Can one brain have two minds?

Imagine a knife slicing down right in the middle of your brain and splitting it into two separate halves. This is the result of a corpus callosotomy.

A summary of the functions for the left brain and right brain

The brain is commonly believed to be split into the left hemisphere, the logical side, and right hemisphere, the artistic side. These two halves are usually joined together by the corpus callosum, a fibre tissue that allows internal communication between the halves. However, people with refractory epilepsy or some traumatic accidents have the corpus callosum removed as a treatment and this creates a split brain.

There have been researches such as the one conducted by Roger Sperry that have proven the isolation of each half of the brain. This led to the proof that each hemisphere will have its own perception and impulses to act. Additionally, there have been cases where people with a split brain have reported conflicts in their lives. For instance, when one split-brain patient dressed, he sometimes pulled his pants up with one hand and down with the other due to the conflicting actions in each half of the brain. Luckily, conflicts like this seldom occur and even if a conflict does appear, one hemisphere usually takes control over the other half.

These results leave a lot of researchers questioning, do split-brain patients have two minds? Imagine having the one side of the brain deciding to punch someone with your left hand and the half of the brain controlling the right-hand tries to stop the action.

A study in 2017 found strong evidence against the split conscious theory. Yair Pinto and his team conducted a series of tests on two patients. In one of the tests, the patients were placed in front of a screen and shown various objects displayed in several locations. The patients were then asked to confirm whether an object appeared and to indicate its location. In another test, they had to correctly name the object they had seen, a notorious difficulty among spit-brain patients.  One of the patients went through all the tests using only his right visual field and the other patient only used his left visual field. Shockingly, the results have proven the unity of the two brains since the patients were able to respond correctly by using their left hand, right hand, or verbally. However, the experiment has not been replicated yet due to the difficulty in finding participants.

This new finding led to a new debate between the scientists regarding the existence of two separate minds in one brain. Here is a full video of the long debate on September, 18,2018 between Elizabeth Schechter, who stands for the two-mind view starts her explanation at 9:26, Yair Pinto, who debates for the one-mind view starts his point of view at 25:00, and Joseph Ledoux, who has an intermediate view starts at 47:27, (uploaded by NYU Center for Mind, Brain and Consciousness).

In all, even though the answer to this question is still undetermined. If the existence of two minds in one brain is proven, this leads to the question of, are we really the individual we think we are or is there someone else living within us?

– Eric Ma