What is consciousness?If you're reading these words, there can be no doubt that something called consciousness exists, and that you have it! But the exact nature of consciousness, its relationship to the brain, and whether it can ever be explained in neurobiological terms are the subject of considerable debate.

Grafikerin: Meike Ufer
Was ist Bewusstsein?
Author: Ulrich Pontes

If you're reading these words, there can be no doubt that something called consciousness exists, and that you have it! But the exact nature of consciousness, its relationship to the brain, and whether it can ever be explained in neurobiological terms are the subject of considerable debate.

Scientific support: Prof. Dr. Georg Northoff

Published: 27.08.2013

At a glance
  • The moment we think about something, we do so consciously: this means that the existence of consciousness can't be doubted or argued away. This observation was captured by Descartes in the famous phrase: "I think, therefore, I am."
  • Consciousness is the quality that distinguishes a state of being awake from that of a coma. But to speak of consciousness is always to speak of consciousness ofsomething. And many more distinctions can be made, to the extent that we must wonder whether there a single phenomenon called consciousness really exists.
  • A popular explanatory model is the "Global Workspace Theory," which considers consciousness as a sort of central place for carrying out activities: What happens there is accessible to the many diverse, largely unconscious processes which occur in the brain.
  • For philosophers consciousness is captured by the ancient "body-soul" problem: What connects the mental and physical worlds, which apparently function according to entirely different rules?
  • Neuroscientists are increasingly attempting to cope with the theme. The extent to which consciousness can be reduced to purely biological and physical phenomena, however, remains a matter of debate.
Awareness and consciousness

In our everyday experience, awareness and consciousness are generally directed at the same object. However, they are not the same and do not always automatically overlap. This is demonstrated in experiments that fool the optical system, for example by presenting the left and right eyes with different images. This procedure shows that awareness can be manipulated – so that although both images reach the retina, a subject is never aware of one of them. Independently of this pheomenon, a person's awareness can also be directed by instructions. Using this method, Masataka Watanabe's group from the Max Planck Institute for Biological Cybernetics in Tübigen have shown that the activity of the primary visual cortex is dependent on awareness, but not on whether a particular pattern is consciously seen or not. (Abstract).

The flow of consciousness

In his book Principles of Psychology, the American Psychologist and Philosopher William James (1842-1910) characterized consciousness as something continuous but not constructed of individual components: "It flows." This led him to characterize all of our changing thoughts, perceptions, emotions and feelings with the metaphor of a flow or stream – "the stream of consciousness" – which he regarded as the "ultimate fact for psychology." Later this concept led to the development of the theory of the global workspace.

There is no consensus among experts, however, that consciousness really exists: British researcher and writer Susan Blackmore criticized this concept as an illusion.

This didn't prevent James' term from establishing itself, particularly in the field of literature. The "stream of consciousness" form of narrative attempts to capture a rather direct picture of this flow – including wild associations and leaps in thinking, without interruption by punctuation. James Joyce's famous novel Ulyssesis a prime example.

There is probably no phenomenon in the universe to which we feel more directly connected than our own consciousness. In its absence, our sense of humanity and individuality would be unthinkable, as would most of our complex interactions with our surroundings. As you read this text, are you being distracted by the associations it calls to mind, or other factors? Anything that you sense is happening is taking place on the stage of your unique individual consciousness.

Nothing in the world can be as certain as the fact that we are conscious, from the instant we think about it: "I think; therefore, I am."  René Descartes constructed an entire philosophy around this fundamental principle. Everything else may be cast into doubt: sensory impressions may be hallucinations, our convictions illusions, and our entire surroundings a vast conspiracy – the "Matrix" films created an opulent story out of ideas that Descartes considered long ago. But consciousness remains a fact.

"One of the most puzzling features of the universe"

In public lectures the US philosopher John Searles has repeatedly called consciousness "the most important aspect of our lives." His argument is pointedly clear: Consciousness is an essential precondition for attaching meaning to the things in our lives. And if nothing can be important to us without consciousness, then consciousness must be the most important thing of all.

Although we take consciousness for granted as an everyday experience, a closer look reveals the high complexity of this phenomenon. Neurobiologist Christof Koch, who has conducted research into consciousness for many years, calls it "one of the most puzzling features of the universe." No wonder the problem has been a bane to philosophers for centuries (Das Rätsel Bewusstsein). Today there is no commonly accepted definition of what it means, and even in daily use its meaning is opaque. Neurophilosopher Thomas Metzinger from the University of Mainz had to provide five different definitions of "consciousness" for his entry in the "Enzykolpädie Philosophie."

