However, meta-level questions arise for the pluralists: what relation holds between those notions of consciousness? Are they different aspects of a single phenomenon, or do they refer to different phenomena? The second question is the phenomenological question: What phenomenological features does consciousness have? This question is divided into three subquestions: content, dimension, and structure. There are three approaches to each subquestion: I introspection approach , II observation approach , and III reasoning approach.
Thus, introspection in this sense can include imagining a conscious experience and conceptually describing its phenomenological feature; it can also involve imaginatively comparing a current conscious experience with past conscious experiences 5. The introspection approach works for basic contents of conscious experiences and their salient dimensions and structures.
For instance, when I introspect on my current conscious experience of drinking Springbank 15 years, I can find that it has sweetness, smokiness, saltiness, and its distinctive sulfur smell as its flavor contents, that it has temporal continuity as its structure, and that it has perceptual and algedonic dimensions.
However, there are cases for which the introspection approach does not work. For instance, sophisticated skills of introspection are required to capture the complex phenomenological features of consciousness such as dynamical interactions of attentional shifts and flavor profiles of drinking Springbank 15 years, but people typically lack such skills. Furthermore, introspection seems unable to determine whether a perceptual experience can have causal relations e.
This is not because our skills of introspection are not sophisticated to the required extent, but because it is unclear how introspective data are related to these issues. We need to clarify what introspective data are predicted if we consciously experience causal relations between events in addition to experiencing sequential occurrences of events, if we consciously experience the property of being water in addition to experiencing the presence of clear, colorless liquid, and if consciousness has a cognitive dimension as being irreducible to other dimensions such as sensory and imaginative ones.
Introspection turns out useless if no introspectable difference is predicted there. For instance, it is hard for normal people to understand by introspection the phenomenological features of schizophrenic experiences and synesthetic experiences.
For instance, when one reports that she sees a red patch, then we can infer that her conscious experience has red-color content; when one groans painfully, we can infer that she has pain experience 6. This approach is available to explore the phenomenological features of conscious experiences that are difficult for researchers to have by themselves, such as schizophrenic and synesthetic experiences.
Experimental neuroscience of consciousness typically employs the observation approach in investigating neural properties responsible for the phenomenological features of conscious experiences Tononi and Koch, , sec. This is in part because it needs to collect quantitative data about neural activities from many experimental participants rather than the researchers themselves alone.
In addressing untypical conscious experiences, even the introspective reports of such experiences are difficult to interpret. The reasoning approach infers what phenomenological features consciousness has from a given thesis about consciousness.
For instance, Pitt argues that given that the possession of consciousness enables us to introspectively know what we think, consciousness must have a cognitive dimension as being irreducible to other dimensions 7. A challenge to those who adopt this approach is to justify a thesis about consciousness used as a premise for reasoning. As shown in this, answers to other kinds of questions, in particular, the ontological question and the axiological question , can possibly be the premises used in the reasoning approach.
The third question is the epistemological question: How do we know about consciousness? There are three approaches to the epistemological question: I first-person descriptive approach , II third-person descriptive approach , and III betterment approach. The first-person descriptive approach describes how we know about our own consciousness and the consciousness of others from the first-person perspective.
If a theory of introspection implies that introspection is entirely distinct from perceptual awareness, the theory seems to conflict with the transparency of perceptual experience and therefore be assessed negatively. The third-person descriptive approach describes how we know about our own consciousness and the consciousness of others from the third-person perspective.
A theory of introspection can also be evaluated based on the relevant scientific findings. This approach includes attempts to describe the processes of mind reading and empathy. The betterment approach explores how we can better know about consciousness, rather than just describing how we know about it.
There are a few research projects that can be counted as the betterment approach. Some training programs to enhance the skills of empathy have been developed Lam et al. Likewise, there is a research project to design a training program to enhance the skills of introspection in general Miyahara et al. There are also many attempts to invent an interview-based method to know better what others consciously experience Petitmengin, ; Langdridge, ; Giorgi, ; Petitmengin et al.
