I say more about this here. One final comment on the likely complexity of consciousness is that, as far as I can tell, early scientific progress outside physics tends to lead to increasingly complex models of the phenomena under study. If this pattern is real, and holds true for the study of consciousness, then perhaps future accounts of consciousness will tend to be more complex than the accounts we have come up with thus far.
For more on this, see Appendix Z.
Today, we have observed multiple examples. Consider, for example, these relatively recent reported discoveries: Are these observations of sophisticated animal behavior trustworthy? In many cases, I have my doubts. Studies of animal behavior often involve very small samples sizes, no controls or poorly constructed controls , and inadequate reporting. Many studies fail to replicate. Can it all be a mirage? A second reason I suspect the trend of discovering sophisticated capacities in an ever-widening set of species is not entirely a mirage is that even the most skeptical ethologists seem to accept the general trend.
Indeed, I suspect this is generally true, given that the ethology literature seems to suffer from the same problems as medical and social science literatures do see Appendix Z. The question is: Exactly which behaviors will eventually be observed in which taxa, and how indicative of consciousness are those behaviors? We seem to be hard-wired to attribute human-like cognitive traits and emotions to non-humans, including animals, robots, chatbots, inanimate objects, and even simple geometric shapes.
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Indeed, after extensive study of the behavior of unicellular organisms, the microbiologist H. Jennings was convinced that e. Of course, a general warning about anthropomorphism is no substitute for reading through a great many examples of false anthropomorphisms, from Clever Hans onward, which you can find in the sources I list in a footnote.
However, studies of animal behavior and neurology tend to suggest the differences between human and animal experiences are much more profound than this. What is it like to be a rabbit? What is it like to be which rabbit? The rabbit on the left, or the rabbit on the right? The biologist and animal welfare advocate Marian Dawkins has expressed something close to my view on anthropomorphism, in her book Why Animals Matter :. Anthropomorphic interpretations may be the first ones to spring to mind and they may, for all we know, be correct. But there are usually other explanations, often many of them, and the real problem with anthropomorphism is that it discourages, or even disparages, a more rigorous exploration of these other explanations.
We need all the scepticism we can muster, precisely because we are all so susceptible to the temptation to anthropomorphize. Below is a high-level summary of my current thinking about the distribution-of-consciousness question with each point numbered for ease of reference :. I should say a bit more about the four factors mentioned in 7. The reasoning behind the first two factors is this: Given that I know very little about consciousness beyond the fact that humans have it, and it is implemented by information processing in brains, then all else equal, creatures that are more similar to humans, especially in their brains, are more likely to be conscious.
The reasoning behind the third factor is twofold. For example, we have many cases of apparently unconscious simple nocifensive behaviors, but I am not aware of any cases of unconscious long-term logical planning. Second, suppose we give each extant theory of consciousness a small bit of consideration. Some theories assume that consciousness requires only some very basic supporting functions e.
Here is a table showing how the animals I ranked compare on these factors according to my own quick, non-expert judgments :. But let me be clear about my process: I did not decide on some particular combination rule for these four factors, assign values to each factor for each species, and then compute a resulting probability of consciousness for each taxon. Instead, I used my intuitions to generate my probabilities, then reflected on what factors seemed to be affecting my intuitive probabilities, and then filled out this table.
However, once I created this table the first time, I continued to reflect on how much I think such weak sources of evidence should be affecting my probabilities, and my probabilities shifted around a bit as a result. Rather, this report surveys the kinds of evidence and argument that have been brought to bear on the distribution question, reports some of my impressions about those bodies of evidence and argument, and then reports what my own intuitive probabilities seem to be at this time.
Below, I try — to a limited degree — to explore why I self-report these probabilities rather than others, but of course, I have limited introspective access to the reasons why my brain has produced these probabilities rather than others. Successfully arguing for any set of probabilities about the distribution of consciousness would, I think, require a much larger effort than I have undertaken here.
In particular, I suspect the arthropods on this list, if they are conscious, might be several orders of magnitude lower in moral weight given my moral judgments than e.
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Nevertheless, I offer a few additional explanatory comments below. My guess is that to most consciousness-interested laypeople, the most surprising facts about the probabilities I state above will be that my probability of chimpanzee consciousness is so low , and that my probability of Gazami crab consciousness is so high. What might experts in animal consciousness think of my probabilities?
My guess is that most of them would think that my probabilities are too low, at least for the mammalian taxa, and probably for all the animal taxa I listed except for the arthropods. In part, this may be a result of the fact that, in my experience, I seem to be more skeptical of published scientific findings than most working scientists and philosophers are.