For example, the term can be used to declare whether someone is (fully) conscious or not – a person might be asleep (Die Nachtseite des Bewusstseins), under total anesthesia  (Was geschieht bei der Narkose?) or in a coma  (Tennisspielen im Wachkoma). These are states that can be objectively defined and – at least partly – explained in neurobiological terms. Things get trickier when it comes to "being conscious" of a thing, another person, a fact, or any object whatsoever: being conscious of a mistake I have made, or an unpleasant odor, is a highly subjective mental process. It is something that takes place only in my head, and others can only become aware of it when I communicate the experience – either consciously or "unconsciously", such as through a facial expression.

A dance on the stage of subjective experience

Awake consciousness, this dance on the internal stage of subjective experience, begins upon awakening and continues without a pause until we go to sleep. It is hard to imagine, at least, being awake without some conscious awareness of a thought, a feeling, a sensory impression or an activity. This means that all thoughts, feelings, impressions and activity are somehow dependent on consciousness. But in fact, psychological and neurobiological research paint a different picture: many of these processes take place on an unconscious level in our minds, and because of this they can be much faster and more effective. (See also the articles Wenn ich ein Zombie wäre, Wie unser Unbewusstes für uns entscheidet, Was sind Emotionen?)

Even more distinctions can be made: consciousness is not the same as attention (see the box "Attention and consciousness"). Consciousness can be outwardly directed, toward objects of perception, or can point inward toward an introspective awareness of our own mental states. The latter shows why consciousness is sometimes described as a higher state or metaprocess: if I am annoyed by another driver on the road and curse, I can simultaneously observe and reflect on this behavior on a metalevel – and maybe even decide that my expression of rage wasn't appropriate, given the presence of my mother-in-law in the shotgun seat.

It is through conscious reflection about oneself that a person develops an identity and self-awareness, in the manner that philosophers have continually searched for answers. But this should be distinguished from the type of self-consciousness that is normally thought of, in daily language: the personality of someone who is confident of himself and his abilities.

The theory of the global workspace

Philosopher Ned Block of New York University distinguishes two types of consciousness: first, "phenomenal consciousness" – the type of subjective experience we have when appreciating a flower or enjoy a touch – and "access consciousness," which refers to information that is within the reach of a person's mental and behavioral control. The latter concept can be directly associated with the "global workplace" model of consciousness. A metaphor would be a theater stage illuminated by a spotlight: only things which take place on the stage can be heard and seen by a public sitting in the dark (akin to the many unconscious processes which occur in the brain) and are accessible as information.

All of the qualifiers surrounding the term have caused some philosophers to wonder whether consciousness is in fact a single, unified phenomenon or rather a collective term for diverse things. Metzinger's encyclopedia article suggests this as well, pointing out that many languages do not have a single word that clusters all of these meanings. This could be a result of the fact that consciousness has long been absent from the radar of serious scientific research. Neuroscience textbooks can be found that – in spite of being hundreds of pages long – don't even display the word in their index. John Searle cites a neuroscientist who told him: "Of course you can carry out research on consciousness – just be sure you have an open-ended contract!"

Although the eternal soul is passé, questions of belief linger

Even without considering the difficult reputation the field has gained in some circles, consciousness remains a difficult topic. In searching for consciousness, the age-old "body-soul" problem becomes crystallized: What is the connection between the physical and mental worlds? From an objective point of view, how much reality reaches this mental world? In science one truly promotes the concept of a soul that can exist independently of a body – at least since the death of John Eccles in 1997 (John Eccles – Über den Spalt hinweg) That the physical-neuronal processes in the brain are an essential foundation of its mental processes is considered a proven fact.

Whether this means that such processes determine a mental life is another question entirely. Is consciousness merely a purely biological process like everything else that happens in our bodies – albeit a particularly difficult subject for research because its content is a subjective phenomenon? In other words, can it in principle be reduced to complex physical phenomena? For the moment the answer remains a matter of belief, as the empirical scientist Christof Koch elegantly points out: "It is not at all clear whether two brains that were identical, from a physical point of view, would automatically exhibit the same state of consciousness."

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