Early Split Brain Research

In the 1970's, one of the strangest and most profound scientific and philosophical discoveries was made, rather quietly... But first we need a little bit of background: up until that point, one of the most respected theories of metaphysical personal identity was based on the work of the British philosopher John Locke, who asked himself whether there is anything that can account for the continued existence of the same person over time. Yeah, leave it to philosophers to ask these silly questions... but do try to answer that question and you'll see it's not as easy as it sounds.

Although it was almost immediately criticized, especially by David Hume and Thomas Reid, Locke's theory held sway for a few centuries. His answer was that consciousness (or memory) makes the person in the pictures of you when you were young the same as the person who is you now talking about the younger person in the pictures. If there were no memory of those early events, the person in the picture and the person today would be two different persons, and no identity would obtain. In a way, it makes sense: if you can't remember having done something, how could you be reasonably convinced that you did it? Locke's answer: you can't, it was someone else -perhaps an earlier self who no longer exists.

Now, back to the revolutionary discovery. Starting in the 70's, epileptic patients who suffered from severe seizures underwent an operation that severed the corpus callosum (this is the information superhighway that connects the left and right hemispheres of the brain). The idea was that if the seizure information was stopped from being communicated to the entire brain, there would be no more seizures, nor their subsequent aftermath. The results were a success: the seizures went bye bye... but a bizarre and unforeseen consequence arose: split brain patients developed two separates spheres of consciousness within the same skull... Yes, the finding was that there are at least two different persons living in every skull (including your own), but these persons both assume they are one and the same person because of the smooth fluidity with which they communicate below the level of conscious awareness.

The following video shows the work done in the early days of this then new kind of research, as well as some of the methodological constraints and philosophical implications to which it would eventually lead. Reality can often be way more interesting than science fiction; if you're used to thinking of yourself as one person, prepare to be divided...

For a fascinating work exploiting the philosophical implications of split brain, you should check out Derek Parfit's Reasons and Persons... It'll rock your world.