In the 1980s, a series of experiments by Benjamin Libet generated new interest in the topic of free will. Libet tried to measure the brain activity that accompanied a voluntary decision to make a hand movement.

Libet told research participants to move their hand whenever they wanted and to report the exact time they did so. He was simultaneously recording EMG signals from their arm muscles and EEG signals from their brains.

Illustration of a participant attached to an EMG with an EEG cap in a Libet experiment