In any case, heightened skepticism of published studies — e. What about AlphaGo? My very low probability for AlphaGo consciousness is obviously not informed by most of the reasoning that informs my probabilities for animal species. Nevertheless, I feel I must admit some non-negligible probability that AlphaGo is conscious, given how many scholars of consciousness endorse views that seem to imply AlphaGo is conscious see below. Though even if AlphaGo is conscious, it might have negligible moral weight. Should one take action based on such made-up, poorly-justified probabilities? First, a note on how my mind did not change during this investigation.
By the time I began this investigation, I had already found persuasive my four key assumptions about the nature of consciousness : physicalism, functionalism, illusionism, and fuzziness. During this investigation I studied the arguments for and against these views more deeply than I had in the past, and came away more convinced of them than I was before. Perhaps that is because the arguments for these views are stronger than the arguments against them, or perhaps it is because I am roughly just as subject to confirmation bias as nearly all people seem to be including those who, like me, know about confirmation bias and actively try to mitigate it.
How did my mind change during this investigation? First, during the first few months of this investigation, I raised my probability that a very wide range of animals might be conscious. But, as mentioned above, I eventually lost hope that there would at this time be compelling arguments for drawing any such lines in phylogeny short of having a nervous system at all. A few months into the investigation, I began to elicit my own intuitive probabilities about the possession of consciousness by several different animal taxa. There are some other things on which my views shifted noticeably as a result of this investigation:.
Another key output of this investigation is a partial map of which activities might give me greater clarity about the distribution of consciousness see the next section. A third key output from this investigation is that we decided months ago to begin investigating possible grants targeting fish welfare.
As such, I could find little justification for suggesting that there is a knowably large difference between the probability of chicken consciousness and the probability of fish consciousness. Furthermore, humans harm and kill many, many more fishes than chickens, and some fish welfare interventions appear to be relatively cheap. For example, I have yet to examine other potential criteria for moral patienthood besides consciousness, and I have not yet examined the question of moral weight see above. The question of moral weight, especially, could eventually undermine the case for fish welfare grants, even if the case for chicken welfare grants remains robust.
Nevertheless, and consistent with our strategies of hits-based giving and worldview diversification , we decided to seek opportunities to benefit fishes in case they should be considered moral patients with non-negligible weight. There are many things I considered doing to reduce my own uncertainty about the likely distribution of morally-relevant consciousness, but which I ended up not doing, due to time constraints.
I may do some of these things in the future. For a higher-level overview of scientific work that can contribute to the development of more satisfying theories of consciousness, see Chalmers So far, the topic has been fairly neglected, though several recent books on the topic may begin to help change that. Efforts on the distribution question and illusionist approaches to consciousness could be expanded via workshops, conferences, post-doctoral positions, etc.
There are also many projects that I would likely suggest as high-priority if I knew more than I do now. Consciousness is very likely a phenomenon to be explained at the level of neural networks and the information processes they instantiate, but our our current tools are not equipped to probe that level effectively. Some of them would require steady, dedicated work from a moderately large team of experts over the course of many years. But, it seems to me the problem of consciousness is worth a lot of work, especially if you share my intuition that it may be the most important criterion for moral patienthood.
A good theory of human consciousness could help us understand which animals and computer programs we should morally care about, and what we can do to benefit them. Without such knowledge, it is difficult for altruists to target their limited resources efficiently.
Nor do I conceive of myself as merely expressing my moral feelings as they stand today. Hence, in sharing my intuitions about moral patients below, I see no way to escape the limitation that they are merely my moral judgments. Nevertheless, I suspect many readers will feel that they have similar but not identical moral intuitions. However, I should note that I very rarely engage all the time-consuming cognitive operations described below when making moral judgments, and I did not engage all of them when making the moral judgments reported in this appendix.
Nevertheless, here it is:. What, then, do my moral intuitions say about some specific cases? The starting point for my moral intuitions is my own phenomenal experience. Likewise, the reason I want others to flourish is that I know what it feels when I taste chocolate ice cream, or when I feel euphoric, or when I achieve my goals, and I do want others to have experiences like that. Earlier , I gave the example of injuring myself while playing sports, but not noticing my injury and its attendant pain until 5 seconds after the injury occurred, when I exited my flow state.
Had such a moment been caught on video, I suspect the video would show that I had been unconsciously favoring my hurt ankle while I continued to chase after the ball, even before I realized I was injured, and before I experienced any pain. Would I consider such a conscious existence to have moral value? Keep in mind this is just an illustration: if fishes are conscious at all, then my guess is that they experience at least some nociception as unpleasant pain rather than as an unbothersome signal like the pain asymbolic does.
