Consciousness is an individual’s state of awareness of their environment, thoughts, feelings, or sensations; in order to experience consciousness, one must be both awake and aware.
Trace the history of the study of consciousness
- Philosophers since the time of Descartes and Locke have struggled to comprehend the nature of consciousness and pin down its essential properties.
- The study of consciousness helps scientists shed light on the inner workings of psychology and neuroscience. Scientists who study consciousness examine the relationship between stated perception and neural activity.
- The majority of experimental studies assess consciousness by asking human subjects for a verbal report of their experiences and then comparing their answers with the corresponding neural activity.
- While primary sensory areas of the brain are often involved in perception, it is the higher brain areas such as the primary cortex that are required for consciousness to occur.
- Issues of interest in consciousness research include phenomena such as perception, subliminal perception, blindsight, anosognosia, brainwaves during sleep, and altered states of consciousness produced by psychoactive drugs or spiritual or meditative techniques.
- anosognosia: The inability of a person to recognize his or her own illness or handicap.
- subliminal perception: Perception that is below the threshold of consciousness.
- blindsight: The responsivity shown by some blind or partially blind people to visual stimuli of which they are not consciously aware.
Consciousness is the quality or state of being aware of an external object or something within oneself, such as thoughts, feelings, memories, or sensations. It has also been defined in the following ways: sentience, awareness, subjectivity, the ability to experience or to feel, wakefulness, having a sense of selfhood, and the executive-control system of the mind. At one time, consciousness was viewed with skepticism by many scientists, but in recent years, it has become a significant topic of research in psychology and neuroscience.
Philosophy of Consciousness
Despite the difficulty in coming to a definition, many philosophers believe that there is a broadly shared underlying intuition about what consciousness is. Philosophers since the time of Descartes and Locke have struggled to comprehend the nature of consciousness and pin down its essential properties. Issues of concern in the philosophy of consciousness include the following: whether consciousness can ever be explained mechanistically; whether non-human consciousness exists, and if so, how it can be recognized; how consciousness relates to language; whether consciousness can be understood in a way that does not require a dualistic distinction between mental and physical states or properties; and whether it may ever be possible for computers or robots to be conscious.
The Mind-Body Problem
The mind-body problem is essentially the problem of consciousness; roughly speaking, it is the question of how mental experiences arise from a physical entity. How are our mental states, beliefs, actions, and thinking related to our physical states, bodily functions, and external events, given that the body is physical and the mind is non-physical?
The first and most important philosopher to address this conundrum was René Descartes in the 17th century, and his answer was termed Cartesian dualism. The explanation behind Cartesian dualism is that consciousness resides within an immaterial domain he called res cogitans (the realm of thought), in contrast to the domain of material things, which he called res extensa (the realm of extension). He suggested that the interaction between these two domains occurs inside the brain. He further suggested the pineal glad as the point of interaction, but was later challenged several times on this claim. These challenges sparked some key initial research on consciousness, which we will discuss shortly.
Early Ideas on Consciousness
For over 2000 years, questions surrounding human consciousness—such as how the everyday inner workings of our brains give rise to a single cohesive reality and a sense of an individual self—have been baffling philosophers from Plato to Descartes. Descartes, as previously mentioned, is noted for his dualist theory of consciousness, in which the physical body is separate from the immaterial mind. He also gave us the most famous summary of human consciousness: “I think, therefore I am.”
The historical materialism of Karl Marx rejects the mind-body dichotomy, and holds that consciousness is engendered by the material contingencies of one’s environment. John Locke, another early philosopher, claimed that consciousness, and therefore personal identity, are independent of all substances. He pointed out that there is no reason to assume that consciousness is tied to any particular body or mind, or that consciousness cannot be transferred from one body or mind to another.
American psychologist William James compared consciousness to a stream—unbroken and continuous despite constant shifts and changes. While the focus of much of the research in psychology shifted to purely observable behaviors during the first half of the twentieth century, research on human consciousness has grown tremendously since the 1950s.
