Many philosophers and scientists have argued that free will is an illusion. Unlike all of them, Benjamin Libet found a way to test it.
Ben Libet, author of the most famous experiment ever done on consciousness, has died at the age of 91.
Not long before his death he wrote me a letter about my book Conversations on Consciousness. Polite and kind though his words were, his real reason for writing was, I think, to ask why he wasn't one of the interviewees. I was stung into replying immediately to tell him how much I wished he had been. The truth was that I had no resources for writing the book: I just interviewed the people I met at conferences or when giving lectures, or those near to home. Sadly, our paths never crossed while I was writing the book and there was no way I could travel to UC San Francisco especially to talk him, much as I would have loved to.
So I must be content with my happy memories of the one time we did meet, back in 1991. After a conference in Berkeley he invited me for lunch in a little Chinese restaurant and then we walked around Golden Gate Park, talking nineteen to the dozen about consciousness, mind, life, free will and the meaning of death.
And of course we talked about his famous experiment. He had, in fact, carried out lots of experiments on consciousness since the early 1970s. First there was a series of studies of the timing of neural events, showing that when you directly stimulate the brain with tiny pulses of electricity it requires about half a second of continuous stimulation of the sensory cortex for a conscious sensation to be felt.
Note the way I have worded this. It is not true to say that you need half a second of stimulation and then the sensation is felt; that would mean our experience of the world would be delayed by half a second and we'd all be dead. Instead, he proposed (and provided plenty of evidence for) the idea that sensations are subjectively antedated to the time of the initial brain effect, but are only consciously experienced if half a second of activity follows. This is the origin of what is often called "Libet's half-second delay".
This may be weird enough, but it is for his experiment on free will that he will mostly be remembered. In this experiment he wanted to find the cause of our spontaneous, deliberate actions. Certainly we feel as though we consciously decide to act and then do so. Yet philosophers and scientists for hundreds of years have argued that the brain does not need a magical conscious self to start actions off, and free will must be an illusion. Unlike all the thousands of people who have argued around this point, Libet actually found a way to test it.
He asked subjects in the laboratory to hold out their arm and, whenever they felt like it and of their own free will, to flex their wrist. He then measured three things - the time at which the movement began, the time at which the "readiness potential" in the brain began (signalling the brain starting to organise the coming movement) and then, most tricky of all, the time at which the subject made the decision to move.
This really is tricky because there is, by definition, no physical activity in the brain or anywhere else that corresponds to this. He was trying to measure something purely mental - the free decision, or thought, of wanting to act. Finding a way to do this is probably why the experiment became so famous. What he did was this. He had a spot revolving on a screen, like a clock face, and he asked the subjects to call out where the spot was at the exact moment that they decided to act. In other words, they were, after the fact, making a judgement about where the spot was at the time, and that could be used to accurately time the decision to act.
And his results? They were quite consistent and have since been repeated many times. The brain activity comes first, then the decision to act, and then finally the action itself. Not only does the decision to act happen after the brain is already getting ready to set off the action, but it comes nearly half a second later. It looks as though our conscious decision to act cannot, however strongly it feels that way, be the cause of our actions.
Oh dear! Free will seems to be disproved. But it's not that simple. Libet himself did further experiments that seemed to show that we may not be able to start actions consciously, but we can veto them once they have begun - saving at least some role for free will. But even that does not end the issue. Literally hundreds of academic articles, and several whole books, have been written about this experiment and how to interpret it. This is why I say it is the most famous experiment on consciousness ever done.
In a way the whole furore is bizarre. Most scientists claim to be materialists. That is, they don't believe that mind is separate from body, and firmly reject Cartesian dualism. This means they should not be in the least surprised by the results. Of course the brain must start the action off, of course the conscious feeling of having made it happen must be illusory. Yet the results created uproar. I can only think that their materialism is only skin deep, and that even avowed materialists still can't quite accept the consequences of being a biological machine.
Libet, unlike so many others, was wonderfully open about this. He really did believe that mind can affect body, that consciousness is some kind of power of the "non-physical subjective mind" or "conscious mental field", and even that we might consciously survive death. Indeed, this was what inspired his experiments in the first place.
What I so much enjoyed and admired, on that walk all those years ago, was his willingness to bring his science right into his everyday life, and his life into his science. As we walked along the street he explained how important free will was to him, that without it our lives would be meaningless and there would be no point in being good, because we would have no true freedom to choose between good and evil. He pointed towards a little girl up ahead of us on the pavement. His results, he said, showed that we cannot be held responsible for thinking of murdering, raping or stealing from people because initiating such actions begins in the unconscious brain, but we can and must be held responsible for stopping ourselves from doing those things. In this way his own results made moral sense.
I disagree fundamentally with him. I think, and thought then, that free will is entirely illusory. So our discussion was lively and exciting and full of the most wonderful mixture of science, philosophy and the anguish of everyday life. I would have loved to have interviewed him for Conversations on Consciousness. One of the themes I tried to bring out in those interviews was how consciousness researchers fit their work into their ordinary lives, and he was one of those rare scientists whose life and work were completely intertwined.
Sadly, I don't believe he ever read my letter, telling him how very much I would have liked to meet him again. A few days later I received an email from his daughter, Moreen, telling me that he had died peacefully on July 23, aware but weak, and with his family around him. She said "Your comments on his relating life to his work also crystallises something typical of him which was good to see described the way you did. I think that he experienced death in that way also. He was very curious about what that experience might reveal about the mind and brain issue. Perhaps he knows now."