This last example is similar to a thought experiment invented by Peter Carruthers, which I consider next. Carruthers presents an interesting intuition pump concerning consciousness and moral patienthood:. So when he achieves a goal he does not experience any warm glow of success, or any feelings of satisfaction.
And when he believes that he has failed to achieve a goal, he does not experience any pangs of regret or feelings of depression. Nevertheless, Phenumb has the full range of attitudes characteristic of conscious desire-achievement and desire-frustration. So when Phenumb achieves a goal he often comes to have the conscious belief that his desire has been satisfied, and he knows that the desire itself has been extinguished; moreover, he often believes and asserts that it was worthwhile for him to attempt to achieve that goal, and that the goal was a valuable one to have obtained.
Similarly, when Phenumb fails to achieve a goal he often comes to believe that his desire has been frustrated, while he knows that the desire itself continues to exist now in the form of a wish ; and he often believes and asserts that it would have been worthwhile to achieve that goal, and that something valuable to him has now failed to come about. Notice that Phenumb is not or need not be a zombie. That is, he need not be entirely lacking in phenomenal consciousness. On the contrary, his visual, auditory, and other experiences can have just the same phenomenological richness as our own; and his pains, too, can have felt qualities.
What he lacks are just the phenomenal feelings associated with the satisfaction and frustration of desire. Perhaps this is because he is unable to perceive the effects of changed adrenaline levels on his nervous system, or something of the sort. Is Phenumb an appropriate object of moral concern? I think it is obvious that he is. While it may be hard to imagine what it is like to be Phenumb, we have no difficulty identifying his goals and values, or in determining which of his projects are most important to him — after all, we can ask him!
When Phenumb has been struggling to achieve a goal and fails, it seems appropriate to feel sympathy: not for what he now feels — since by hypothesis he feels nothing, or nothing relevant to sympathy — but rather for the intentional state which he now occupies, of dissatisfied desire. Similarly, when Phenumb is engaged in some project which he cannot complete alone, and begs our help, it seems appropriate that we should feel some impulse to assist him: not in order that he might experience any feeling of satisfaction — for we know by hypothesis that he will feel none — but simply that he might achieve a goal which is of importance to him.
What the example reveals is that the psychological harmfulness of desire-frustration has nothing or not much — see the next paragraph to do with phenomenology, and everything or almost everything to do with thwarted agency. The qualifications just expressed are necessary, because feelings of satisfaction are themselves often welcomed, and feelings of dissatisfaction are themselves usually unwanted.
Since the feelings associated with desire-frustration are themselves usually unpleasant, there will, so to speak, be more desire-frustration taking place in a normal person than in Phenumb in any given case. For the normal person will have had frustrated both their world-directed desire and their desire for the absence of unpleasant feelings of dissatisfaction. But it remains true that the most basic, most fundamental, way in which desire-frustration is bad for, or harmful to, the agent has nothing to do with phenomenology.
Phenumb might, of course, be a moral patient via other criteria. Carruthers suggests a reason why some people like me might have a different moral intuition about this case than he does:. What emerges from the discussions of this paper is that we may easily fall prey to a cognitive illusion when considering the question of the harmfulness to an agent of non-conscious frustrations of desire. In fact, it is essentially the same cognitive illusion which makes it difficult for people to accept an account of mental-state consciousness which withholds conscious mental states from non-human animals.
In both cases the illusion arises because we cannot consciously imagine a mental state which is unconscious and lacking any phenomenology. When we imagine the mental states of non-human animals we are necessarily led to imagine states which are phenomenological; this leads us to assert… that if non-human animals have any mental states at all…, then their mental states must be phenomenological ones.
In the same way, when we try to allow the thought of non-phenomenological frustrations of desire to engage our sympathy we initially fail, precisely because any state which we can imagine, to form the content of the sympathy, is necessarily phenomenological; this leads us… to assert that if non-human animals do have only non-conscious mental states, then their states must be lacking in moral significance. In both cases what goes wrong is that we mistake what is an essential feature of conscious imagination for something else — an essential feature of its objects, in the one case hence claiming that animal mental states must be phenomenological ; or for a necessary condition of the appropriateness of activities which normally employ imagination, in the other case hence claiming that sympathy for non-conscious frustrations is necessarily inappropriate.
Once these illusions have been eradicated, we see that there is nothing to stand in the way of the belief that the mental states of non-human animals are non-conscious ones, lacking in phenomenology. And we see that this conclusion is perfectly consistent with according full moral standing to the [non-conscious, according to Carruthers] sufferings and disappointments of non-human animals.
