that component of the readiness potential that precedes any conscious awareness of a wish to act. Investigations with electroencephalography suggest that it can be detected some 350 ms before the individual reports a decision to make a movement and some 550 ms before the movement occurs. The finding is controversial because it implies that behavior is instigated nonconsciously and hence that free will is illusory; the ecological validity of such experiments has also been questioned. [reported by U.S. physiologist Benjamin Libet (1916–2007)]