Current Research on Consciousness
Today, the primary focus of consciousness research is on understanding what consciousness means both biologically and psychologically. It questions what it means for information to be present in consciousness, and seeks to determine the neural and psychological correlates of consciousness. Issues of interest include phenomena such as perception, subliminal perception, blindsight, anosognosia, brainwaves during sleep, and altered states of consciousness produced by psychoactive drugs or spiritual or meditative techniques.
The majority of experimental studies assess consciousness by asking human subjects for a verbal report of their experiences. However, in order to confirm the significance of these verbal reports, scientists must compare them to the activity that simultaneously takes place in the brain—that is, they must look for the neural correlates of consciousness. The hope is to find that observable activity in a particular part of the brain, or a particular pattern of global brain activity, will be strongly predictive of conscious awareness. Several brain-imaging techniques, such as EEG and fMRI scans, have been used for physical measures of brain activity in these studies.
Higher brain areas are more widely accepted as necessary for consciousness to occur, especially the prefrontal cortex, which is involved in a range of higher cognitive functions collectively known as executive functions.
A History of Theories of Consciousness
Theories of consciousness include developmental, cultural, neural, computational, and moral perspectives.
Critique the major theories about human consciousness
- First appearing in the historical records of the ancient Mayan and Incan civilizations, various theories of multiple levels of consciousness have pervaded spiritual, psychological, medical, and moral speculations in both Eastern and Western cultures.
- The Ancient Mayans were among the first to propose an organized sense of each level of consciousness, its purpose, and its temporal connection to humankind.
- Sigmund Freud divided human consciousness into three levels of awareness: the conscious, preconscious, and unconscious.
- Modern psychological approaches to understanding consciousness include developmental, social, and neuropsychological; each contribute a different understanding of what consciousness might be.
- consciousness: The state of being aware; awareness to both internal and external stimuli.
- Sigmund Freud: (1856–1939) An Austrian neurologist who became known as the founding father of psychoanalysis.
Historical Theories of Consciousness
Mayan and Incan Theories of Consciousness
First appearing in the historical records of the ancient Mayan and Incan civilizations, various theories of multiple levels of consciousness have pervaded spiritual, psychological, medical, and moral speculations in both Eastern and Western cultures. Consciousness can be defined as human awareness to both internal and external stimuli. Because of occasional and sometimes substantial overlap between hypotheses, there have recently been attempts to combine perspectives to form new models that integrate components of separate viewpoints.
The Ancient Mayans were among the first to propose an organized sense of each level of consciousness, its purpose, and its temporal connection to humankind. Because consciousness incorporates stimuli from the environment as well as internal stimuli, the Mayans believed it to be the most basic form of existence, capable of evolution. The Incas, however, considered consciousness a progression not only of awareness but of concern for others as well.
John Locke on Consciousness
John Locke, a 17th-century philosopher, was one of the first to speak and write on consciousness. He believed that our identity was tied to our consciousness, which he essentially defined as what passes through a man’s mind, or memories. He also asserted that our consciousness is not tied to our physical bodies, and that it can survive even after our physical bodies die. In fact, Locke held that consciousness could be transferred from one soul to another.
René Descartes on Consciousness
René Descartes also addressed the idea of consciousness in the 17th century. He set out to answer the question of how it is possible that our consciousness, a non-physical thing, can come from our bodies, a physical thing. The explanation he came up with was called Cartesian dualism; in short, consciousness resides within an immaterial domain he called res cogitans (the realm of thought), in contrast to the domain of material things, which he called res extensa (the realm of extension). He suggested that the interaction between these two domains occurs inside the brain.