These patients are as far as we can tell phenomenally conscious like normal humans are, but — at least during the period of time when their AAD symptoms are most acute — they report having approximately no affect or motivation about anything. Several case reports see Appendix G describe AAD patients as being capable of playing games if prompted to do so. Suppose we could observe an AAD patient named Joan, an avid chess player. Next, suppose we prompted her to play a game of chess, waited until some point in the midgame, and then asked her why she had made her latest move.
Has anything morally negative happened to Joan? Is there now a moral good realized when Joan, say, wins a chess game or accomplishes some other goal? She has goals and aversions, and she can talk to you about them. Hence, it is easier to state my moral intuitions about computer programs , especially when I have access to their source code, or at least have a rough sense of how they were coded.
As a functionalist , I believe that the right kind of computer program would be conscious, regardless of whether it was implemented via a brain or brain-like structure or implemented some other way. In the course of reporting some of my moral intuitions, I will also try to illustrate the problematic vagueness of psychological terms more on this below.
For example, consider the short program below, written in Python version 3. Thus, comments do not affect how the program runs. My moral intuitions are such that I do not care about this program, at all. This program does not experience pain. I think not. In contrast, computer code is precise.
Consider, for example, the algorithm controlling Mario in the animation below: Animation captured by the author from a video by Robin Baumgarten. Very sophisticated behavior! But these are just isolated cases, and there is a more systematic way we can examine our intuitions about moral patients, and explore the problematic vagueness of psychological terms, using computer code — or at least, using a rough description of code that we are confident experienced programmers could figure out how to write. We can start with a simple program, and then gradually add new features to the code, and consult our moral intuitions at each step along the way.
The next section probably also helps to illustrate what I find unsatisfying about all current theories of consciousness, a topic I discuss in more detail in Appendix B. To get to the exit of each tile-based level, you must navigate the Hero character through the level, picking up items e. See animated screenshot. I wrote the code to add some additional interactive objects to the game, so I have some idea of how the game works at a source-code level. First, a message is passed to check whether the Hero object has a Shield in its inventory.
If it does, nothing happens. If the Hero object does not have a Shield, then the Hero object is removed from the level and a new HeroDead object — which looks like the Hero lying down beneath a gravestone — is placed on the same tile. Did anything morally bad happen, there?
The Worm is the purple moving object in the animated screenshot. In this case, the Worm will be facing diagonally toward the Hero, and will try to move to F4 diagonal moves are allowed. And if there are obstacles on all those tiles, it will stay put. I imagine you have these same intuitions.
Planning Hero : Imagine the Hero object is programmed to find its own path through the levels. Alternately, the program could use a belief-desire-intention BDI architecture to enable its planning. Now is the Hero object a moral patient? Does this version of the program satisfy any popular accounts of consciousness or moral patienthood?
Again, it depends on how we interpret vague psychological terms. How would the program need to be different in order for it to have such a belief? One might also wonder whether the Hero object in this version of the program satisfies some interpretations of the core Kantian criterion for moral patienthood, that of rational agency. Is the Hero object now a moral patient? The Hero also has one opportunity to move per second. Now, instead of objects interacting by checking at each time step whether they are located on the same tile as another object, there is instead a collision detection algorithm run by every object to check whether another object has at least one pixel overlapping with one of its own pixels.
I still think not. Nociception and nociceptive reflexes : Now, suppose we give the Hero object nociceptors. Naturally, the Hero might fail to move in this direction because it detects an obstacle on that tile, in which case it will stay put. Or there might be a Worm or other enemy on that tile. Is the Hero object a moral patient now? Health meter : Next, we give the Hero object an integer-type variable called SelfHealth, which initializes at When it reaches 0, the Hero object is replaced with the HeroDead object. Now is the Hero a moral patient? Nociception sent to a brain : Now, a new sub-object of the Hero, called Brain, is the object that can call the NociceptiveReflex function.
If a nociceptor detects a collision, it creates a new object called NociceptiveSignal, which thereafter moves at a speed of 1 pixel per 0. Is the Hero object, finally, a moral patient? What program would satisfy one or more of her indicators of consciousness? And yet, when I carry out that exercise in my head , I typically do not end up having the intuition that any of those versions of the MESH: Hero code — especially those described above — are conscious, or moral patients.
In the future, I hope to describe this program in some detail, and then show how my moral intuitions respond to various design tweaks, but we decided this exercise fell beyond the scope of this initial report on moral patienthood. In this appendix, I describe some popular theories of human consciousness, explain the central reason why I find them unsatisfying, and conclude with some thoughts about how a more satisfying theory of consciousness could be constructed.
