Further practical findings which relate to human consciousness
An interesting early experiment was due to William Grey Walter. He had a patient whose brain was exposed (in those days, brain surgery was often conducted under local anaesthesia only; the brain itself has no feeling). Walter was showing the patient a slide show, a series of pictures which could be advanced from one to the next by a carousel mechanism. He told the patient that when he was tired of looking at one picture, he could move to the next by pressing a button. Unknown to the patient, the button did nothing, and the carousel mechanism was connected to part of his brain. He reported to Walter that ‘as soon as I decide to look at another picture, the machine advances to it. I never have to press the button!’ Clearly, the decision in the patient’s brain drove the machine.
Practical brain surgeons often learned a lot about how brains are organized. Thus, some areas seemed to be a store or gatekeeper for memory. If touched, they might elicit a specific memory from the patient; touched again, they might elicit a different one. That specific area seemed to be packed with so densely with memories that the surgeon’s touch was not precise enough to trigger any one of them repeatedly. Other areas of the brain were ‘silent’ and elicited nothing from the patient. They might have been concerned with other brain activities, or perhaps with internal administrative matters (such as the calcium/ magnesium ratio of the blood) that never reach conscious attention.
The experimental neurologist Benjamin Libet26 took Grey Walter’s early experiment further. He explored the cerebral response to voluntary wrist movements, and reckoned that detectable intentions arise in the brain before we are conscious of them. His findings seem to imply that we are all robotic zombies driven by pure mechanism. Our consciousness is a mere passive observer (‘a kibitzer’, as I like to call it) that tags along behind, sees whatever the body does, and maintains the back-dated illusion that it is in control. In reality,our awareness is always a bit behind what we are up to, and is deluding itself. Libet has even measured the length of delay, and makes it a trifle under half a second. He suggests that it gives the brain time to organize a coherent sensory experience out of the frequently distorted input from the senses. Most of the time, of course, we want a true picture of the world around us. But if that picture is too unpleasing, the brain has time to construct a hallucination (I discuss hallucinations in Chapter 10). We habitually back-date our sensory awareness to eliminate that half-second delay.
Libet reckoned that his findings supported the freedom of the will. That half-second between an intention and a conscious awareness of action gives the mind a chance to ‘veto’ the action. Hence, argued Libet, we do not merely have an illusory sense of free will: we really have it.