Importantly, we can see the betterment approach as developing methods to address the phenomenological question 8. The fourth question is the ontological question: How is consciousness located in the world? This question is divided into two subquestions. The first is the mind—body question: What relation holds between consciousness and the physical world in particular our brain? The second is the distribution question: How is consciousness distributed in the physical world?
There are two approaches to the mind—body question: I correlation approach and II reasoning approach. There are also two approaches to the distribution question: I intuition approach and II reasoning approach. The correlation approach explores what neural or informational feature is correlated with the presence of a phenomenological feature of consciousness or the presence of consciousness itself by using brain scanning technologies such as functional magnetic resonance imaging fMRI and brain stimulation techniques such as repetitive transcranial magnetic stimulation rTMS.
There are many findings of the neural and informational correlates of consciousness Koch et al. The limitation of the correlation approach is that it cannot, in principle, reveal a more substantial relationship between consciousness and the physical world than the correlation relation.
Since the correlation relation is consistent with many metaphysical relations such as causal relation, grounding relation, and identity relation, the correlation approach cannot determine which metaphysical relation holds between consciousness and the physical world Kozuch and Kriegel, The reasoning approach infers what relation holds between consciousness and the physical world from a given thesis about consciousness.
For example, Papineau , pp. Chalmers , pp. Campbell , chap. As shown in these examples, the reasoning approach can address what metaphysical relation holds between consciousness and the physical world beyond mere correlation. The essential difficulty with the reasoning approach is to settle the conflicts between those who take distinct theses, which are justified in different manners, as the premises to infer opposing ontological positions such as physicalism and anti-physicalism.
The intuition approach to the distribution question asks our intuition what has consciousness. We typically have some intuitive thoughts about what can have consciousness. For instance, it seems doubtless to me that other human beings are conscious. Many other kinds of mammals, such as dogs and cats, seem to have consciousness. However, microphysical entities and machines like my laptop do not seem to have consciousness.
It is unclear to me whether insects and plants are conscious. On the assumption that intuition is a reliable epistemic route to know about the distribution of consciousness over the world, we can employ our intuition to answer the distribution question.
The obvious problem with this approach is to justify the assumption that intuition is reliable with respect to the distribution of consciousness over the world. The reasoning approach is also available to address the distribution question: to infer what has consciousness from a given thesis about consciousness. For example, if we take biological naturalism that consciousness is a biological phenomenon Searle, as a premise for reasoning, we can infer that non-biological entities, such as machines and robots, cannot have consciousness.
As we have seen, the essential difficulty with this approach is to settle the debates between those who take distinct theses, which are justified in different manners, as the premises for reasoning. Note that the answer to the distribution question directly affects the scope of the phenomenological and epistemological questions.
For instance, since IIT implies that computers which generate information in an integrated manner possess consciousness, the question of how we can know about the consciousness of such computers arises for advocates of IIT. Likewise, IIT opens up the phenomenological question about such computers: What content, dimension, and structure does their consciousness have?
The fifth question is the axiological question: What values does consciousness have? This question is divided into four subquestions depending on what kind of value to address: cognitive, epistemic, moral, and esthetic. The scope of those subquestions is not restricted to the values of consciousness itself but includes those of each content, dimension, and structure of consciousness. There are three approaches to the axiological question: I first-person contrast approach, II third-person contrast approach , and III reasoning approach.
The first point concerns moral value and possibly aesthetic value; the second point concerns cognitive value. The problem with this approach is that it is controversial whether our first-personal thoughts about the values of consciousness are reliable.
When reflecting on how we visually discriminate an object from others, for example, we are likely to think that if we lose perceptual consciousness, we cannot carry out the discrimination task. Dehaene and Naccache take this approach, arguing that consciousness enables durable and explicit information maintenance, novel combinations of operations, and intentional behavior.
Weiskrantz , chap. Kriegel compares our natural attitudes to conscious beings and non-conscious beings, and argues that consciousness confers dignity as a moral status on its possessors possibly with some other conditions. However, it may be objected that the apparent differences in values can be explained without appealing to consciousness Lau, ; see also Rosenthal, Hence, a challenge to the third-person contrast approach is to argue that the proposed difference in a type of value cannot be well explained without referring to consciousness.
