What are the different perspectives on consciousness

From the beetle in the box that no one has seen before

In the areas of science that deal with perception and consciousness, the fronts are currently shifting. Classically viewed as the subject of the humanities and social sciences, mental processes are increasingly attracting the interest of natural scientists. In the field of cognitive science (an interdisciplinary network of brain research, cognitive psychology, philosophy, neuroinformatics and artificial intelligence research), thinking, imagining, feeling and conscious experience are now considered to be empirically researchable and scientifically explainable.

In the classical philosophical systems of modern times, the problem of consciousness was treated with the greatest respect. Since Descartes, consciousness has been the defining characteristic of human nature. Due to the prevailing dualistic intuitions, it was believed that consciousness - like the spiritual in general - is inaccessible to any scientific explanation. The idea, which no longer seems completely utopian today, that artificial systems constructed by humans could one day also achieve a complexity sufficient for the attribution of consciousness, would have been perceived as absurd.

Even with the materialistic forefathers of modern medicine, consciousness and subjective experience were therefore excluded as scientifically inexplicable. A well-known example of this is Emil Du Bois-Reymond, physician and co-founder of modern electrophysiology, who represented this view in a lecture held in 1872 on the limits of scientific knowledge. Consciousness, he argued, could never be fully explained in terms of its material conditions. He closed his lecture with a Latin word: “Ignorabimus” - “we will not know”.

Today's representatives of cognitive science assess the situation much more optimistically. They classify consciousness and the phenomena associated with it as scientifically relevant objects of knowledge and as principally explainable empirically. Following this conviction, exactly 20 years ago a group of psychologists, philosophers and neuroscientists decided to found an international specialist society for scientific research into consciousness - the "ASSC" - which now organizes large conferences every year and works very successfully.

At the beginning of the 1990s, the Nobel Prize winner Francis Crick and the neuro-computer scientist Christof Koch formulated the point of view very pointedly that neurosciences should have priority in researching consciousness - only brain research is able to provide really convincing explanations in the long term. Such statements from brain research naturally had a provocative effect in other areas of science, which have been observing the progress of brain research with some skepticism since then.

Now - 25 years later - how can this announcement by Crick and Koch be assessed? How successful is brain research in this area? And can it remove the principal obstacles of which Du Bois-Reymond spoke?

The ideas developed since the early nineties differ fundamentally from classical views. Consciousness is now viewed as a class of processes that have a function for the organisms endowed with it and that arise within the framework of biological evolution. In addition, mind and consciousness are no longer seen as services that fundamentally differentiate humans from other living beings, but rather emphasis is placed on evolutionary continuity. The most important difference, however, is that the search for the biological roots of mental processes is now being carried out and a scientific theory of consciousness begins to develop.

A very successful strategy in cognitive science is to break down consciousness into various sub-functions - these can then be examined in a targeted manner. There is broad agreement that certain sub-functions must be present for consciousness to occur. For example, awareness requires a certain degree of alertness - the brain must have a sufficient level of activation and must not be in deep sleep or other states of low activation.

Since conscious mental states usually have a structured content, there must also be processes that embed information provided by the sensory organs into creative contexts and give them meaning. Without such a structure, our world of perception would remain an accumulation of meaningless patches of color, noises and smells, a confusing jumble of sensory impressions - comparable to what one sees when looking into a kaleidoscope.

Furthermore, a selection of content is necessary for awareness: For example, a selection of particularly relevant sensory data must take place. Even our everyday experience teaches that not all signals that flow to us from the environment reach our consciousness. This selection, which is mediated, among other things, by attention processes, leads to certain subsets of signals being transmitted and analyzed particularly efficiently in the brain. The deliberate processing of less relevant information, on the other hand, is blocked.

Furthermore, a functioning working memory, which enables the short-term storage of experience content, is probably indispensable for the occurrence of conscious mental states. After all, many theories of consciousness postulate that motivation and emotions also make decisive contributions to the development of consciousness.

The neurosciences have been extremely successful in investigating these sub-functions over the past few decades. Due to the rapid progress in the development of cell biological, neurophysiological and imaging methods, we now know very well the structure and functioning of the brain areas that are responsible for alertness, sensory processing, attention, memory, emotions and other functions essential for consciousness. At the moment, however, it is still less understood how all these sub-functions intertwine in order to contribute to the overall process of consciousness.

Indeed, brain research is increasingly focusing on the assumption that consciousness must be viewed as an integrative process. Many different brain regions are involved in the processes that contribute to consciousness. Obviously, an enormous number of nerve cells that are located in these regions must be coordinated in a flexible manner. Since the involved areas are sometimes far apart, large-scale functional couplings are necessary for the cooperation of the neurons. This dynamic coordination must be explained in order to understand how structurally organized perceptual impressions and ultimately also the unity of consciousness come about.

Brain research has made substantial progress on this issue as well. We now know that a time synchronization of the activities of different nerve cells serves to bring them together into effectively cooperating “teams”. It is very likely that a common rhythm in the activity of the nerve cells is the cause of the holistic nature of our perceptual impressions.

Crick and Koch were the first to suggest that the synchronization of nerve cells could play a crucial role in the emergence of consciousness. They postulated a close connection between synchronization and the contribution that neural signals make to consciousness. According to their hypothesis, only the signals from sufficiently synchronized neural "teams" should have enough penetrative power to reach consciousness via the path of working memory. A good body of research now suggests that Crick and Koch might be right in their conjecture.

