By Tom Stafford
Originally published 7 August 2015
It is perhaps the most famous experiment in neuroscience. In 1983, Benjamin Libet sparked controversy with his demonstration that our sense of free will may be an illusion, a controversy that has only increased ever since.
Libet’s experiment has three vital components: a choice, a measure of brain activity and a clock.
The choice is to move either your left or right arm. In the original version of the experiment this is by flicking your wrist; in some versions of the experiment it is to raise your left or right finger. Libet’s participants were instructed to “let the urge [to move] appear on its own at any time without any pre-planning or concentration on when to act”. The precise time at which you move is recorded from the muscles of your arm.
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