Sigmund Freud on Consciousness
While Eastern perspectives on consciousness have remained relatively stable over the centuries, fluctuations in theory have come to define the Western perspective. One of the most popular Western theories is that of Sigmund Freud, medical doctor and father of psychoanalytic theory. Freud divided human consciousness into three levels of awareness: the conscious, preconscious, and unconscious. Each of these levels corresponds and overlaps with Freud’s ideas of the id, ego, and superego. The conscious level consists of all the things we are aware of, including things we know about ourselves and our surroundings. The preconscious consists of things we could pay conscious attention to if we so desired, and is where many memories are stored for easy retrieval. Freud saw the preconscious as comprised of thoughts that are unconscious at the particular moment in question, but that are not repressed and are therefore available for recall and easily capable of becoming conscious (for example, the tip-of-the-tongue effect). The unconscious consists of things that are outside of conscious awareness, including many memories, thoughts, and urges of which we are not aware. Much of what is stored in the unconscious is thought to be unpleasant or conflicting; for example, sexual impulses that are deemed unacceptable. While these elements are stored out of our awareness, they are nevertheless thought to influence our behavior.
Modern Theories of Consciousness
While Freud’s theory remains one of the best known, various schools in the field of psychology have developed their own perspectives, which we will explore below. It is important to note that these perspectives are not necessarily mutually exclusive, just different approaches to the same questions.
Developmental Psychology on Consciousness
Developmental psychologists view consciousness not as a single entity, but as a developmental process with potential higher stages of cognitive, moral, and spiritual quality. They posit that consciousness changes over time, in quality and in degree: an infant’s consciousness is qualitatively different than a toddler’s, a teenager’s, or an adult’s. Abnormal development also affects consciousness, as do mental illnesses.
Social Psychology on Consciousness
Social psychologists view consciousness as a product of cultural influence having little to do with the individual. For instance, because different cultures speak different languages, they also codify reality differently. That difference in codification leads to differences in the experience of reality, and therefore of consciousness. Language is the main mechanism for transmitting a mode of consciousness, and an analysis of language can to some extent reveal the mentality of people who speak that language.
Neuropsychology on Consciousness
Neuropsychologists view consciousness as ingrained in neural systems and organic brain structures. A major part of the modern scientific literature on consciousness consists of studies that examine the relationship between the experiences reported by subjects and the activity that simultaneously takes place in their brains—that is, studies of the neural correlates of consciousness. The hope is to find activity in a particular part of the brain, or a particular pattern of global brain activity, that will be strongly predictive of conscious awareness. Several brain-imaging techniques, such as EEG and fMRI, have been used for physical measures of brain activity in these studies.
Neural Underpinnings of Consciousness
The neural correlates of consciousness (NCC) refer to the relationship between the experiences reported by subjects and the activity that simultaneously takes place in their brains.
Analyze the neural mechanisms underpinning conscious awareness
- Consciousness is the awareness of the self in space and time. Researchers attempt to study states of human consciousness and differences in perception in order to understand how the body works to produce conscious awareness.
- Neural correlates of consciousness (NCC) are sets of neurons and series of events necessary for conscious perception. Neural correlates in the brain have been found to be both redundant and parallel, which makes pinpointing brain activity difficult for researchers.
- Consciousness varies in both arousal and content. We have two types of conscious experience: phenomenal, or in the moment, and access, which recalls experiences from memory.
- Neural correlates of consciousness are studied using fMRI and EEG scans, which attempt to locate brain activity. The most popular stimuli for these studies has become visual tests as they are easily recorded and manipulated.
- arousal: A physiological and psychological state of being awake or reactive to stimuli, including elevated heart rate and blood pressure, and a condition of sensory alertness, mobility, and readiness to respond.
- consciousness: The state of being aware; awareness to both internal and external stimuli.
Consciousness is the awareness of the self, the environment, and the relationship between these two distinct worlds. From ancient philosophers to modern-day scientists, many people have struggled to understand, research, and document the processes involved in human consciousness. Thanks in large part to advances in medicine, science, and psychology, we have learned much about how states of consciousness are created. Current research studies the neural correlates of consciousness by examining experiences reported by subjects and recording the simultaneous activity that takes place in their brains. Researchers continue to search for brain activity or global brain patterns that can be predictive of conscious awareness.
