Ok, interesting.
http://www.eurekalert.org/pub_releas...-udi041408.php
I knew of this: "More than 20 years ago the American brain scientist Benjamin Libet found a brain signal, the so-called "readiness-potential" that occurred a fraction of a second before a conscious decision."
But I didn't know of this:
"In the study, participants could freely decide if they wanted to press a button with their left or right hand. They were free to make this decision whenever they wanted, but had to remember at which time they felt they had made up their mind. ...The researchers found that it was possible to predict from brain signals which option participants would take already seven seconds before they consciously made their decision.
...
The decision could not be predicted perfectly, but prediction was clearly above chance. This suggests that the decision is unconsciously prepared ahead of time but the final decision might still be reversible."