People have been told time and again that they have free will. But do they? Researchers have sought to resolve the question by studying decision-making processes related to voluntary movements and found that people do have control over their decisions, at least until a certain point.
Published in the Proceedings of the National Academy of Sciences, the study built upon the debate on determinism that has been raging on since at least the 1980s. Benjamin Libet demonstrated then that conscious decisions are initiated by unconscious processes in the brain, and that "readiness potential," a wave of activity in the brain, could be observed before a subject actually makes a decision.
Unconscious brain processes appearing to predict decisions before they are made were considered as proof of determinism, a doctrine that free will is merely an illusion. As such, there is no "conscious self" making the decision.
Taking a stab at the issue, John-Dylan Haynes and colleagues turned to state-of-the-art techniques to test whether or not people will be able to stop planned movements when the readiness potential has already been triggered.
As part of the study, subjects were tasked to have a "duel" with a computer. Their brain waves were then monitored for the duration of the activity with electroencephalography (EEG). On the computer side of things, a machine was specially trained to predict when a subject would move based on their EEG data, aiming to out-maneuver the individual.
Based on their results, the researchers proved that people were able to intervene in the decision-making process and interrupt a movement to show they are not at the mercy of early and unconscious brain waves.
"Previously, people have used the preparatory brain signals to argue against free will. Our study now shows that the freedom is much less limited than previously thought," said Haynes.
However, the researchers also discovered a "point of no return." When this point is reached during the decision-making process, canceling a movement will no longer be possible.
Other authors for the study include Matthias Schultze-Kraft, Benjamin Blankertz, Daniel Birman, Sven Dahne, Marco Rusconi, Kai Gorgen and Carsten Allefeld.
Photo: J E Theriot | Flickr