Neural Correlates of Consciousness (NCC)
The neural correlates of consciousness (NCC) refer to the relationship between the experiences reported by subjects and the activity that simultaneously takes place in their brains. The physical world is perceived by human consciousness through the senses, which funnel stimuli and information into the central nervous system, and eventually the brain. The brain is the major organ implicated in turning physical stimuli into thoughts and actions. The study of NCC seeks to link objective, observable, neural activity to subjective, unobservable, conscious phenomena. While discovering and characterizing neural correlates cannot offer its own theory of consciousness, the data and findings may one day lead to such a discovery.
Neural networks have been found to have a large amount of redundancy and parallelism, such that activity in one set of neurons cannot necessarily be said to correlate with the same perception over time. Scientists believe it may be the case that every phenomenal, subjective state has its own neural correlate. Continued advances in the ability to stimulate or induce activity in certain brain regions or sets of neural networks will help scientists answer ever more complicated questions about the characteristics and commonalities among neural correlates.
Neurobiology and Consciousness
The science of consciousness sets out to explain the precise relationship between subjective mental states and brain states, the relationship between the conscious mind and the electro-chemical interactions in the body. Progress in this arena has come from focusing on the body rather than the mind. In this context, the neuronal correlates of consciousness may be viewed as its causes, and consciousness may be thought of as a state-dependent property of some complex, adaptive, and highly interconnected biological system.
Most neurobiologists assume that the variables giving rise to consciousness are to be found at the neuronal level, governed by classical physics. More than ever before, neuroscientists are able to manipulate neurons
using methods from molecular biology combined with state-of-the-art optical tools (e.g., Adamantidis et al., 2007). Neuronal analysis and brain imaging techniques have become so fine-grained that a rational understanding of consciousness is within reach.
Dimensions of Neural Consciousness: Arousal and Content
Neuronal consciousness is often described as involving two distinct dimensions: arousal and content. In order for the brain to be conscious of any type of content, it must be in a high state of arousal. While awake and dreaming states are fundamentally different states of consciousness, they are both high-arousal, and thus allow for perception. Sleep is just one of the many types of consciousness we can experience and comprises several states of consciousness itself. Consciousness can also be phenomenal, such as our experiences in real time, or access, such as recalling a state of being or feeling.
Brain Areas Implicated in Consciousness
Another idea that has drawn attention for several decades is that consciousness is associated with high-frequency (gamma band) oscillations in brain activity. This idea arose from proposals in the 1980s, by Christof von der Malsburg and Wolf Singer, that gamma oscillations may link information represented in different parts of the brain into a unified experience.
Several studies have demonstrated that activity in primary sensory areas of the brain is not sufficient to produce consciousness: it is possible for subjects to report a lack of awareness even when areas such as the primary visual cortex show clear electrical responses to a stimulus. Higher brain areas are seen as more promising, especially the prefrontal cortex, which is involved in a range of executive (higher-order) functions. There is substantial evidence that a “top-down” flow of neural activity (i.e., activity propagating from the frontal cortex to sensory areas) is more predictive of consciousness than a “bottom-up” flow of activity. The prefrontal cortex is not the only candidate area, however: studies have shown that visually responsive neurons in parts of the temporal lobe reflect the visual perception in the situation when conflicting visual images are presented to different eyes.
Brain Imaging and Consciousness
One popular theory implicates different patterns of brain waves in producing different states of consciousness. Researchers can record brain waves, or tracings of electrical activity within the brain, using an electroencephalograph (EEG) and placing electrodes on the scalp. The four types of brain waves (alpha, beta, theta, and delta) each correspond with one mental state (relaxed, alert, lightly asleep, and deeply asleep, respectively).
Functional magnetic resonance imaging (fMRI) scans, can also be used to measure physical activity in the brain that correlates with different conscious states and perceptions. The ease in which visual perceptions can be manipulated in time and space has made visual studies, such as the Necker cube, one of the most preferred modalities for studying the neural correlates of consciousness. These studies take a seemingly simple and unambiguous visual stimulus and record differences in its subjective perception by a study participant. The cube, for instance, is 12 basic lines that can be interpreted in two different depths, creating a visual illusion. Scientists are interested in locating which neural correlates lead to differing mental interpretations.