There is still much work to be done…. Neuroscientist Michael Graziano states the issue more vividly and less charitably : I was in the audience watching a magic show. Per protocol a lady was standing in a tall wooden box, her smiling head sticking out of the top, while the magician stabbed swords through the middle. The boy must have been about six or seven.
There is still much work to be done. As I said earlier , I think a successful explanation of consciousness would show how the details of some theory predict, with a fair amount of precision, the explananda of consciousness — i. This is, after all, a normal way to make progress in science: propose a simple model, use the model to make novel predictions, test those predictions, revise the model in response to experimental results, and so on. Of the modern theories of consciousness, the first one Graziano complains about ch. The idea… goes something like this: the brain is composed of neurons that pass information among each other.
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Information is more efficiently linked from one neuron to another, and more efficiently maintained over short periods of time, if the electrical signals of neurons oscillate in synchrony. Therefore, consciousness might be caused by the electrical activity of many neurons oscillating together. This theory has some plausibility. Maybe neuronal oscillations are a precondition for consciousness. But note that… the hypothesis is not truly an explanation of consciousness. It identifies a magician. Suppose that neuronal oscillations do actually enhance the reliability of information processing.
That is impressive and on recent evidence apparently likely to be true. But by what logic does that enhanced information processing cause the inner experience? Why an inner feeling? Why should information in the brain — no matter how much its signal strength is boosted, improved, maintained, or integrated from brain site to brain site — become associated with any subjective experience at all? Why is it not just information without the add-on of awareness? I should note that Graziano is too harsh, here. As Graziano says elsewhere :.
I think this is a good test for theories of consciousness: If you described your theory of consciousness to a team of software engineers, machine learning experts, and roboticists, would they have a good idea of how they might, with several years of work, build a robot that functions according to your theory? And would you expect it to be phenomenally conscious, and additionally stipulating some reasonable mechanism for forming beliefs or reports to believe or report itself to have phenomenal consciousness for reasons that are fundamentally traceable to the fact that it is phenomenally conscious?
For a similar attitude toward theories of consciousness, see also the illusionist-friendly introductory paragraph of Molyneux :. In this way, Minsky hoped, we might at least explain why we are confused. Since a good way to explain something is often to build it, a good way to understand our confusion [about consciousness] may be to build a robot that thinks the way we do… I hope to show how, by attempting to build a smart self-reflective machine with intelligence comparable to our own, a robot with its own hard problem, one that resembles the problem of consciousness, may emerge.
Oizumi et al. Integrated information theory IIT approaches the relationship between consciousness and its physical substrate by first identifying the fundamental properties of experience itself: existence, composition, information, integration, and exclusion. IIT then postulates that the physical substrate of consciousness must satisfy these very properties. We develop a detailed mathematical framework in which composition, information, integration, and exclusion are defined precisely and made operational. This allows us to establish to what extent simple systems of mechanisms, such as logic gates or neuron-like elements, can form complexes that can account for the fundamental properties of consciousness.
Based on this principled approach, we show that IIT can explain many known facts about consciousness and the brain, leads to specific predictions, and allows us to infer, at least in principle, both the quantity and quality of consciousness for systems whose causal structure is known. For example, we show that some simple systems can be minimally conscious, some complicated systems can be unconscious, and two different systems can be functionally equivalent, yet one is conscious and the other one is not.
I have many objections to IIT, for example that it predicts enormous quantities of consciousness in simple systems for which we have no evidence of consciousness. Graziano provides the following example: Tononi emphasizes the case of anesthesia. As a person is anesthetized, integration among the many parts of the brain slowly decreases, and so does consciousness… But even without doing the experiment, we already know what the result must be. As the brain degrades in its function, so does the integration among its various parts and so does the intensity of awareness. But so do most other functions.
Even many unconscious processes in the brain depend on integration of information, and will degrade as integration deteriorates. The underlying difficulty here is… the generality of integrated information. Integrated information is so pervasive and so necessary for almost all complex functions in the brain that the theory is essentially unfalsifiable. Whatever consciousness may be, it depends in some manner on integrated information and decreases as integration in the brain is compromised.
Indeed, as far as I can tell, IIT proponents think that a great many brain processes typically thought of as paradigm cases of unconscious cognitive processing are in fact conscious, but we are unaware of this. The only objective, physically measurable truth we have about consciousness is that we can, at least sometimes, report that we have it. In discussion with colleagues, I have heard the following argument… The brain has highly integrated information. Highly integrated information is so the theory goes consciousness.
