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Hemispheric Specialization

Updated on October 7, 2014

Since the beginning of scientific interest in the human brain, philosophers, physiologists, and psychologists have been trying to determine specifically what parts of the brain are responsible for what behaviors. Advances in experimental procedures and technology have led scientists to draw many conclusions about the functional organization of the brain.

What conclusions have scientists been able to reach about the functional organization of the brain? We know that the hippocampus is important in forming new memories and the cerebellum is important in movement and balance.

Further, the thalamus acts as a relay station for the senses and the medulla specializes in basic bodily functions like breathing and maintaining a heartbeat.

Even the hemispheres of the cerebrum have undergone detailed studies to try to determine if there are specialized functions associated with the two sides of the brain. In trying to answer these questions, split-brain research has helped scientists immensely. The "split-brain" procedure is a surgical technique used for patients who have a seizure disorder and for whom anti-convulsant medications do not help to stop the seizures in the brain. The procedure involves separating the two hemispheres of the brain by severing the corpus callosum.


The corpus callosum is a cluster of several nerve fibers that connect the left and right hemispheres, allowing each hemisphere to send information to the other. Severing the corpus callosum can reduce the likelihood that a seizure will spread from one hemisphere to the other.

One clear finding in split-brain patients and in normal brains is that the two hemispheres control movements on the opposite side of the body.

The right hemisphere directs muscles on the left side of the body and the left hemisphere directs muscles on the right side of the body. The sense of touch is also represented on the "contralateral", or opposite, side of the brain.

Even emotions seem to be lateralized in the brain with positive emotions being associated with activity on the left side of the brain and negative emotions associated with activity on the right side of the brain.


Popular culture also likes to separate functions in the hemispheres by stating that the left hemisphere is the "analytical" side of the brain, and the right hemisphere is the "creative" side of the brain. However, scientific studies do not support such sweeping generalizations about hempisheric specialization. (Sperry, 1982).


In fact, the only functions that are clearly lateralized are language skills and spatial relations skills (Corina, et al., 1992; Peterson & Fiez, 1993; Bradshaw & Nettleton, 1981). Well-designed and controlled studies consistently find that the left hemisphere is superior in language function while the right hemisphere is superior in spatial relationships. You will test this assumption yourself in this experiment.

This experiment that you are about to participate in will test the language abilities of the two hemispheres of the brain. Because the visual fields become lateralized in the brain, information presented to the right visual field is projected to the left hemisphere of the brain, and information presented to the left visual field is projected to the right hemisphere of the brain.


Therefore, we can expose the two hemispheres to a language test and use it to determine if the left hemisphere is dominant in language function

To begin each trial in the experiment, you will be asked to press the "space bar" on your keyboard. Once you press the "space bar", you will see a red dot in the middle of the screen. (Again, as depicted in the mock image on the left.) Please stay focused on the dot as it flashes three times. After the third flash of the dot, a group of letters, or letter string, will be presented to the left or right side of the dot. The letters will be presented for a fraction of a second. When you detect the letter string, you are to determine if it represents a "real" word, of if it is a nonsense combination of letters. You need to determine whether or not it is a word as quickly as possible.

If the letter string represents a "real" word, please press the "R" key on your keyboard. If the letter string represents a nonsense combination of letters, press the "U" key on your keyboard. Please remain focused on the red circle in the middle of the monitor. Keep one thumb on the space bar and your index fingers on the "R" and "U" keys at all times.


You will be given 5 practice trials before the experimental trials begin. The computer will track the amount of time it takes you to respond and whether or not you are accurate in determining if the word is "real" or not.

The independent variables are the type of word, either real or nonsense, and the location of the letter string, either left or right. Take a moment now and hypothesize what might happen in this experiment.

The dependent variables are the length of time it takes you to respond, and the accuracy of your response. Now hypothesize what might happen in this experiment.

In preparation for the actual experiment, first complete this shortened, practice experiment consisting of 5 practice trials in order to acquaint yourself with how to interact with the experiment using your keyboard. Remember, you need to stay focused on the red dot in the center of the screen and respond with an "U" if the word flashed on the screen is a nonsense word, or respond with a "R" if the word is an actual word.

