Theory of Consciousness

See also

Cognitive Theories of Consciousness; Folk Theories of Consciousness; Functions of Consciousness; History of Philosophical Theories of Consciousness; Intentionality and Consciousness; Language and Consciousness

Summary

What should we expect from a neural theory of consciousness? One thing we should not ask for is that the theory produce consciousness. After all, a theory of hurricanes is not itself windy. Rather, a useful theory should help move from establishing correlations between brain activity and conscious experience toward developing explanations that link features of brain activity with features of conscious phenomenology, as well as accounting for the relevant experimental evidence. Because consciousness is a rich biological phenomenon, the theories surveyed in this article vary in emphasis, level of abstraction, and the extent to which they provide satisfying explanations of conscious phenomena. At present, no single effort accounts for all the evidence, but we have seen marked progress in the last few decades.

The future of scientific theories of consciousness

It is clear, then, that proper scientific theories of consciousness are those that specify which functions are necessary for consciousness to arise. A true scientific theory will say how functions such as attention, working memory and decision making interact and come together to form a conscious experience. Any such theory will need to have clear and testable predictions that can in principle be verified or falsified. Most importantly, such theories will not claim that consciousness is a unique brain state that occurs independently of function; instead, the focus will be placed on the functions themselves and how they interact and come together to form consciousness.

There are several theorists who have already realized the need for functions in developing theories of consciousness. Dehaene and colleagues [16] have put forth a global neuronal workspace model that claims consciousness is defined by the orientation of top-down attention, long-distance feedback loops that extend into parietofrontal networks, and conscious reportability. Similarly, Kouider and colleagues [27] have discussed at great length how information that is in consciousness relies on a hierarchy of representational levels. Under this view, each level corresponds to different cognitive mechanisms responsible for different units of representation.

It is important to stress that both of these theories are merely the beginning, rather than the end, of the study of consciousness. There is still much work to be done in regards to how these functions and mechanisms interact. In Dehaene et al.’s theory, for example, a more thorough and specific understanding of the type of parietofrontal activation [16] and how it relates to the formation of memories and decisions is still necessary. The upshot of function-based theories is that they make claims about consciousness that can be tested and examined scientifically.

Although there are certainly those who disagree with the specifics of the theories put forth by Dehaene et al. and Kouider et al. [4–14], these are disagreements that can eventually be settled through more rigorous examination and testing. The same cannot be said of theories that maintaining that consciousness occurs independent of function. As the perfect experiment illustrates, such theories inherently prevent any future avenue for scientific research.

In the present article, we first overview the precursors that allowed the development of cognitive theories of consciousness, and in particular we consider the notions of attention, working-memory, modularity, and the distinction between automatic and controlled processes. Then we present a selection of influential contemporary accounts of consciousness on the basis of three themes: consciousness results from specific architectural elements within the cognitive system (the theories by Baars, Prinz, Tononi); some features of consciousness are in fact illusory (the theories by Dennett and Wegner); and consciousness is about learning (the theories by O’Regan and Noë, Cleeremans, Lau). We conclude this article by considering that these cognitive theories have to set a bridge between the philosophical hard problem of consciousness and neurobiological approaches.

Cognitive Theories

Many people have conjectured that consciousness might be linked to cognitive characteristics, such as emotions, imagination and a model of the self. If consciousness depends on functions at the cognitive level, then it should be possible to realize it on any piece of hardware that is capable of carrying out the appropriate processing. One example of a cognitive theory of consciousness is the axiomatic theory of Igor Aleksander, which claims that imagination, emotion, depiction, volition and attention are minimally necessary for consciousness, and any natural or artificial system that implements these axioms is judged to be conscious according to this theory. Global workspace theory is another cognitive architecture that can be implemented on many different types of hardware, and Thomas Metzinger's phenomenal self model and constraints on conscious experience are also largely independent of the physical system.

People’s folk theory of consciousness encompasses three prototypes of conscious mental functioning: monitoring (awareness), choice, and subjective experience. All three are embedded in a broader folk theory of mind and thus closely linked to the concept of intentionality, action explanation, and a conception of free will. At least some of the prototypes of consciousness play a critical role in the assignment of personhood and responsibility. Recent discussions question the viability of folk conceptions of consciousness in light of work on the unconscious and neuroscience. Thus far this work appears to complement folk conceptions without contradicting them.

Other theories

Many other theories of consciousness have positive implications for the possibility of creating consciousness in artificial systems. To begin with, the pantheist claim that all matter is conscious to some degree suggests that computers and robots are conscious even when they are switched off. David Rosenthal's claim that consciousness depends on a higher-order thought about another mental state is not linked to any particular implementation, and a number of connections have been made between consciousness and virtual machines that can run on any type of hardware. Some researchers have claimed that inner speech helps to constitute our sense of self and agency and may be important to consciousness as well. If this is the case, it might be possible to use the work on language acquisition in AI to develop conscious systems.

Abstract

Various theories for the neural basis of consciousness have been proposed, suggesting a diversity of neural signs and mechanisms. We ask to what extent this diversity is real, or whether many theories share the same basic ideas with a potential for convergence towards a more unified theory of the neural basis of consciousness. For that purpose, we review and compare the various neural signs, measures, and mechanisms proposed in the different theories. We demonstrate that different theories focus on neural signs and measures of distinct aspects of neural activity including stimulus-related, prestimulus, and resting state activity as well as on distinct features of consciousness. Therefore, the various mechanisms proposed in the different theories may, in part, complement each other. Together, we provide insight into the shared basis and convergences (and, in part, discrepancies) of the different theories of consciousness. We conclude that the different theories concern distinct aspects of both neural activity and consciousness which, as we suppose, may be integrated and nested within the brain’s overall temporo-spatial dynamics.