Problem solved. Why do we need a special mechanism to inform the brain about something that it already has? The integrated information is already in there; therefore, the brain should be able to report that it has it. The integrated information theory of consciousness does not explain how the brain, possessing integrated information and, therefore, by hypothesis, consciousness , encodes the fact that it has consciousness, so that consciousness can be explicitly acknowledged and reported.
The information is all of a type that a sophisticated visual processing computer, attached to a camera, could decode and report. To get around this difficulty and save the integrated information theory, we would have to postulate that the integrated information that makes up consciousness includes not just information that depicts the apple but also information that depicts what a conscious experience is, what awareness itself is, what it means to experience.
The two chunks of information would need to be linked. Then the system would be able to report that it has a conscious experience of the apple…. Weisberg , ch. Perhaps the best developed empirical theory of consciousness is the global workspace view Baars ; It will operate automatically along relatively fixed lines.
However, if the state is conscious, it connects with the rest of our mental lives, allowing for the generation of far more complex behavior. The global workspace GWS idea takes this initial insight and develops a psychological theory — one pitched at the level of cognitive science, involving a high-level decomposition of the mind into functional units. The view has also been connected to a range of data in neuroscience, bolstering its plausibility…. So, how does the theory go? First, the GWS view stresses the idea that much of our mental processing occurs modularly.
A prime example is how the early vision system works to create the 3-D array we consciously experience. But this increase in speed leads to the possibility of error when the situation is not as the visual system assumes. This is because the process of detecting the lines takes the vertices where the points attach to the lines as cues about depth.
Modularity is held to be a widespread phenomenon in the mind. Just how widespread is a matter of considerable debate, but most researchers would accept that at least some processes are modular, and early perceptual processes are the best candidates. The idea of the GWS is that the workspace allows us to connect and integrate knowledge from a number of modular systems. This gives us much more flexible control of what we do. And this cross-modular integration would be especially useful to a mind more and more overloaded with modular processes.
Hence, we get an evolutionary rationale for the development of a GWS: when modular processing becomes too unwieldy and when the complexity of the tasks we must perform increases, there will be advantages to having a cross-modular GWS. Items in the global workspace are like things posted on a message board or a public blog. All interested parties can access the information there and act accordingly. They can also alter the info by adding their own input to the workspace. The GWS is also closely connected to short-term working memory.
Things held in the workspace can activate working memory, allowing us to keep conscious percepts in mind as we work on problems. Also, the GWS is deeply intertwined with attention. We can activate attention to focus on specific items in the network. But attention can also influence what gets into the workspace in the first place.
To return to a functionalist way of putting things, if a system does what the GWS does, then the items in that system are conscious.
This is the functional mark of consciousness. What, exactly, is a conscious state, according to Dehaene? These neurons are distributed in many brain areas, and they all code for different facets of the same mental representation. Becoming aware of the Mona Lisa involves the joint activation of millions of neurons that care about objects, fragments of meaning, and memories. Conscious perception is complete when they converge. And so on. Indeed, on my view, it is quite plausibly the case that consciousness depends on integrated information and higher-order representations.
The problem is just that none of these ideas, or even all of these ideas combined , seem sufficient to explain, with a decent amount of precision, most of the key features of consciousness we know about. Perhaps an algorithm inspired by Kammerer could instantiate this feature of human consciousness. One major limitation of [illusionism as described by Frankish] is that it does not offer any mechanisms for how the illusion of phenomenal feelings works. It is much, much harder to explain how the illusion was created. Illusionism can be a useful theory if mechanisms are put forth that explain how the brain creates an illusion of phenomenal feelings….
If I were a career consciousness theorist, I think this is how I would try to make progress toward a theory of consciousness, given my current intuitions about what is most likely to be successful:. Coding a virtual agent that really acted like a conscious human, including in its generated speech about qualia, might be an AI-complete problem.
Perhaps this process sounds like a lot of work. Surely, it is. But it does not seem impossible. In fact, it is not too dissimilar from the process Bernard Baars, Stan Franklin, and others have used to implement global workspace theory in the LIDA cognitive architecture. In this appendix, I summarize much of the evidence cited in favor of the theory that human visual processing occurs in multiple streams, only one of which leads to conscious visual experience, as described briefly in an earlier section.
To simplify the exposition, I present here only the positive case for this theory, even though there is also substantial evidence that challenges the theory see below , and thus I think we should only assign it or something like it moderate credence. A single-cell organism like the Euglena , which lives in ponds and uses light as a source of energy, changes its pattern of swimming according to the different levels of illumination it encounters in its watery world. Such behavior keeps Euglena in regions of the pond where an important resource, sunlight, is available. The simplest and most obvious way to understand this behavior is that it works as a simple reflex, translating light levels into changes in the rate and direction of swimming.