When the text string appears, do not shift your gaze to it. Instead, keep focused on the red dot and try to read the text with your peripheral vision. Keep your face as close to the computer screen as is comfortable to further ensure you are viewing the letter strings with your peripheral vision. About 12 to 18 inches away is optimum.

Practice Results

Your Responses:


Stimuli presented on right
-------------------------------------------------------------------
You correctly answered that the word 'JELBY' is not real.
You correctly answered that the word 'SLIDE' is real.

Stimuli presented on left
-------------------------------------------------------------------
You incorrectly answered that the word 'STARM' is real.
You correctly answered that the word 'GRAPE' is real.
You correctly answered that the word 'RIGHT' is real.

Now that you've completed the practice experiment with 5 trials, you can proceed to the actual experiment with 40 trials. Please be conscientious and respond to all trials as quickly and diligently as you can. This experiment will take between 10 and 12 minutes to complete. If you cannot complete the entire experiment in one sitting, the results will not be vali

My Results

Earlier, you hypothesized whether you believed the right or left hemisphere would be faster and more accurate at determining if the letter strings being flashed on the screen were "real" words or nonsense.

Because the left hemisphere is more specialized in language function, we would expect that your left hemisphere was more accurate and faster when determining whether letter strings were real words or not.

Click on View Global Results to see if your hypothesis about your right and left hemisphere was correct. Also find out how your results compare against the global population of people who have completed this online experiment.

Recall that the two independent variables in the experiment were the side the letter string is presented on (left presentation or right presentation) and whether the letter string represented a real or nonsense word. Your responses below are grouped by whether the letter strings followed a Left Presentation or Right Presentation and green indicates your response was correct, red indicates your response was incorrect.

Your Responses:


Stimuli presented on right
-------------------------------------------------------------------
You correctly answered that the word 'JELBY' is not real.
You correctly answered that the word 'SLIDE' is real.
You correctly answered that the word 'TROOL' is not real.
You correctly answered that the word 'TABLE' is real.
You correctly answered that the word 'WHERE' is real.
You correctly answered that the word 'DRIPE' is not real.
You correctly answered that the word 'FRAME' is real.
You correctly answered that the word 'MOOSE' is real.
You correctly answered that the word 'PAILS' is real.
You correctly answered that the word 'BURST' is real.
You correctly answered that the word 'BROWN' is real.
You incorrectly answered that the word 'GOSSE' is real.
You correctly answered that the word 'SENGS' is not real.
You correctly answered that the word 'COUCH' is real.
You correctly answered that the word 'BLACK' is real.
You correctly answered that the word 'TRIBL' is not real.
You correctly answered that the word 'CHARM' is real.
You correctly answered that the word 'BRAIB' is not real.
You correctly answered that the word 'CHAOR' is not real.
You correctly answered that the word 'BOATS' is real.

Stimuli presented on left
-------------------------------------------------------------------
You incorrectly answered that the word 'STARM' is real.
You correctly answered that the word 'GRAPE' is real.
You correctly answered that the word 'RIGHT' is real.
You correctly answered that the word 'GROUP' is real.
You correctly answered that the word 'DREAM' is real.
You correctly answered that the word 'RIVEX' is not real.
You correctly answered that the word 'CURLY' is real.
You correctly answered that the word 'HORSE' is real.
You correctly answered that the word 'LEERN' is not real.
You correctly answered that the word 'STRIP' is real.
You correctly answered that the word 'FALST' is not real.
You correctly answered that the word 'REACH' is real.
You correctly answered that the word 'ROSST' is not real.
You correctly answered that the word 'YARTS' is not real.
You correctly answered that the word 'APSLE' is not real.
You correctly answered that the word 'PHONE' is real.
You correctly answered that the word 'RADIF' is not real.
You correctly answered that the word 'PEACH' is real.
You correctly answered that the word 'SMILE' is real.
You correctly answered that the word 'STAKT' is not real.
You correctly answered that the word 'PLEAG' is not real.
You correctly answered that the word 'TRIRK' is not real.
You correctly answered that the word 'PROAF' is not real.
You correctly answered that the word 'STOLE' is real.
You correctly answered that the word 'SHEFG' is not real.

