The purpose of this paper is to evaluate the correlational method as a means for examining the relationship between functions of the left and right hemispheres. I will compare the performance of people with intact brains with the performance of so-called split-brain patients. In many ways, the brains of these two groups are very similar. 1a. The location of the normal and split brain brainstem is in the head, connecting the cerebrum to the spinal cord. Its function is to regulate movement control messages from the brain to the body, such as heart rate. 1b. As for the hippocampus, it is found in the limbic system which lies at the border of the brainstem and the cerebral cortex. Its function involves storing memories and the normal brain and split brain do not have any differences regarding the anatomy of this part of the brain. 1c. The corpus callosum is found above the brainstem and under the cerebral cortex. Its job is to connect the left and right hemispheres of the brain but it is split in people who suffer from epilepsy, which causes the disconnection of the two hemispheres, ultimately changing the anatomy. 1d. Finally, the cerebral cortex is the outermost layer of the brain, made up of wrinkly and gray matter. It has many functions as it has four lobes that are responsible for different purposes such as memory, movement, sensory information, and decision making. The function of the cerebral cortex between normal and split brains are different as the cerebral cortex is linked by the corpus callosum, which is removed in patients with split brain. Therefore, the link between the two hemispheres is severed.
The split brain patient provides scientists with a window into the normal functions of the brain. 2a. Split brain patients suffer from severe epileptic seizures and must have a surgical technique, a corpus callosotomy, to alleviate the problem. By severing the corpus callosum, the left and right hemispheres of the brain become disconnected. 2b. A test that can explain how the language function is lateralized to one hemisphere is by making the patient hold an object with their left hand. Since information from the left hand is processed by the right hemisphere, the patient cannot name what the object in the left hand. However, when the object was put in the right hand, it was easily named because the left hemisphere in the brain is responsible for language and so it is lateralized to that hemisphere. 2c. The results explain laterality because it goes to show how specific functions of the body of split brain patients are lateralized to different hemispheres of the brain, the left or right one. The consciousness of an individual is split in half, where one side cannot perceive what the other is doing and thus, functions are lateralized.
Cognitive tests performed on split-brain patients have identified a division of labor between hemispheres. It is conceivable that functions handled by the different hemispheres will show a strong relationship in the general population, but not in split-brain patients. 3a. Functions lateralized to the left hemisphere are language, reasoning, movement of the right hand, and math. Functions lateralized to the right hemisphere are facial recognition, creativity, music, and movement of the left hand. 3b. The hypothesis to be tested is that individuals with normal brains have a positive correlation between the functions of the left hemisphere and the functions of the right while split brain individuals have difficulty managing connection. 3c. The correlational method will evaluate the hypothesis as it would show the relationship between the functions of the two hemispheres and then determine whether or not the hypothesis is correct. If it is a direct relationship, then there is a positive correlation. If there is an inverse relationship, then it would be a negative correlation.
Data were collected from a group of split-brain patients and a group from the general population to test the hypothesis using the correlational method. Each group completed three tasks shown previously to be lateralized: (1) a vocabulary test, (2) a logical reasoning task, and (3) a face recognition task. 4a. The vocabulary and logical reasoning are lateralized to the left while the facial recognition is to the right. 4b. I believe that the correlation for those with normal brains taking the vocabulary test, logical reasoning test, and facial recognition test would all have a positive correlation as the brain is intact and so connections between both hemispheres are stable. For split brain participants, the only positive correlation would be between the vocabulary test and the logical reasoning as both are lateralized to the left hemisphere. The other relationships would have a no correlation at all. 4c. For the data of the intact brain participants, it is as follows: vocabulary test and the logical reasoning was I = 78176, II = 59.78, III = 1542, and r = 0.71. Logical reasoning and facial recognition was I = 59.78, II = 116785.85, III = 2299.84, and r = 0.87. Vocabulary test and facial recognition was I = 78176, II = 116788.85, III = 60669.6, and r = 0.64. For the data of the split brain participants, it is as follows: vocabulary test and logical reasoning was I = 88909, II = 95.9, III = 2089.7, and r = 0.72. Vocabulary test and facial recognition was I = 88909, II = 108737.6, III = 33889.2, and r = 0.34. Logical reasoning and facial recognition was I = 95.9, II = 108737.6, III = 137.2, and r = 0.04. All data is rounded to the nearest hundredth.
The results of the correlational method were valuable in addressing the hypothesis under study. However, future investigations may need to adopt techniques that improve upon those used here. 5a. The hypothesis was that the correlation for those with normal brains for all tests would be positive and that for split brains, it would all be negative except for the vocabulary test and logical reasoning. The correlational study was found to be consistent with the hypothesis because in the left hemisphere, language is dominant along with logical reasoning. However, in the right hemisphere, facial recognition is dominant. Therefore, the relationships between the studies for participants with intact brains would be strong because their corpus callosum is not severed, meaning that both hemispheres can connect with one another and thus, there would be a positive relationship. However, for the split brain participants, only their vocabulary test and logical reasoning had a positive correlation because both are lateralized to the left hemisphere. The facial recognition, which is lateralized to the right, cannot readily connect with the other two because the corpus callosum is severed and thus, there is a disconnection between the studies. Essentially, the vocabulary and facial recognition and the logical reasoning and facial recognition relationships have a negative correlation as a result. 5b. One aspect that does not fit is that it was predicted that the relationships besides that of the vocabulary and logical reasoning tests would have no correlation because I assumed that, since there is a disconnection, there would be no relationship. However, there was, but it was a negative one because there could be a disconnection but it would be too weak. 5c. The current correlational technique can be improved by reducing the number of relationships that must be evaluated to two instead of three. For example, we can remove the logical reasoning test and only evaluate the participants on their vocabulary test and facial recognition test to obtain fewer answers which would lead to clearer results. 5d. Correlational studies can be used to evaluate hypothesis because the point of them is to make predictions of the influence one study has on the other. However, that does not mean that we can use them to evaluate the causes on the relationship between the studies because correlation is not equivalent to causation. Therefore, we can use correlational studies to interpret our hypothesis but only for that specific purpose. 5e. An experiment one could use to test the hypothesis is to display a word or a picture on a screen or make participants hold physical objects with both hands. Then, they would be asked a variety of questions such as being asked to draw the objects, point to it, verbalize it, correspond it to other objects, or be asked questions that evaluate their logical reasoning behind it. The results of the answers of both intact and split brain participants would be compiled into data in which we could analyze the lateralization and difference between the minds of those with normal brains and those with a split one.