Of course, a mechanism of this sort, although activated by light, is far less complicated than the visual systems of multicellular organisms. But even in complex organisms like vertebrates, many aspects of vision can be understood entirely as systems for controlling movement, without reference to perceptual experience or to any general-purpose representation of the outside world. Vertebrates have a broad range of different visually guided behaviors.
What is surprising is that these different patterns of activity are governed by quite independent visual control systems. These modules run on parallel tracks from the eye right through the brain to the motor output systems that execute the behavior. The optic nerves that brought information from the eye to the optic tectum on the damaged side of the brain were severed by this surgery. A few weeks later, however, the cut nerves re-grew, but finding their normal destination missing, crossed back over and connected with the remaining optic tectum on the other side of the brain.
But this did not mean that their entire visual world was reversed. This part of the brain, which sits just in front of optic tectum, is called the pretectum. Ingle was subsequently able to selectively rewire the pretectum itself in another group of frogs. These animals jumped right into an obstacle placed in front of them instead of avoiding it, yet still continued to show normal prey catching.
There is no sensible answer to this. Once you accept that there are separate visuomotor modules in the brain of the frog, the puzzle disappears. We now know that there are at least five separate visuomotor modules in the brains of frogs and toads, each looking after a different kind of visually guided behavior and each having distinct input and output pathways. Evidence for this can be seen even in the anatomy of the visual system.
Each of these brain structures in turn gives rise to a distinctive set of outgoing connections. The existence of these separate input—output lines in the mammalian brain suggests that they may each be responsible for controlling a different kind of behavior — in much the same way as they are in the frog. The mammalian brain is more complex than that of the frog, but the same principles of modularity still seem to apply.
In rats and gerbils, for example, orientation movements of the head and eyes toward morsels of food are governed by brain circuits that are quite separate from those dealing with obstacles that need to be avoided while the animal is running around. In fact, each of these brain circuits in the mammal shares a common ancestor with the circuits we have already mentioned in frogs and toads. Even with the evolution of the cerebral cortex this remained true, and in mammals such as rodents the major emphasis of cortical visual processing still appears to be on the control of navigation, prey catching, obstacle avoidance, and predator detection [ Dean ].
It is probably not until the evolution of the primates, at a late stage of phylogenetic history, that we see the arrival on the scene of fully developed mechanisms for perceptual representation. The transformations of visual input required for perception would often be quite different from those required for the control of action.
They evolved, we assume, as mediators between identifiable visual patterns and flexible responses to those patterns based on higher cognitive processing. Given the evidence for multiple, largely independent vision systems in simpler animals, it should be no surprise that primates, too, have multiple, largely independent vision systems. Fortunately, her partner Carlo soon arrived home and rushed her to the hospital. She could see colors and surface textures e. This was confirmed in formal testing.
She could see detail. Is it some sort of kitchen utensil? Dee often had trouble separating an object from the background. Illustration by the Open Philanthropy Project. In none of these cases was she able to reliably detect objects or shapes, though she could report the colors accurately. For each round of the test, Dee was shown a pair of these shapes and asked to say whether they were the same or different.
When we used any of the three rectangles that were most similar to the square, she performed at chance level. She sometimes even made mistakes when we used the most elongated rectangle, despite taking a long time to decide. Under each rectangle [in the image below] is the number of correct judgments out of 20 that Dee made in a test run with that particular rectangle.
Dee has great difficulties in copying drawings of common objects or geometric shapes [see image below]. Some brain-damaged patients who are unable to identify pictures of objects can still slavishly copy what they see, line by line, and produce something recognizable. When she tried to copy those objects middle column , she could incorporate some elements of the drawing such as the small dots representing text , but her overall copies are unrecognizable. However, when asked to draw objects from memories she formed before her accident right-most column , she did just fine, except for the fact that when she lifted her pencil and put it back down, she sometimes put it back down in the wrong place presumably due to her inability to see shapes and edges even as she was drawing them.
Waking up from dreams like this, especially in the early years, was a depressing experience for her. Remembering her dream as she gazed around [her now edgeless, shapeless, object-less] bedroom, she was cruelly reminded of the visual world she had lost. However, despite her severe deficits in identifying shapes, objects, and people, Dee displayed a nearly normal ability to walk around in her environment and use her hands to pick things up and interact with them.
