What is the interpretive nature of the left brain?

In this article, we’ll look at Michael S. Gazzaniga’s “split-brain research,” which continues and develops the work of Roger W. Sperry, to get to the root of the “narrative human”.

 

We are cause-and-effect animals. “Why?” has been a central question in human history. “Why do thunderstorms and storms make us suffer?”, “Why doesn’t it rain?”, “Why do people die?” These questions, of course, were sparked by humans’ fears as they tried to survive in the not-so-gentle world of nature in early civilizations. At first, they created religion. God, or gods, were the source of nature beyond human understanding and the center of destruction. Humans believed that the wrath and anger of the gods was responsible for natural disasters like droughts and floods. They sought out sacrifices to offer them, built altars, and prayed to them. Myths and scriptures were written and they were the way humans interpreted and accepted the world. This is also found in the realm of academia. In ancient Greece, they tried to make natural phenomena more logical. They debated what nature consisted of and what its most basic elements were. These discussions would go further, analyzing the societies they lived in and extending to discourses about states and war. In China, thinkers also criticized and proposed solutions to the violent conditions of the time. In the process, it was essential to “understand” and “interpret” society.
Myths and religions were found all over the world, with only minor differences. Analyses and interpretations that exclude gods, and understandings of society and the state, are also found in different cultures around the world. From this universal phenomenon of humans analyzing phenomena in one way or another and trying to find cause and effect, we can understand that it’s in our nature. And to the question of where this nature lies, I would say that it is directly related to our human brain, because the operations that deal with our language and thinking take place in the brain, and therefore the way the brain understands the world as a phenomenon and the way humans understand the world within structures such as society are similar or identical. To do this, we need to look at studies that analyze how the brain takes in the world.
As most people already know, our brain is divided into compartments. The largest part of it is the cerebrum. It’s made up of two hemispheres, the left and the right. Between these two hemispheres is an area called the corpus callosum, which is formed by the union of countless nerve cells. This area, called the corpus callosum, connects the two hemispheres of the cerebrum, as can be inferred from the fact that it contains many nerve cells. Signals that normally access the brain via the spinal cord go through the pons and the thalamus in the midbrain, so they reach both hemispheres relatively equally, even if they don’t pass through the corpus callosum. This means that parts of both hemispheres of the brain are connected to the midbrain and can exchange information with each other. However, when the corpus callosum is severed, information that travels across the corpus callosum, such as visual information, is not able to do so. Visual stimuli are a prime example of such information. When the corpus callosum is removed, the left brain cannot see objects in the left visual field and the right brain cannot see objects in the right visual field. In terms of information exchange, the corpus callosum is a very important area.
However, some people have had surgery to cut it off. This surgical technique, called a corpus callosotomy, has been shown to reduce the symptoms of epilepsy. This makes sense when you consider the function of the corpus callosum, since epilepsy is a disease caused by abnormal signaling in localized areas of the brain, or throughout the brain as a whole. Patients who suffer from seizures at any time of the day or night would undergo this surgery, which was possible because the function of the corpus callosum was not clearly understood at the time. Patients who underwent this surgery were surprisingly able to lead normal lives afterward without much difficulty. It was Dr. Roger Sperry who began to study these people, and his research clearly demonstrated lateralization, which refers to the tendency of both hemispheres of the cerebrum to specialize in different roles. Lateralization, which had previously been indirectly confirmed through speech impairment caused by damage to the left hemisphere, was confirmed. However, Dr. Michael Gazzaniga approached the issue in a different way and found a “left brain that interprets” alongside the ubiquity of ubiquity.
In “Cognitive Neuroscience: The Biology of The Mind,” Dr. Gazzaniga describes a split-brain patient (P.S.) who was given a piece of paper with specific instructions and presented it to his left visual field, or right brain. If the instruction was something like, “Get out of your seat,” P.S. would naturally get out of his seat. The problem came next: when the patient was asked to explain why he got up, he said something like, “I was just going to get a coke.” Even though he was acting in accordance with the instruction, he didn’t do it at all. This completely wrong answer, even though the behavior was in accordance with the instructions, could be interpreted as a sign that the subject was “unaware” of the instructions and was trying to justify his behavior.
This is why Dr. Gazzaniga used the simultaneous concept task in his Separate Brain Study (1978) with Dr. Joseph E. Ledoux. According to Cognitive Neuroscience, split-brain patients are presented with two different pictures in both hemispheres, i.e., different starting information is presented to different visual fields. In this process, the left eye can’t recognize the information presented to the right eye, and the right brain can’t recognize the information in the left visual field. Once this is confirmed, the subject chooses two pictures from a row of pictures that are similar or related to the two pictures they saw. For example, in the above P.S., a picture of a snowy street is presented in the left visual field and a picture of a chicken’s feet is presented in the right visual field. From the set of pictures presented in a row, the correct association would be to find and select the shovel used to clear the snow and the chicken. In fact, the patient selected the shovel with his left hand and the picture of the chicken with his right hand, and the experimenter asked the split-brain patient why he chose those two pictures. For the picture of the chicken, the subject said that he chose the chicken because he was presented with chicken feet. In other words, P.S. was trying to explain his behavior as logically as he could with what he already knew about his behavior, using what he already knew about his behavior, revealing that he was unable to comment on the visual information being sent to his right hemisphere for whatever reason – that he was unaware of the snowy scene. Dr. Gazzaniga’s interpretation is that the corpus callosum resection prevented the left and right hemispheres from exchanging visual information, which is why the right brain’s choices and the left brain’s choices didn’t make sense to each other. However, the part of the brain that is mainly responsible for language is ubiquitous in the left hemisphere, so only information perceived by the left hemisphere could be expressed in language. That’s why P.S. was able to tell the truth about why he chose the chicken, but not the shovel, as described above. From these experiments, Dr. Michael Gazzaniga concludes that the left hemisphere is solely responsible for a large part of language and tends to interpret phenomena and situations.
The split-brain experiments have shown that the left and right hemispheres of the cerebrum play a role in each other, and that the left brain is responsible for language and logical, causal thinking. While the right brain is certainly capable of perceiving objects and processing information, it is the left brain that actually triggers the type of information we communicate to others, especially information that consists of speech or visual symbols. The other thing we should pay attention to is the left brain’s “excuses”. Michael Gazzaniga writes in Cognitive Neuroscience that his patients were clearly trying to make excuses for their choices and explain their reasons as logically as possible. In other words, the left side of the brain, which is responsible for language functions, approaches phenomena with a more interpretive and analytical perspective. Michael Gazzaniga adds that this suggests that our tendency to think rationally comes from the left side of the brain, which means that our cognitive structure is such that we constantly make up words to make sense of things.
When there is a gap between what we understand and what is happening in reality, we use our own way of making up stories and structuring them. This characteristic of the left brain, as revealed by neurodiversity research, gave rise to ancient myths and age-old tales, upon which we built our understanding of the world. We adapted and modified those stories to understand nature and society in a more sophisticated way, which was expressed in ancient philosophies. Humans are not so different now. The story-based structure remains the same in our modern, science-driven, rational worldview. A series of stories in which atoms and subatomic particles are the protagonists and in which we read the rise and fall of the “great kingdom” of living things and chemical reactions are the myths and stories of our time. In them, the laws of physics are given the status of gods, and everything made of particles is a giant narrative structure and heroes. We try to feel the world through such grand narratives, even as their structure gives us vision and takes it away.