hypnosis Stroop Effect

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Cognitive Neuroscience: How the Brain Works

Section Summary

Some might find the topic of neuroscience a bit daunting. Don't panic. Relax, take a deep breath. There will not be any test questions on this information. Read the summary below, continue take the quizzes, complete the course and purchase our document package. Here is a concise summary of the important points covered in this section:

  • The Stroop Effect shows how one area of the brain can dominate and inhibit other functional areas.
  • The anterior cingulate cortex has been shown to active during hypnosis and also during Stroop tasks.
  • "Local" processes like speaking or reading are associated with weakening suggestibility.
  • "Global" processes group things together like patterns, colors, phrases, clichés, or metaphors and tend to deepen suggestibility.
  • Hypnosis can eliminate the Stroop Effect, while training cannot.

Cognitive Neuroscience

Different areas of the brain specialize in specific tasks, and when one area of the brain is active it can suppress activity in other areas. The right brain vs. left brain paradigm so often rolled out in pop psychology is in fact not so clear cut. Although at first glance the human brain appears symmetrical (with the left side and right side being mirror images of each other)  It has long been known this not entirely true since simple dissection will reveal for example that the areas for speech are developed on the left side of the brain and the corresponding section on the right is undeveloped (this is true for about 96% of the population).

The two sides of the brain are connected by a massive bundle of nerve fibers called the corpus callousum. As a treatment for severe epilepsy this connection is sometimes surgically severed. Remarkable the patients of this type of operation generally appear to function normally. But under closer testing it has been shown that in fact there is lateral specialization of the brain. Patients handed unseen objects could describe them when placed in their right hand, but not objects place in the left hand.  The left side of the brain controls the right side of the body and vice versa.

All right-handed people have left hemisphere specialization for language. In addition 50% of left-handed people have their language function dominate on the left side. Since left-handers make up 7-8% of the population it turns out 96% of people have language processing on the left hemisphere of the brain. When their brain is surgically split into two independent units the right side was not able to verbally articulate a description of the object held in hand.

Later we will see how language center activity affects hypnotic state.

It has also been observed that tumors on the left brain can adversely effect verbal ability. Tumors on the right side of the brain do not effect verbal abilities for 96% of the population that suffer them. 

Many of the fibers of the corpus callousum connect the physically mirrored sections of the brain. For example the frontal lobe on the left side might be directly connected to the frontal lobe on the right side. One theory of the function of these connections is that they are inhibitory, meaning that if the right frontal lobe is active signals travel through the corpus callousum and suppressing activity in the left frontal lobe. Similar to the patients with their corpus callousum cut, intact brains produce behavior with one side dominating the other and inhibiting its activity.

A 1998 study conduct by Henry Szechtman of McMaster University in Ontario using PET scanning of hypnotized people showed brain activity in the right anterior cingulate cortex when the subjects were instructed to hallucinated a sound. This activity was not seen in the control group of non-hypnotized subjects who were instructed to imagine hearing a sound.

global and local stimuliWhile the brain is remarkably adaptive, and many areas can function outside their areas of specialization, the left-brain dominates in language, speech, and major problem solving, and right in spatial tasks like drawing or sorting patterns. Both side can generate facial expressions spontaneously but only the left can voluntarily create an expression.

 Computer Analogy

We have all heard the assertion that people use only 10% of their brain. This is a myth. You might only use 10% at any one time, but it is all used for something. Claims that you can increase your productivity, creativity, or intelligence by using the “dormant” parts of your brain are just what they sound like – too good to be true. Apparently there are structural reasons and functional area specializations that make it impossible and actually inefficient to use all of your brain at one time.

An analogy of this from computer science would be to compare the human brain to a memory in a computer. Your PC has several different types of memory:

The L2 cache – small and the fastest type in part because it is so small. The L2 is directly accessible by the processor and as fast, or nearly as fast as the processor.
RAM – random access memory, fast but not as fast as the computer processor.
Hard drive – not fast but has a lot of space
Video RAM – Has direct access to the video display, but is more difficult for the processor to access.

