I read about an experiment in which the researcher could predict which finger a test person would raise at a given signal. Already before the test person was conscious about which finger to raise, the researcher could tell by the image of the test person's brain (which can be obtained from an MRI- or PET-scan of the brain) finger it would gonna be.
Is there a way of behavior for the test person so the researcher can't predict which finger the person is gonna stick up?
For example, could this be possible if the test person relates his choice to the ticking of the clock in the research room? By which I mean that when the experiment starts, the person under investigation can look at the seconds showing finger (how appropriate in this experiment!) and at each tick, he or she thinks of the next finger on his hands (starting with a by the person predetermined finger and going from the left to the right or vice-versa). When the signal sound he raises the finger which he has in mind at that moment.
This doesn't change the goal of the experiment which is if one can predict which finger someone raises.