The name of my lab during my fellowship at NIH 20 years ago was the Human Motor Control Section, and it used various electrical tools to study the physiology behind human movements. I was never a gadget person, so the tangle of monitors, colored cords, amplifiers, and alligator clips felt, at times overwhelming. But one test was simple enough: eliciting the Bereitschaftspotential or the “Readiness Potential (RP)” through electroencephalogram (EEG).

The standard view of voluntary action is intuitive: A person forms a conscious intention to move, then the brain issues the command to execute it.

That naturally led to a simple question: Is there a brain signal preceding the movement in the motor cortex (and other brain areas responsible for movement)? Wouldn’t that signal represent the brain’s intention and command to move?

We connected ourselves to EEG electrodes and voluntarily contracted the same muscle; for example, by pinching our fingers. EEG usually detects dramatic cortical events like seizures, so an individual finger pinch didn’t visibly alter the trace. But if we added recordings from multiple attempts, say 100 times, a slow, negative signal appeared over the motor cortex and supplementary motor area, beginning one to two seconds before the movement. While it is difficult to know what this signal truly represented, activity was happening in the motor area of the brain before the movement, and this signal was named the RP.

In 1983, Benjamin Libet did a series of experiments to further understand the relationship between our intention to move and RP. He had subjects flick their finger spontaneously without any cue, while watching a special clock that circled every 2.6 seconds. They were then asked to report the moment they first became aware of their intention to move. Libet called this time W time, for “willing.”

As expected, the RP appeared before the movement. But more provocatively, the RP began before the W, the reported moment of conscious intention, by several hundred milliseconds. Libet interpreted this to mean that the brain initiates voluntary actions before we consciously decide, and so an obscure scientific experiment sparked a large and heated debate involving philosophers and popular media about the existence of

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