The reasoning approach infers what values consciousness has from a given thesis about consciousness. The proponents of the attentional schema thesis that consciousness is an internal model of attention Graziano and Webb, can take it as a premise for reasoning and conclude that consciousness enables its possessor to control attention in proper manners.
This article proposes a map of consciousness studies, which consists of a systematic list of questions about consciousness and existing approaches to each question. I first address how IIT answers each fundamental question that I have listed.
In doing so, I point out several challenges to IIT. I then take the same procedure to examine GWT. I finally propose a way to clarify the relation between IIT and GWT with the help of the proposed map of consciousness studies.
The discussion is sketchy but still sufficient to demonstrate how the proposed map can be used to examine and compare theories of consciousness. Let us start with the definitional question. The intrinsic existence axiom states that consciousness exists independently from external observers, the composition axiom states that consciousness is structured, the information axiom states that each conscious experience is the particular way it is and thereby it differs from other possible conscious experiences, the integration axiom states that consciousness is unified, and the exclusion axiom states that consciousness is definite in content and spatiotemporal grain 9.
This indicates that the axioms are derived from phenomenological considerations, namely, by addressing the phenomenological question, in particular, the structure question of what invariant features consciousness has since the essential properties of consciousness are the invariant of consciousness.
This suggests that advocates of IIT answer the definitional question through tackling the structure question. This shows that they take the introspection approach to the structure question, rather than the observation approach and the reasoning approach, to derive the phenomenological axioms.
However, some philosophers cast doubt on the plausibility of the axioms as capturing the essential phenomenological features of consciousness Bayne, ; Pokropski, ; Miyahara and Witkowski, This demonstrates that the phenomenological axioms can be doubted and should not be taken to be immediately evident.
Thus, advocates of IIT must justify the phenomenological axioms, employing the other approaches if needed. Let us next move onto the ontological question. This statement is counted as the answer to the distribution question. IIT answers the mind—body question by stating that conscious experience is identical to an integrated informational structure of physical systems that instantiates the five postulates Tononi, , sec.
There is, however, no mention of how the identity claim is derived in any IIT literature. Article Google Scholar. Brain Stimul. Taschereau-Dumouchel, V. Natl Acad. USA , — Michel, M. Nature Hum. Download references. Technology Feature 09 NOV Research Highlight 29 OCT Article 10 NOV News 04 NOV Research Highlight 03 NOV News 22 OCT University of Washington UW.
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Credit: Sam Falconer. You have full access to this article via your institution. Download PDF. References 1. PubMed Article Google Scholar 2. PubMed Article Google Scholar 3. PubMed Article Google Scholar 4. PubMed Article Google Scholar 5. Article Google Scholar 6. PubMed Article Google Scholar 7. PubMed Article Google Scholar 8. PubMed Article Google Scholar 9.
Psychology When are masks most useful? Close banner Close. Email address Sign up. Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing. Search Search articles by subject, keyword or author. Tononi argues that the basic architecture of the computers we have today — made from networks of transistors — preclude the necessary level of information integration that is necessary for consciousness.
So even if they can be programmed to behave like a human, they would never have our rich internal life. He emphasises this is not just a question of computational power, or the kind of software that is used. It could even help us understand the ways we interact with each other.
Thomas Malone, director of the Massachusetts Institute of Technology's Center for Collective Intelligence and author of the book Superminds , has recently applied the theory to teams of people — in the laboratory, and in real-world, including the editors of Wikipedia entries. He has shown that the estimates of the integrated information shared by the team members could predict group performance on the various tasks. He cautions this is still very much speculation: we first need to be sure that integrated information is a sign of consciousness in the individual.
This piece contains original artwork by Emmanuel Lafont, an Argentinian-born visual artist currently working in Spain. His website is www. If you liked this story, sign up for the weekly bbc. In Depth Neuroscience. Are we close to solving the puzzle of consciousness?
