A and B, together with the information of the simulation program (not present in A at all), and architectural differences, which could be quite a bit if you compare nervous systems and electronic computer chips running a simulation. It seems that this difference is not so insignificant that it will not have an important contribution to experience. That is one of the reasons why I think that the answer to the question is that the brain simulation will likely have a new kind of subjective experience. There are many ways this may not be true, however, if, for instance, 11 the electromagnetic field is the body of experience, then a neural prosthesis device that accurately duplicates spike trains could reconstruct experience perfectly in principle. 9 Notes on methodology and terminology Conducting thought experiments is very important, but they should be taken with care so that the thought experiment would be scientifically plausible, even though it is very difficult or practically impossible to realize. For that reason, per ordinary philosophical theories of "mind", I go no further than neuro-physiological identity theory, which is a way of saying that your mind is literally the events that happen in your brain. Rather than being something else like a soul, a spirit, or a ghost. The reader may have also noticed that I have not used the word "qualia" because of its somewhat convoluted connotations. I did refer to the quality of experience, which is something you can think about. In all the properties that can be distinguished in this fine experience of having a mind, maybe some of them are luxurious even; and that is precisely why I used the word "quality" rather than "qualia" or "quale". I do not think that the notion that there is a family resemblance among biological brains is a troubling notion. For all we know, there should be some significant resemblance if we take physicalism seriously. Please also note that the view presented here is entirely different from Searle, who seemed to have a rather vitalist attitude towards the problem of mind. According to him, the experience vanishes, because it is not built from the right stuff, which seems to be the specific biochemistry of the brain for him Searle [1980]. Regardless of the possibility of an artificial entity to have the same biochemistry, this is still arbitrarily restrictive. Some may call this attitude carbon-chauivinism, however I think it is merely idolization of earth biology, as if it is above everything else in the universe. Acknowledgements Thanks to Ben Goertzel for his detailed comments that improved the article considerably. References D. Deutsch. Quantum Theory, the Church-Turing Principle and the Universal Quantum Computer. Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences, 400 (1818):97–117, July 1985. doi: 10.1098/rspa.1985.0070. URL http://dx.doi.org/10.1098/rspa.1985.0070. Hugo De Garis, Chen Shuo, Ben Goertzel, and Lian Ruiting. A world survey of artificial brain projects, part i: Large-scale brain simulations. Neurocomputing, 74(1-3):3–29, 2010. Ben Goertzel. Hyperset models of self, will and reflective consciousness. International Journal of Machine Consciousness, 3(1), June 2011. 12 Stuart Hameroff and Roger Penrose. 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