Reaction Time

Percent Correct

How do your experiment results relate to what you have learned in this module? What insights did you gain about cognitive processes and associated research methods by participating in this experiment?

I was surprised at how slow my reaction time was and how high my percent of correctness was. For reaction time I had an average of 580.9 for my right brain hemisphere and a 504.2 for my left brain hemisphere. Both of these were much slower than the global average of reaction time which surprised me because I thought I was pretty quick when I was taking the test. I was however pleasantly surprised to see that on the left side of the presentation I answered all of the questions with 100% accuracy and the right side of the presentation I answered with 94.4% accuracy. My accuracy levels were both above the global average by 8.6% and 5.9%. I believe I scored the way I did on the test because I was focused more on getting the answers right then getting them answered the fastest. If I had focused more on the time I was spending on answering I believe my response time would have decreased and my accuracy would have fallen.

In relation to this week’s module I researched what the right and left hemisphere of the brain specialize in. I found that the left hemisphere is “the logical brain responsible for words, logic, numbers, analysis, lists, linearity and sequence” (The Thinking Business, 2014). I also found out that the “right brain is the creative brain and is responsible for rhythm, spatial awareness, color, imagination, daydreaming, holistic awareness and dimension” (The Thinking Business, 2014). Knowing this I believe that the Hemispheric Specialization Experiment could be changed in order to create a test to discover if the person taking the test leans more towards logic or creative thinking based on which part of the brain he or she uses the most and with the highest accuracy. The results of this test could prove helpful to teachers because if they knew more about how each of their students think then they would be able to better gear lesson towards their students.

References

Ashcraft, M.H., & Radvansky, G.A. (2014) Cognition (6th ed.) Boston. Prentice Hall.

MyPyschLab. Experiment: Hemispheric Specialization. http://pet.pearsoncmg.com/dashboard

Brain Hemispheres. (n.d.). The Thinking Business. Retrieved September 28, 2014, from

http://www.thethinkingbusiness.com/brain_zone/brain-tour/brain-hemispheres

How many F's in the sentence below?

"When in the course of influencing efficacious functions of human faculties often farfetched fairytales are fructifying and fortifying of fateful foibles."

There are 7 "f" letters on line one and 12 on line two for a total of 19.

Try reading backwards or upside down to counteract the language effects on words like “of” that sound like a “v” and the brain screens out.

Clearer Understanding: Better Decisions

To make our best decisions, we need to gather and process the best input possible. Often the input may not be from the outside world, but from ideas that are already in our heads. Then the decision-making is often ruled by dictatorial ideas that appear entitled just because of being in our heads. It might be called an “Ideaocracy”.

Generally, a meritocracy is desirable for choices. With ideas, that means checking the merits by testing facts (evidence) with our senses, consulting experts, and using rational (proportional) judgment.

An analogy for obtaining and processing the valuable input is a zoom lens and video screen. For great decisions, the zooming in is about:

  1. Source: Who says so?
  2. Specifics: What are details?
  3. Substance: Where is the proof?

And the zooming out is about:

  1. Perspective: What is big picture?*
  2. Priority: What is important?
  3. People: Who else cares?

* Will the decision matter in a year? Five years?

To “Use a comprehensive system to clarify quick decisions and efficiently deal with major decisions about jobs, relations, homes, etc.”

Reference: Goldstein, E. B. (2011). Cognitive psychology (3rd ed.). Belmont, CA: Wadsworth.

To know yet to think that one does not know is best;

Not to know yet to think that one knows will lead to difficulty.

It is by being alive to difficulty that one can avoid it.

The sage meets with no difficulty.

It is because he is alive to it that he meets with no difficulty.

— Tao Te Ching”, Chapter 71

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