In fact, she had no idea whether we were holding it horizontally or vertically. But then something quite extraordinary happened. Before we knew it, Dee had reached out and taken the pencil, presumably to examine it more closely… After a few moments, it dawned on us what an amazing event we had just witnessed. By performing this simple everyday act she had revealed a side to her vision which, until that moment, we had never suspected was there. Yet it was no fluke: when we took the pencil back and asked her to do it again, she always grabbed it perfectly, no matter whether we held the pencil horizontally, vertically, or obliquely.
How could Dee do this? However, when she was asked to merely turn the card so that it matched the orientation of the slot, without reaching toward the slot, she performed no better than chance. When a normal patient is asked to reach out and grab an object on a table, they open their fingers and thumb as soon as their hand leaves the table. Thereafter, they begin to close their fingers and thumb so that a good grasp is achieved see right. The MGA is always larger than the width of the target object, but the two are related: the bigger the object, the bigger the MGA.
As expected, her grasping motions showed the same mid-flight grip scaling as those of healthy controls, and she grasped the Efron blocks just as smoothly as anyone else. She performed just fine regardless of the orientation of Efron blocks, and she effortlessly rotated her wrist to grasp them width-wise rather than length-wise just like healthy subjects. When asked to estimate, with her thumb and forefinger, the width of a familiar object stored in her memory, such as a golf ball, she did fine.
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Again, Dee could reach out and grasp these objects just as well as healthy controls, even though she was unable to say whether pairs of the Blake shapes were the same or different. They visited a laboratory in which obstacles of various heights could be placed along a path, and sophisticated equipment could precisely measure the adjustments people made to their gait to step over the obstacles. Once again, Dee performed just like healthy subjects, stepping confidently over the obstacles without tripping, just barely clearing them again, like healthy subjects. However, when asked to estimate the height of these obstacles, she performed terribly.
The most amazing thing about Dee is that she is able to use visual properties of objects such as their orientation, size, and shape, to guide a range of skilled actions — despite having no conscious awareness of those same visual properties. This… indicates that some parts of the brain which we have good reason to believe are badly damaged in Dee play a critical role in giving us visual awareness of the world while other parts relatively undamaged in her are more concerned with the immediate visual control of skilled actions.
Indeed there are: The patient was a middle-aged man who suffered a massive stroke to both sides of the brain in a region called the parietal lobe… He could recognize objects and people, and could read a newspaper. He did tend to ignore objects on his left side and had some difficulty moving his eyes from one object to another. But his big problem was not a failure to recognize objects, but rather an inability to reach out and pick them up. Instead of reaching directly toward an object, he would grope in its general direction much like a blind man, often missing it by a few inches.
But it turned out that the patient showed the problem only when he used his right hand. When he used his left hand to reach for the same object, his reaches were pretty accurate. This means that there could not have been a generalized problem in seeing where something was. He deduced this from asking the patient to point to different parts of his own body using his right hand with his eyes closed: there was no problem. Subsequent work in their laboratory went on to show that the reaching and pointing errors made by many patients with optic ataxia are most severe when they are not looking directly at the target.
But even when pointing at a target in the center of the visual field, the patients still make bigger errors than normal people do, albeit now on the order of millimeters rather than centimeters. Patients with optic ataxia also have difficulty avoiding collisions with obstacles as they reach for an object. For example, neuroscientist Robert McIntosh designed a test in which subjects are asked to reach from a fixed starting point to a strip 25cm away, between two vertical rubber cylinders.
The location of the cylinders is varied, and healthy control subjects always vary their reach trajectory so as to stay well clear of the rubber cylinders. In contrast, optic ataxia patients do not vary their reach trajectory in response to where the rubber cylinders are located, and thus often come somewhat close to knocking over the rubber cylinders as they reach for the strip at the back of the table.
However, the failure of patients with optic ataxia to adjust their reach trajectory in response to the location of the cylinders is not due to a failure to consciously see where the cylinders are. When asked to point to the midpoint between the two cylinders, patients with optic ataxia are just as accurate as healthy controls. Morris Harvey has damage in his left parietal lobe, which means that his optic ataxia affects only his right hand, and only when reaching toward objects in his right visual field.
How did Morris perform at the cylinders task? When reaching with his left hand, his reach trajectory was the same as healthy subjects, adjusted to maximally avoid the cylinders. Wimbledon: Barty makes short work of Dart, but Millman exits. Second earthquake to hit California is the strongest in 20 years. Property market cools as home loans tumble. Today's Stories. There was an error submitting the form. Please try again. First Name this. Last Name this. Email Address this. Gender Female Male Other Required.