Consciousness, Sleep, and Altered States

Defining Consciousness

Consciousness is an individual's subjective awareness of their internal mental states and environment. Most cognitive, emotional, and perceptual processing takes place outside of conscious awareness.
Consciousness is defined as the subjective awareness of one's internal mental states and environment. Austrian neurologist Sigmund Freud first distinguished between conscious and unconscious aspects of behavior. The dominant modern theory of consciousness, referred to as dual-processing theory, divides consciousness into an implicit system and explicit system. The implicit system responds automatically to stimuli without conscious thought. For example, most people immediately recognize an angry face and tone of voice. They do not have to stop to think about what emotion is being expressed by someone who is yelling and swearing. The explicit process involves conscious awareness and deliberate cognitive effort. Solving a math problem requires explicit processing. So does thinking about what to say in response to a yelling and swearing person. Implicit and explicit processing can occur simultaneously and take place independently of one another. In serial processing, some or all processes involved in a cognitive task occur one after the other. In parallel processing, some or all processes involved in a cognitive task occur simultaneously. These simultaneous processes can and often do influence each other.
Consciousness is divided into an implicit system that operates outside of awareness and an explicit system that operates within awareness. Implicit processes take place simultaneously in parallel. Explicit processes take place one after the other in serial fashion.
Implicit processing is typically parallel. A simple example is driving and carrying on a conversation with a passenger. Drivers often simultaneously process conversations and visual stimuli seen through the windshield while operating the steering wheel, accelerator, and turn signal. People are capable of parallel processing because the brain consists of multiple information processing pathways working together.

Parallel Processing of Social Stimuli

Multiple regions of the brain process separate aspects of a situation at the same time (parallel processing). Even having a simple conversation requires people to handle multiple activities simultaneously, such as recognizing individuals, understanding their motivations, and making sense of their mental state.
A simple yet powerful demonstration of the implicit and explicit systems is the Stroop effect, named after American psychologist John Ridley Stroop (although German researchers identified this effect earlier). In this task, people are shown a list of color names in different-colored fonts. Their job is to identify the color of each word in the list. If the word name and font match one another (the word red is shown in red font, blue is shown in blue font, etc.), people have little difficulty quickly naming the color of each word. But if the name and font do not match (red is shown in blue font, blue is shown in red font, etc.), naming the colors becomes more difficult. This yields slower performance and more frequent errors. The difficulty arises because reading and color perception are both well-learned, automatic processes. The automatic output of the reading process must be controlled and overridden by deliberate decision-making to name the colors correctly. Children who know their colors but are just learning to read do not show the Stroop effect. As their reading proficiency improves, they begin to demonstrate the same pattern as adults.

The Stroop Effect

In the Stroop effect, competition between implicit and explicit processes (color naming and reading) makes it more difficult to read color names when the font color and color name are do not match one another.