by Ali Emerson
Have you ever used the phrase ‘I’m in two minds about it’? Well, as it turns out, that may be truer than you realise. But exactly who ‘you’ are is a very tricky question.
Your brain is divided into two parts or hemispheres. The left hemisphere controls the right side of your body and vice versa. These hemispheres communicate using a thick bundle of fibres, called the Corpus Callosum. Back in the 1940s, doctors began to cut the corpus callosum as a treatment for severe epilepsy; this procedure can be very effective and is still performed today. However, when the Corpus Callosum is severed, we observe some very strange effects.
Vicky had her brain split in order to prevent life-threatening seizures. She no longer has seizures, but she does have other problems. Often when she reaches her right hand to grab an item off the supermarket shelf, her left hand will fight to put it back. Similar challenges occur when she tries to get dressed. But what exactly is happening here? Who is fighting who?
Well, it turns out that experiments with ‘split-brain’ patients show that the left and right hemispheres can function independently. The part of the brain controlling language is in the left hemisphere. If we show a word to only the patient’s right hemisphere and ask the patient to say what he has seen, he can’t answer, as the right hemisphere has no language capability. The patient’s right hemisphere can control the left hand, however, and take the corresponding item out of a bag. If you then ask the patient why he is holding the object, you force the language centre in the left hemisphere to take over. Because the left hemisphere is unaware of what the right hemisphere saw, the patient will appear confused and will make up a plausible answer as to why he has the object.
So, it appears that the left side of your brain doesn’t know the right side is there and will try to explain away things that the right side does. And the right side can express its dislike of the cereal your left side chooses at the supermarket. Which implies that you have two separate ‘minds’ inside your head. So which ‘mind’ is you?