To optimize a task on the computer all of the memory is used. The type of memory used depends on the type of task. Mathematical processes use the L2 cache. Very large files must be stored on the hard drive. The Ram is used to page through sections of large files and store instructions that are too large for the video RAM or L2 cache. The video RAM stores individual images that are paged through on the display screen.

Processes on the computer are optimized because it does not use all the memory resources in every task. A mathematical problem will be solved less quickly not faster if must be written to the hard drive. Images would display slower if they were to be process through the small size of the L2 cache instead of the larger video RAM with its big band width connection to the display. While the slowest the hard drive holds many times the amount of information as the others combined. When certain tasks need to be completed only certain areas of RAM are utilized.

Similarly in the human brain language is processed in one specialized area. This area has been optimized through evolution for this purpose. Victims of stroke and brain tumors have demonstrated that other areas of the brain can eventual perform these language functions, but they are not as efficient at it as verbal center on the left side of the brain. In a normal healthy brain the optimum efficiency comes from letting specialized areas perform common, yet intense tasks, such as speaking or recognizing the hue of a color. When we perform certain specific tasks the other areas of the brain that are slower at that specific task then the optimized area, are shut down and inhibited from controlling our behavior. 

The Stroop Effect

The Stroop effect shows how the brain deals with conflicting information. It is interference in the completion of a task caused by one area of the brain dominating and inhibiting the response of other functional areas.

Two sets of words, the second set demonstrates the Stroop effect. Say the color of these words are printed in as fast as you can:

Green Red Blue White
Yellow Blue Yellow Black

Blue Yellow Red White
Green Yellow Green Black

Due to the Stroop effect, the first setresults in a faster reaction time with fewer errors. 

The classic example is a color identification task where words naming a color such as blue, green, red, etc. are presented in a color different from the color expressed by the word's meaning (e.g. the word "red" printed in blue ink). A delay occurs in the processing of the word's color, leading to slower test reaction times and an increase in mistakes. The effect is named after its discoverer, John Ridley Stroop, and was first noted in the Journal of Experimental Psychology in 1935. In his experiment, Stroop asked participants to verbally identify the color of each word is printed in.

Additionally Stroop tested his participants at different stages of practice with each task, to account for the effects of association. Stroop identified a large increase on the time taken by participants to complete the NCW (Naming Colored Words) tasks, an effect still pronounced despite continued practice at each task.

This interference is caused by the dominance of functional area of the brain that interprets written language, where the brain determines the meaning of words. Interpreting written language and speaking are classified by scientists as a "local stimuli."

brain areas

This functional area is on the left side of the brain.  Stroop tasks are also employed to study area function in brain imaging studies using fMRI and EEG. These studies have shown selective activation of the anterior cingulate cortex during a Stroop task. 

Stroop effects cannot be reduced by training. The brain cannot be trained using normal methods to allow certain areas to dominate conscious control of our behavior. However Dr. Amir Raz, an assistant professor of clinical neuroscience at Columbia has shown that through hypnotic suggestion the Stroop effect can be eliminated.

It is well known that verbal activity can reduce the depth of hypnotic trance. The functional area of the brain that is usually dominant is also responsible for language function and critical rejection of suggestion.

The easily suggestible areas of the brain are also responsible for global activities like interpretation of visual stimuli like color, and global, “big picture” stimuli like metaphors, clichés, and phrases.  Other areas of the brain that are easily suggestible control our behavior when under strong emotions like fear or anxiety.

Summary of Global and Local processes
Understanding metaphors Interpreting written language
Understanding cliches Verbal activity (speaking)
Pattern recognition  
Using a common phrase  
Visually processing colors  

The brain has limited attention resources; only one functional area can control our behavior at a time and this inhibits the other areas. As we have seen different areas of the brain interpret and process stimuli in very different ways.  The task as a hypnotist is to help the subject stimulate a suggestible functional area, while inhibiting the critical functional areas. Since multiple brain areas could be utilized to accomplish this there numerous methods to induce hypnotic trance.

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