When we start discussing about ideas still so dividing and controversial, we usually begin by wandering through philosophical realms before science is capable of providing us with stronger arguments. In neurosciences it is well understood that the brain is capable of creating illusions through a mechanism of ‘auto-filling’, which is useful during the process of making sense of the world around us with the information available at each moment. For example, let’s say you’re walking in the woods, at a given moment your brain perceives a snake dissimulated under the fallen leaves of a tree, adrenaline kicks in to make you aware of the danger and prepare yourself to ‘fight’ for your life. When you take a closer look, now with more information available because you focused all your conscious attention on that potential source of danger, you realize it is just an old rope and that there is no danger after all. At that first moment of reaction, your unconscious brain perceived a snake after sufficient information was available to increase the likelihood of it being a snake, and a primordial yet efficient defense mechanism was triggered, the “fight-or-flight” response. A series of inputs, like perceiving the woods as a propitious place for snakes, the sound of leaves being moved and an hidden object, somewhere in your field of vision, with a snake-like shape, triggered that response. The brain ‘filled in the gaps’ where information was missing, considering past experiences and genetic per-disposition, creating the illusion of a snake that wasn’t there after all. These illusions are created all the time in order to help us make sense of the world and be fit to ‘survive’ in it (I know we are not living in caves anymore but we bring a lot of baggage from those difficult times, evolutionarily speaking).
However, the idea that the sensation of having a self is an illusion itself, created by the brain, has been difficult to address out of the philosophical discourse. The illusion of the self is a theory that aims to describe the sensation of “I”, a sense of individuality, separateness and self-centered perception of reality, as a creation of the mind and the only thing there is that is aware of that sensation is consciousness. While this idea has been explored for millennia within religious and spiritual circles, being Buddhism the most impactful one, Science only had the audacity (and the resources, of course) to take on the challenge during the middle of the 20th century. A unique opportunity for research on the subject presented itself when a series of patients that were submitted to a callosotomy (a medical procedure to cut the corpus callosum, the main neuronal tissue that connects both brain hemispheres at the neocortex level) in order to treat serious cases of epilepsy started to show some strange yet interesting behaviors. These people are known as the “split brain patients”, and their condition is where I want to focus during the rest of this post.
Splitting the Brain
One of those patients is known in scientific literature as Vicky. Sometime after the procedure, Vicky started to experience some troubling behaviors. For instance, she would find a visit to the supermarket a complete ordeal. Both her hands would not agree on what to pick up from the shelf – “I’d reach with my right hand for the thing I wanted but the left one would come in and they’d kinda fight”. Getting dressed was also a challenge for the same exact reason. Her brain was behaving in some ways as if it was two separate minds. Before fMRIs became mainstream, these patients have proved valuable to determine differences between the hemispheres, which the communication highway has been severed. For example, the left side is where speech and language are mainly processed and the right side specialized in visual-spatial processing and facial recognition. Another patient, WJ, was asked, during one of the experiments, to press a button whenever he saw an image. The researchers would flash words to his left or right field of view . Since the light inputs in the left eye are processed by the right hemisphere and vice-versa, images presented to one side delivers the information to the respective hemisphere while the other is ‘blind’ to the stimuli.
WJ had no problem to tell the scientists what he saw when the stimuli was presented to the left hemisphere, or right eye. Yet, he would claim he didn’t see anything when the the image was shown to the right hemisphere, notwithstanding his left hand pressing the button every time a word appeared to the right eye. The left and right didn’t know what the other was doing. On a third experiment, a young patient was asked about who was his favorite girlfriend, with the word ‘girlfriend’ presented to the right hemisphere. He couldn’t answer verbally. His right-hemisphere has seen it, but the language processing left-hemisphere remained unaware. Then, using his left hand (which is controlled by the right-hemisphere, but I’m pretty sure you know that by now), the boy spelled LIZ with the letter tiles in front of him. There is no doubt that the right-hemisphere is experiencing the world but it cannot communicate verbally, only by controlling the left hand.
Despite the impressive effects of splitting the brain through callosotomy, researchers have reported that the patients involved in the studies never expressed feeling anything less than whole, that is, they would still have a unified sense of self. The hemispheres didn’t miss each other in some sense. Further experiments were carried out where subjects were asked to explain with words actions directed and carried out by the right hemisphere. The left-hemisphere would make up a post-hoc answer to fit the situation. This observation has huge implications related with the ‘story-telling’ capacity of our brain. It is important to mention that in split-brain procedures the brain is never completely split. The sub-cortical region, a more primitive region of the brain, continues connected (or the person would become seriously impaired or even die). Patients that mastered a skill before the surgery would still be able to coordinate the hands for the task, for example a fisherman would still be able, with no apparent difficulties, to tie a fishing line (it is coordinated by deeper sub-cortical levels of motor control), but when introduced to less familiar tasks, he would have a hard time to complete them. There are other clinical cases where the self seems to malfunction spectacularly. In Cotard Syndrome, for instance, the victims believe they do not exist, even though they admit having a life history, or in ‘Dissociative Identity Disorder”, the person seems to harbor multiple selves, each with its own name, memory and voice.
There is still a long way to go until science is capable to clearly describe the self, determine where it is ‘created’ in the brain, how it can survive radical surgical procedures like in split patients, how it can change completely in some cases and how this not-so-apparent illusion shapes our very perception of reality and influence the consciousness in creating the narrative of our life. Consciousness is, without a doubt, a mysterious entity and I believe that the self is itself something that exists as long as there is consciousness to be aware of it, it cannot exist independently of a brain, and it is therefore not real, an illusion. But like our thoughts, sensations, emotions, it is a product of the chemistry of the brain and there is only consciousness at the end to be aware of all of that. The stream of consciousness is all there is, and even if you suffered a serious amnesia or your psychology was replaced by Donald Trump’s, you would still have consciousness. But would you still be You?
- David Wolman. 2012. The split brain: a tale of two talves. Nature 483,260–263;
- Jim Holt. 2014. Is there such thing as a self? Prospect Magazine;
- Sam Harris. 2012. The Illusion of the Self: An Interview with Bruce Hood.
Buddhism and Modern Psychology by Robert Wright, Princeton University