Meet your doppelganger!

An old epilepsy treatment involved cutting all the connections between the two halves of a patient's brain, to prevent seizures in one side from spreading to the other side. These patients, called "split-brain" patients, ¹ exhibited behavior that had bizarre implications for our view of consciousness, but also introduced a paradox. The paradox goes away if you invite a stranger into your head. Let me explain.

The original interesting finding in split-brain patients is that they can not integrate information across the halves of their brain. If you present one side of the brain with the number 5 (by flashing a 5 on one side of a screen), and then present the other side of the brain with the number 2 (by flashing it on the other side), the patient will not be able to add the two numbers together. However, each side of the brain does know the number. The left side of the brain contains the speech centers and can verbally report its number 5. The other side of the brain can report its number by writing it on a piece of paper. There are other setups that show the independence of the two split brain halves. For example one patient was presented with the word "Texas" at the non-verbal half of his brain, and the corresponding hand began to draw a cowboy hat. When asked why, the verbal side of his brain (which did not have access to the presented word "Texas") could only guess. It is as though there are two independent consciousnesses inside the same body, if you assume that consciousness is always present in someone speaking, writing or drawing.

But this strange conclusion comes with an immediate paradox. Split-brain patients appear socially normal. They don't appear like two minds sharing a body and wrestling with each other for control. If there is a second consciousness trapped inside, unable to talk but able to draw, wouldn't it get out, or try to make itself known in some way? The second consciousness is surprisingly docile. (There are some exceptions to this, cases where two motives do seem to fight, in patients with damage to the connection between the brain halves², but I am here focusing on the cases of split-brain patients in which this does not happen).

How can we resolve the paradox? In my earlier post on Consciousness and AI I described a model called "Saltatory Consciousness", which is important for the rest of my argument here. In that model, consciousness arises at brief instants only a few times per second, even though we perceive consciousness to exist continuously. And the post explored a thought experiment involving the swapping of souls into other brains, and concluded that the soul (if it existed and could swap), would not notice the swap, because all memory comes from the brain. The new soul would inhabit the new brain and its memories without skipping a beat. And if it swapped back, it would have no idea that any swapping had happened.

In the spirit of accepting this type of "ignorance" within a moment of consciousness to everything other than what's in physical memory, we can find a solution to the paradox of split-brain patients not experiencing their second consciousness trying to lash out and make itself known.

There is no paradox, and no need to lash out, if the split brain case is similar to the non-split-brain case. If we all have multiple consciousness. The multiple consciousness don't compete or even sense each other because consciousness is ignorant of everything except the physical, biological memory. Each of our consciousnesses, if there are multiple, share the same memories and are conscious only of the singular body - and each makes the logical fallacy that it too is singular.

So the split brain patient's newly independent consciousness doesn't lash out, because from its perspective nothing really changed after the split-brain surgery, except for each side acquiring a complementary form of hemineglect ³. The second consciousness was there all along, in other words, and of course by extension it's there in you, too.

What do you think, could it be so crowded upstairs?