The Atheist's Guide to Reality_ Enjoying Life Without Illusions - Alex Rosenberg [72]
Libet’s results have been replicated many times, employing ever greater improvements in the technology for recording what happens in the brain, where it happens, and when it happens. There is greater accuracy in measuring the delay between the start of the button-pressing process and the occurrence of the felt act of willing. And neural measurements have been substituted for asking the subjects to report when they introspected the conscious act of will. The results pull the rug out from under introspection as a source of much knowledge about choice. They completely undercut the evidence introspective experience might give for free choice. The conscious feeling of its being entirely up to me whether I flex my wrist, and when I do so, is just irrelevant to what my body does. By the time I have the introspectively accessible feeling of deciding to move my wrist or finger, the train has already left the station. The brain has already set it in motion. The introspective feeling is too late to have anything to do with it.
The real cause of which way I point my finger (or, in the Libet experiment, the real cause of my pushing the button) is some event in the motor cortex of the brain. That event was first identified by Libet using an old-fashioned electroencephalograph taped to the subject’s scalp. Now it can be studied by newer fMRI (functional magnetic resonance imaging) machines. The fMRI machines detect the level of real-time oxygen metabolism in the specific part of the brain where the “decision” to push the button is taking place. None of the events in this part of the brain are experienced at all. They are just the results of other, earlier nonconscious states of the brain (and its environment). These, too, are processes over which the subject has no conscious control. What’s more, the neuroscientist can bring about the neural states that cause the wrist to flex and the finger to move just by stimulating this nonconscious region of brain. And sure enough, the unconscious stimulation is followed (2/10ths of a second later) by the introspective feeling of deciding to move it.
Do these results prove that there is no free will? That would be too hasty. It doesn’t follow logically from Libet’s experiments that there is no free will. But what you certainly can’t do after reading about these experiments is trust introspection to tell us whether or not we have free will. We can’t trust introspection to tell us when we made the decision to push the button. We certainly can’t trust introspection to tell us why we made the decision we did. Introspection is so unreliable that it would be scientifically irresponsible to ever trust it about anything regarding the will.
Add together the fact that introspection is wrong about the need for a conscious decision to start the body into action and the facts about blindsight—that there is no need for conscious experience to detect sensory features of the world. Between them they show that as a middleman between sensory input and action output, conscious experience is not putting together much of a track record. It gets wrong several things that most people are certain it can’t get wrong. How should we treat its other confident pronouncements? What is there left for introspection to be reliable about? Can it be relied on to tell us much about the mind—how the mind thinks, senses, and wills?
DRIVING THROUGH LIFE WITH BOTH EYES FIXED ON THE REARVIEW MIRROR
Conscious introspection is wrong about basic facts, like the need for sensations to see things and the role of the conscious will in getting the body to do even simple tasks. It gets worse.
Introspection tells us that human sight is “now-sight.” It gives us the absolute conviction