Share using Email. By David Robson 27th March Can a lobster feel pain in the same way as you or I? Knowing what consciousness is, and how it came about, is crucial to understanding our place in the universe and what we do with our lives — Giulio Tononi. You might also like: Blindsight: the strangest form of consciousness What happens when anaesthesia fails What Peter Pan teaches us about memory and consciousness It begins with a set of axioms that define what consciousness actually is.
Drug-induced fantasies As a further comparison, the team also looked at participants under ketamine. As far as we can tell, almost all conscious experiences have their origin there. What is the crucial difference between these posterior regions and much of the prefrontal cortex, which does not directly contribute to subjective content?
The truth is that we do not know. Even so—and excitingly—a recent finding indicates that neuroscientists may be getting closer. An unmet clinical need exists for a device that reliably detects the presence or absence of consciousness in impaired or incapacitated individuals. During surgery, for example, patients are anesthetized to keep them immobile and their blood pressure stable and to eliminate pain and traumatic memories.
Unfortunately, this goal is not always met: every year hundreds of patients have some awareness under anesthesia. Another category of patients, who have severe brain injury because of accidents, infections or extreme intoxication, may live for years without being able to speak or respond to verbal requests. Establishing that they experience life is a grave challenge to the clinical arts.
Think of an astronaut adrift in space, listening to mission control's attempts to contact him. His damaged radio does not relay his voice, and he appears lost to the world. This is the forlorn situation of patients whose damaged brain will not let them communicate to the world—an extreme form of solitary confinement.
In the early s Giulio Tononi of the University of Wisconsin—Madison and Marcello Massimini, now at the University of Milan in Italy, pioneered a technique, called zap and zip, to probe whether someone is conscious or not. The perturbation, in turn, excited and inhibited the neurons' partner cells in connected regions, in a chain reverberating across the cortex, until the activity died out.
A network of electroencephalogram EEG sensors, positioned outside the skull, recorded these electrical signals.
As they unfolded over time, these traces, each corresponding to a specific location in the brain below the skull, yielded a movie. These unfolding records neither sketched a stereotypical pattern, nor were they completely random. Remarkably, the more predictable these waxing and waning rhythms were, the more likely the brain was unconscious. The zipping yielded an estimate of the complexity of the brain's response.
Massimini and Tononi tested this zap-and-zip measure on 48 patients who were brain-injured but responsive and awake, finding that in every case, the method confirmed the behavioral evidence for consciousness. The team then applied zap and zip to 81 patients who were minimally conscious or in a vegetative state.
For the former group, which showed some signs of nonreflexive behavior, the method correctly found 36 out of 38 patients to be conscious. It misdiagnosed two patients as unconscious. Of the 43 vegetative-state patients in which all bedside attempts to establish communication failed, 34 were labeled as unconscious, but nine were not.
Their brains responded similarly to those of conscious controls—implying that they were conscious yet unable to communicate with their loved ones. Ongoing studies seek to standardize and improve zap and zip for neurological patients and to extend it to psychiatric and pediatric patients.
Sooner or later scientists will discover the specific set of neural mechanisms that give rise to any one experience. Although these findings will have important clinical implications and may give succor to families and friends, they will not answer some fundamental questions: Why these neurons and not those? Why this particular frequency and not that? Indeed, the abiding mystery is how and why any highly organized piece of active matter gives rise to conscious sensation.
After all, the brain is like any other organ, subject to the same physical laws as the heart or the liver. What makes it different? What is it about the biophysics of a chunk of highly excitable brain matter that turns gray goo into the glorious surround sound and Technicolor that is the fabric of everyday experience? Ultimately what we need is a satisfying scientific theory of consciousness that predicts under which conditions any particular physical system—whether it is a complex circuit of neurons or silicon transistors—has experiences.
Furthermore, why does the quality of these experiences differ? Why does a clear blue sky feel so different from the screech of a badly tuned violin?
Do these differences in sensation have a function, and if so, what is it? Such a theory will allow us to infer which systems will experience anything. Absent a theory with testable predictions, any speculation about machine consciousness is based solely on our intuition, which the history of science has shown is not a reliable guide. Fierce debates have arisen around the two most popular theories of consciousness.
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