The Atheist's Guide to Reality_ Enjoying Life Without Illusions - Alex Rosenberg [71]
It’s not just people with brain damage that manifest these abilities. Normal-sighted subjects show the blindsight ability to discriminate visual stimuli without having the visual experience. This happens when researchers temporarily disturb their primary visual cortex by directing a strong magnetic field at it. Moreover, interfering with other parts of the brain have revealed the existence of hearing without the introspection of acoustical sensations, and touching without the consciousness of any tactile experiences.
The take-home lesson of blindsight is obvious: introspection is highly unreliable as a source of knowledge about the way our minds work. After all, what could have been more introspectively obvious than the notion that you need to have conscious experiences of colors to see colors, conscious shape experiences to see shapes, and so on, for all the five senses? Yet that turns out to be just wrong. If it’s wrong, what else that introspection insists on could turn out to be wrong?
WILLPOWER WITHOUT THE WILL?
It’s introspectively obvious that deliberate actions are the result of conscious decisions that we make. That couldn’t be wrong, could it? Many people who recognize that physics rules out free will have weighed that fact against their introspective feeling that choice is up to them. And they have decided that introspection trumps science, even 500 years of it.
Their line of thinking goes like this: Point your right index finger straight up in front of you. Now ask yourself, “Given the whole history of the universe that led up to the current state of my brain, plus all the laws of nature, known and unknown at work in my brain, is it really still up to me to choose which way to point my finger, to my left or to my right, or neither?” Science answers no. Introspection answers yes. We just know from the inside that it’s entirely up to us which way we point our index finger. We can feel it. Introspection trumps science.
Too bad for introspection. There is a series of experiments going back about 50 years now that shows conclusively that the conscious decisions to do things never cause the actions we introspectively think they do. The conscious decisions happen too late in the process to even be involved in the choosing. The most famous of these experiments was conducted by Benjamin Libet in the late 1970s (and replicated many times since). The implications of his experiments are obvious. Ever since, defenders of free will have been twisting themselves into knots trying to wriggle out of them.
Libet set up a simple task: Subjects are asked to push a button whenever they wish. They’re also asked to note the instant they “decided” to push the button—when they “felt” the conscious act of “willing” their wrist to flex, pushing the finger down on the button. At the same time, the subject’s brain is wired up to detect the activity of the part of the brain, the motor cortex, that is responsible for sending the signal to the wrist to flex, pushing the finger down. On average, it takes 200 milliseconds from conscious willing to wrist flexing and finger pressing. But the cortical processes responsible for the wrist flexing start 500 milliseconds before the button is pressed. In other words, wrist flexing is already set in motion, and everything needed to complete it has already taken place 300 milliseconds before the subjects are conscious of “deciding” to flex the wrist and press the button.
The obvious implication: Consciously deciding to do something is not the cause of doing it. It’s just a downstream effect, perhaps even a by-product, of some process that has already set the action in motion. A nonconscious event in the brain is the “real