Consciousness, Levels of

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Consciousness, levels of


The everyday meaning of the word "consciousness" corresponds fairly closely to how most psychologists use the term. To be conscious is to be aware.


Most of the time, we are aware of whatever activity happens to be at the center of our current attentional focus. For example, in order to read this sentence the readers need to focus their attention on the appropriate line on the page, and concentrate on extracting meaning from what they are reading. Such conscious attention is, however, very selective. Research has demonstrated that a great deal of our mental activity is performed outside of conscious awareness. Consciousness is like the tip of an iceberg. It allows us to exert purposeful control over our current activities, and to communicate our mental states to others. We selectively attend to only a small fraction of the stimulation to which we are constantly exposed. We ignore many sources of external information, but can be made instantly aware of them. Upon reflection, it is obvious that we are operating at various levels of consciousness throughout the day. Do students daydream in class, and later wonder what the teacher said? When people brush their teeth, are they thinking about how clean they are getting them? There are a variety of states or levels of consciousness that have been studied extensively by psychologists. A few of them are described below.


Perhaps the most frequent and conspicuous altered state of consciousness is experienced during sleep. Sleep is typically studied by means of an electroencephalograph. It produces a visual record (called an EEG) of the changes in electrical activity in the brain that occur during sleep. Changes in muscle activity and eye movements are also monitored. There are four major stages of sleep that are distinguished from one another on the basis of the electrical activity associated with each. There is also a distinctive fifth stage, known as REM (rapid eye movement) sleep. During this phase the brain's electrical activity is similar to that of the waking state. The sleeper's eyes dart about rapidly, even though the lids remain closed. Apart from the occasional twitch, there is a total suppression of muscle movement. The sleeper is essentially paralyzed. Because the brain's motor cortex is active during this stage, REM sleep is sometimes referred to as "paradoxical sleep." There is considerable internal activity, but an external calmness. REM sleep is the stage during which almost all dreaming occurs. REM sleep is usually accompanied by genital arousal in both males and females, although such arousal is unrelated to dream content. Regardless of the stage of sleep, there is no evidence that any substantive learning can take place during sleep. Despite extravagant claims, listening to a foreign language while sleeping is not going to make someone bilingual.


Most of us have seen Hollywood movies in which a hypnotist puts somebody in a trance and then ostensibly induces them to perform silly and sometimes dangerous activities. There are reports of criminal investigations having been assisted by witnesses whose memories have been hypnotically enhanced. "Age regression" demonstrations show hypnotized subjects apparently reliving experiences from their childhood. Are these memories accurate? Does hypnotism produce an altered state of consciousness? Can hypnosis cause people to act against their will?

There are two competing explanations of what goes on during hypnosis. The social-cognitive approach views hypnosis as a social phenomenon. According to this perspective, hypnosis is not a unique physiological state and the behaviors produced by hypnosis can also be produced by other means. Hypnotized people are simply in a heightened state of suggestibility. Most people know what is supposed to happen during a hypnosis session. If the hypnotist's suggestions are believed to be irresistible, then people will comply with them. It's not that people are being deliberately deceptive. Their behaviors are genuine enough but they reflect beliefs about hypnosis and the role of hypnotized subjects, rather than the skills of the hypnotist or an altered state of consciousness.

The dissociation approach views hypnosis as a procedure that produces a split between two basic functions of consciousness—the executive function that we use for controlling our own behavior, and the monitoring function that is used for observing it. Hypnosis is assumed to disconnect these two components of consciousness, thereby preventing hypnotic experiences from entering normal consciousness. The two approaches are not necessarily contradictory. Certainly there is abundant evidence that social scripts play a role in many hypnotically induced behaviors. Numerous studies have shown that normal subjects who are asked to pretend to be hypnotized produce behaviors that are indistinguishable from those of hypnotized subjects. In another study, hypnotized subjects were given what they were told was a blank piece of paper. In reality, the number 8 was written on it. After hypnosis, those who reported that the paper was blank were told that only fakers would say that. They were then asked to draw what had been on the paper. Almost all drew the number 8. As far as hypnotically enhanced memories are concerned, such testimony is rarely admissible in court. The problem is that hypnotically revived memories often combine fact with fiction. Under hypnosis, people are more likely to use their imagination to construct or retrieve their recollections. Consequently, there is a danger that people will confidently assert having a memory of something they never experienced.

Hypnosis continues to be an active area of research. It is used in psychotherapy and is sometimes useful in alleviating chronic pain . Regardless of what the under- lying mechanism might be, there is no evidence that hypnosis produces exceptional psychological feats or behaviors.

Automatic and controlled processing

It's not easy for us to talk on the phone while simultaneously carrying on a conversation with somebody else in the same room. Such difficulty illustrates a fundamental principle of cognition, namely that our cognitive resources are limited. We simply do not have the mental wherewithal to focus on several different tasks at once. If so, how do we manage to execute two activities at the same time, for example reading the newspaper and listening to the radio? The answer is that there are two different levels of conscious control over our behavior. The first is referred to as "automatic processing" because it requires relatively little conscious awareness, and makes little demand on limited attentional capacity. When a person drives a car while mentally reviewing the previous days' events, he is demonstrating automatic processing. Automatic processing develops with practice as the component parts of the activity become well learned.

"Controlled processing" refers to behaviors that require effortful and deliberate concentration. It requires substantial use of cognitive resources. Consequently tasks requiring controlled processing can usually only be performed one at a time. Automatic processing is rapid and effortless, but somewhat inflexible. Controlled processing is slower, effortful, but adaptable.

This distinction between automatic and controlled processing is directly relevant to the current controversy about the use of cell phones while driving. There is good evidence to suggest that such behavior poses significant risks. For most adults, driving a car is a relatively automatic activity. For this reason, talking on the phone while driving may seem like a victimless crime. However, driving is not always automatic. When the unexpected happens, concentration is required. A driver in the midst of an animated conversation may not recognize an impending emergency and/or may not be able to respond with appropriate speed when it is recognized.

Subliminal perception

To what extent can we be influenced by stimuli whose presence we are not even aware of? There are numerous laboratory studies that show that individual words can be processed, even when presented so quickly that the viewer has no awareness of the word's identity. There is also evidence that patients under general anesthesia can apparently remember information (i.e., words) presented while they are unconscious. But what about more extraordinary claims? Can we be induced to buy a product or change our behavior on the basis of images or directives that are presented outside of conscious awareness? In a word, no. Before changing one's habitual response to a stimulus, one would have to be aware of perceiving it. There is no evidence to suggest that people initiate actions on the basis of subliminally presented stimuli.



Merikle, P. M., & Joordens, S. "Measuring unconscious influences." In Scientific Approaches to Consciousness. Ed. by J. D. Cohen & J. W. Schooler. Mahwah NJ: Erlbaum,1997.


Greenwald, A. W. "New look 3: Unconscious cognition reclaimed." American Psychologist 47 (1992): 766-779.

Moore, T. E. "Subliminal perception: facts and fallacies."

Skeptical Inquirer 16 (1992): 273-281.

Timothy E. Moore, PhD

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Consciousness, Levels of

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