With the help of electro- (EEG) or magnetoencephalography (MEG), one can examine neuronal synchronization processes that occur in connection with consciousness in test subjects. Experiments with ambiguous stimuli are extremely revealing. These are stimuli that allow two different interpretations, although they do not change themselves - such as the "Necker cube", which is drawn in two dimensions, but is perceived by us as three-dimensional from different perspectives. Despite always the same stimulus pattern, there is a "tilting" of perception and a change in the current content of consciousness. Current studies have succeeded in determining changes in neural synchronization in response to such stimuli and assigning them to specific sub-networks of the cerebral cortex.

The functional significance of these specific synchronization patterns is underpinned by attempts to influence the neural synchronization and thus to bring about changes in the content of consciousness. This can be achieved, for example, by neurostimulation with focal alternating electrical fields that are applied to the scalp through electrodes. Recently, this approach succeeded for the first time in modulating the synchronization between different brain areas and thereby changing the perception of an ambiguous stimulus.

While specific synchronization apparently serves to build up conscious mental states, consciousness is blocked by unspecific and overly synchronous neural rhythms. This has been shown in studies that analyze the synchronization of nerve cells under anesthesia. It has been shown, for example, that some frequently used anesthetics lead to unspecific and abnormally strong synchronization in large parts of the cerebral cortex. This very likely prevents sensory signals from being passed on in a targeted manner in the brain. In this way, conscious awareness is blocked - one of the main intended effects of anesthesia.

These and many other results make it very likely that specific synchronization processes are relevant for the emergence of consciousness. Neural synchronization is apparently suitable for mediating precisely coordinated interactions between different areas of the brain. The short-term build-up of system-wide “resonance” could possibly create something like a global “work space”, the states of which form the basis for our consciousness.

These new results of brain research and the rapid expansion of the knowledge arising here raise the question of the scope of neuroscientific explanations. Can brain research fully explain consciousness, self, and subjectivity? Neural processes are without question essential for the creation and structuring of consciousness. But are only neuroscientific approaches relevant for the explanation of consciousness? Or do other research approaches have to be included for a comprehensive theory?

The objection to a purely neuroscientific research program is that cognitive processes cannot be adequately described solely by reference to the subpersonal level. The fact that cognitive acts are performed by people is often overlooked in neuroscience, which likes to talk about the brain "recognizing" objects and the visual system "interpreting" scenes. It has been objected that this is an inadmissible use of language which simulates pseudo-solutions through category errors. It is not the brain that is “conscious”, but the whole cognitive system.

This leads to the question of how cognitive systems should be defined as carriers of consciousness at all. It is now often believed that a cognitive system includes the entire body, and not just the nervous system. This assumption makes sense because the physical constitution of an organism (its "embodiment"), which brings with it certain sensorimotor abilities and perspectives and certain environmental interactions, has a decisive influence on the cognitive inner workings. If one accepts this consideration, then consciousness could not simply be equated with the existence of certain brain states.

Some scientists - like the two philosophers Andy Clark and David Chalmers - even go a step further here. In their theory of the “extended mind” they also include environmental contexts in the definition of the cognitive system. In their view, the brain, body and local environment can only be viewed together and in their mutual coupling as “vehicles” of consciousness. In their opinion, states of the body and the environment can in principle have the same relevance as brain states for the explanation of consciousness. Purely neuroscientific explanations would necessarily fall short.

Another much-discussed objection to the neuroscientific approach relates to the problem of "qualia" - the subjective qualities of experience. There seems to be a fundamental gap in the explanation: Only knowing the brain states that accompany pain cannot tell what pain feels like. The problem seems to result from an unbridgeable gap between the objective and the subjective, from a lack of translatability of the experience perspective of the first person into the third person perspective with which science inevitably operates. So there could be irreducibly subjective characteristics of consciousness that a scientific theory cannot depict. This problem would not only arise for neuroscientific attempts at explanation, but for every empirically oriented theory of consciousness.

Whether brain research reaches a fundamental limit here depends above all on how exactly the term qualia is defined. A decisive feature of qualia, it is often discussed, is its privacy - the subjective qualities of experiences are only known to the person who is currently experiencing them. However, the strict privacy of qualia can be contested with good philosophical arguments. One of the most famous was formulated by the philosopher Ludwig Wittgenstein, who compared Qualia to a beetle in a box that each of us carries with us. If you never show these "bugs" to each other - so Wittgenstein - it is irrelevant whether there is anything in the boxes at all. In his view, there can be no meaningful concept of consciousness that assumes complete privacy of qualia.

Whatever the question of the solvability of the qualia problem - in fact, the other arguments mentioned already suggest that brain research alone cannot provide a complete theory of consciousness. Neuroscience studies important structural and functional components of consciousness, but other levels of description must be included here. The neurobiological analysis must remain linked to a description of the dynamics of the “extended cognitive system” in its entirety. This implies that neuroscience cannot provide an explanation of the mental on its own, but must seek cooperation with other sciences. The hegemonic claims of brain research towards the humanities and social sciences could hardly be justified here.

In the opinion of the author, however, it by no means follows from the considerations made here that consciousness and subjectivity are fundamentally beyond scientific theory formation. The methodological and substantive advances in cognitive science lead us to expect that it will not stop at "ignorabimus". For the majority of researchers, the intuition formulated by Du Bois-Reymond is losing ground that there is an insurmountable explanation gap between the mental and the physical. If consciousness is not something intangible and metaphysical, but a class of phenomena that can be empirically investigated, then it could be that science can elucidate its mechanisms in the long term and even implement it - at least partially - in artificial systems.

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