Consciousness - An Introduction (ch20)

How can we distinguish between reality and imagination? - Chapter 20

Distinguishing

In daily life we ​​often distinguish between the outside world and what goes on in our heads. We do this without knowing that we use a skill for this. This skill is called ' reality monitoring' or ' reality discrimination' . Research shows that 'reality monitoring' is influenced by our expectations about whether something is real or imagined. For example, Perky asked people to look at a blank sheet and to imagine that a tomato is depicted there. Without the people being aware of it, it was ensured that a picture of a tomato was projected onto the back of the leaf. Despite the fact that it became increasingly clear, participants continued to believe that it was their own imagination.

Distinguishing between events that have really happened and things that we think happened tends to be difficult. 'Memories' of events that never happened, are also called ' false memories' .Real memories can be determined because we can place them in a context. This is also called ' source monitoring' . ' False memories' can be easily generated in the laboratory. They can continue to work for a long time.

Hallucinations

It is important to make a distinction between hallucinations and illusions. Hallucinations are experienced entirely from within, while illusions are misinterpretations of external states. Examples of visual illusions are the Muller-Lyer illusion and the Ponzo illusion . Hallucinations are perceptual experiences, while there is no external stimulus.

True hallucinations are sometimes distinguished from pseudo-hallucinations . With pseudo-hallucinations, the person himself knows that the hallucinations are not real. For example, if you hear a voice in your head, but know that this can never be real, then there is a pseudo-hallucination. In addition, a distinction is made between hallucinations and mental imagination. Hallucinations are uncontrollable and therefore can not ' go out' of your head if you do not want to think about it anymore. The distinction between hallucinations and mental imagination is not very clear.

What happens in the brains of people who are hallucinating? Many studies show that there is activity in hallucinations in the brain regions that would also be active if people actually heard an angelic choir (or whatever hallucination they have). However, there is also evidence that complex interconnections are involved. How real the hallucinations seem to be depends on how many areas of the brain are involved.

Definition

Slade and Bentall state that a hallucination is an experience that:

1. occurs in the absence of a stimulus,              

2. has a great influence on real perception, and             

3. can not be voluntarily controlled.

Hallucinations are common in people with schizophrenia. The symptoms of this disorder vary per person. For example, schizophrenic people may feel that alien creatures determine their behaviors. Often they hear voices from, for example, fairies that are in the walls. These hallucinations are experienced as real.

Although hallucinations are often aligned with pathology, there are several reasons to reject this. Firstly, it is not clear how hallucinations can be distinguished from other experiences and secondly, hallucinations are common in the population. Third, there are cultural differences in attitudes to hallucinations. In some cultures, people look very positive about hallucinations.

Research shows that visual hallucinations occur more often than auditory. Women also report having hallucinations more often. The most experienced hallucination is that people see someone who does not really exist.

Context and content of hallucinations

Some hallucinations occur spontaneously and others are caused by drugs, illness, hunger, lack of sleep or the use of rituals. No sensory input increases the chance of hallucinations. The sensory systems then try to use everything we have received and use a different criterion for what is a real experience. Jackson came with the ' perceptual release theory' to explain hallucinations.

According to this theory, memories are normally inhibited by sensory information. This is not the case with hallucinations. There are many different hallucinations, but they do have common characteristics. People often see spirals, certain patterns, wavelengths and bright colors. How can it be explained that these characteristics often correspond to people?

Kluver investigated this using the anesthetic mescaline. He discovered that the use of this product results in people perceiving bright colors in different forms. These forms are tunnels, spirals, webs and grids. These forms are all found in hallucinations caused by other drugs, but also in hallucinations due to fever, migraine and epilepsy.

Where do these agreements come from? The cause of these similarities could be related to how the visual system in the brain is organized. The primary visual cortex is organized in column form. Spirals, tunnels, webs and grids go together with lines in different directions. This means that when activity spreads in straight lines within the visual cortex, the experience is equivalent to looking at real rings or circles. A reason why lines are activated in the visual cortex is disinhibition . Drugs, lack of oxygen and certain diseases can affect inhibitory cells; much more than on activating cells. This creates an extremely high amount of activity that can spread in the brain in a linear way. This ensures the experience of tunnels, spirals, webs or grids.

There are also similarities in the movement and colors of hallucinations. In more complex hallucinations, there are also similarities between people's experiences. For example, people often see cartoon-like creatures, great cities, animals and creatures from myths. Siegel and Jarvik discovered that when using drugs, people first have simple hallucinations, then experience tunnels and schedules and then experience complex hallucinations.

To sleep

We often have hallucinations just when we almost fall asleep. Maury called these hallucinations ' hypnagogic images' or ' hypnagogic hallucinations'. Hallucinations that arose upon awakening, he called ' hypnopompic images'. People at these moments feel that they are flying or are falling through tunnels. It sometimes happens that people who have been engaged in a task all day, see images of this task just before they go to sleep. Others think at that moment that someone is calling their name. Then there is also something like sleep paralysis . During REM sleep everyone is paralyzed. For this reason, no one can perform what he or she is dreaming about at that moment.

Consciousness during sleep paralysis occurs when normal paralysis during REM sleep begins too late, the person just falls asleep or when paralysis takes too long when someone is awakening.

Other worlds

Children often have imaginary friends. Some children play and talk for years with the same imaginary friend. It also happens that imaginary friends are animals or invisible toys. Some people are said to have a ' fantasy-prone personality' . These people often have more imaginary friends than other people, because they can fantasize and be creative.

In many cultures, hallucinations are valued because it could be closer to ghosts or gods. An example is the Yanamamo strain that can be found in Brazil and Venezuela. They believe that there are spirits ('hekura') in the heavens and that they can penetrate the body of people from the chest. To invoke these spirits this strain uses ' ebene' : a green powder that causes hallucinations.

Resources: Blackmore; Susan. (2010). Consciousness, Second Edition An Introduction. Abingdon, Oxon: Taylor & Francis.