Here's something a bit funny. We're told that people's decisions can be predicted by brain scan several seconds before the people think they've made a conscious decision. John Dylan-Haynes, one of the researchers, says: "Our decisions are predetermined unconsciously a long time before our consciousness kicks in". What is the evidence that the study provided for this interesting claim? According to the New Scientist's summary: "By deciphering the brain signals with a computer program, the researchers could predict which button a subject had pressed about 60% of the time – slightly better than a random guess." (The choice is a binary one.)
So the claim which the data supports is that several seconds before the subject thinks she's made a choice, the brain is in a state that makes one of the choices somewhat more likely than the other. Now, we can ask: Which of two hypotheses does this data support better?
- Our decisions are predetermined unconsciously a long time before our consciousness kicks in.
- Unconscious factors a significant amount of time before the conscious decision indeterministically affect the likelihood that we will consciously make one decision rather than another.
It's worth noting that in ordinary situations where we ordinarily take people to have free will, we are often able to predict people's decisions with much better than 60% probability. This isn't to denigrate the brain-scanner. The case here is of a binary choice between button pushes, and our own accuracy would probably be fairly poor. Still, it would be fun to compare the brain-scanner against the accuracy in prediction by a researcher looking through a one-way mirror, seeing which button the person gazes towards, etc.
All that said, I actually have little problem with claim (1): I am not aware of a good argument that freedom (even of the libertarian sort) requires that one be aware of the decision when one makes it. In fact, if anything, it fits better with my preferred model of free will to have the awareness of the decision be explanatorily and maybe even causally posterior to the decision.