In the 1950s, neurology was still a young science, and there was no none cure for epilepsy. Since this disease could be life-threatening in some cases, people were willing to undergo experimental surgery in the off-chance that they'd get better. Scientists were also more than willing to remove sections of the patients' brains. Perhaps they really thought they could cure the epilepsy with minimal damage. Perhaps they just wanted to see how removing certain parts of the brain affected human cognition and behavior. There were dozens of such cases, many giving dramatic insight into how the brain worked. (These studies were casually taught in my undergraduate classes, and at the time, nobody questioned their dubious ethical nature, including myself. Today, though, I wonder where these scientists' interests really laid.)
One of these studies involved severing the corpus callosum of several dozen patients. As many of you may already know, the brain is divided into two roughly symmetrical hemispheres. The corpus callosum is the network of neurons which connect the two hemispheres. You can think of it as the telephone wire between the right and left side of your brain. The decision to sever this network wasn't completely unfounded, as earlier studies had shown that it experienced a heavy surge of activity immediately proceeding a seizure. Remarkably, the procedure did work, and patients no longer suffered from epilepsy. At the same time, there were no obvious ill effects. Patients were still able to communicate, they remembered who they were, they lost no points on an IQ test.
It took several months of study to notice that something about these patients actually was different, and although at first glance this difference appeared quiet subtle, its effects were actually quiet profound. The first study to notice weird behavior went something like this: researchers asked the patient to close his eyes, and then they placed a spoon in his left hand and asked him to describe what he felt. He was unable to do so. They then placed it in his right hand and asked the same question. He immediately responded that it was a spoon. It was as though he were aware of what was happening with his right hand, but not his left.
A similar study had a patient handle an object with both hands. They then asked him to point to a picture of that object with right hand. He couldn't. They then asked him to point to the picture with his left hand. He laughed and said that of couldn't do that, either, but seemingly off its own accord, his left hand rose and pointed to the correct image. He didn't know how he had done that. The researchers weren't sure, either, but they were getting an idea.
Other weird little inconsistencies were popping up, too. There was one patient who was only sixteen years old. Before the surgery, researchers had asked him what he wanted to be when he grew up. He admitted that he was really conflicted about it. On the one hand, he wanted to be an accountant because he was good at math and enjoyed working with numbers. On the other hand, he wanted to be a race-car driver. He'd just started to learn to drive, and he found it really engaging. After the surgery, though, he stopped saying that he wanted to be a race-car driver. When asked, he always responded that he wanted to be an accountant. Inspired by their previous studies, the researchers asked him not to say what he wanted to be when he grew up, but rather to point to a picture of it. He immediately pointed to a picture of a race-car. With his left hand. When asked why, he couldn't explain his choice.
The most dramatic case happened outside of the laboratory, though. A patient was having a heated argument with his wife, and with his right hand, he tried to hit her. With his left hand, he held his right hand back. In the end, the researchers concluded that all these patients now had two personalities. One controlled their speech and their right hand, while the other operated through images and the left hand. These corresponding to the different hemispheres of the brain. As was shown with the teenager who wanted to be a race-car driver and an accountant, these different personalities already existed in the patients, but before the surgery, they were able to communicate via the corpus callosum, leading to conflicting desires in the patients. In all of us.
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