Red Pill Or Blue Pill: Humans Have Free Will, Even If Computers Can Predict Our Readiness Potential

Readiness potential
Our ability to veto movements even after the brain displays readiness potential proves humans have free will, new study says. Philip Taylor CC BY-SA 2.0

How much of our will is free and under our control — and how much of it is just our brain making predetermined decisions for us? Researchers at the Charité's Bernstein Center for Computational Neuroscience decided to investigate the limitations of our free will by pitting humans against computers.

The study, published in the Proceedings of the National Academy of Sciences, looked at a specific brain activity pattern called "readiness potential," which occurs before every choice you make. The researchers set out to answer "whether people are able to cancel movements after the elicitation of such [readiness potentials], and if so, until which point in time." To do this, they pitted humans against computers in a simple game.

Human vs. Computer

The game required the human participants press a button with their foot, while the computer had to guess when this small action would occur. Each time it guessed participants were going to push the button, the computer would send up a stop signal in the form of a red light. If participants continued past the stop signal and pressed the button, they'd lose points. But if they managed to press the button without alerting the computer, they'd gain points.

Of course there was a catch: Participants wore EEG hats designed to give the computer an advantage in checking readiness potential and correctly guessing when participants were about to press the button. Since readiness potential occurs less than a second before a person makes a decision, the researchers wanted to find out whether or not a person could "veto" their movements — essentially not press the button even if their readiness potential says they are about to.

The researchers knew that when a person thinks about making a move before eventually making it — also known as when the human brain goes on autopilot — the readiness potential would be easy for the computer to spot. They anticipated, then, the computer would win every trial.

However, the computer did not win every time as the participants were able to veto their movements — but only up until a certain point.

When the computer flashed the stop signal earlier than 200 milliseconds, the participants were able to stop their movements and win the match. Yet, the researchers soon discovered 200 milliseconds was the point of no return. If participants saw the stop signal later than that, they ended up pressing the button and losing.

After telling participants to move randomly in order to avoid being detected by the computer, the researchers observed the shape of the readiness potential (as described by the EEG) to be the same as all other times, ultimately allowing the computer to detect and send up a stop signal. This suggests that even when we want to act randomly, our brain won't let us.

While previous research has demonstrated free will does indeed exist, there's always been some contention. The apparent ability to veto a movement, even after displaying readiness potential, means we humans do control our actions…if only so far.

Source: Schultze-Kraft M, et al. The point of no return in vetoing self-initiated movements. Proceedings of the National Academy of Sciences. 2015.

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