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readiness potential

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A negative event-related potential, across wide areas of both frontal lobes, the motor cortex, and the parietal lobes of the cerebral cortex, gradually increasing for approximately a second to two seconds before a person performs a voluntary action at a time of his or her own choosing. The phenomenon, revealed by averaging the EEG traces across a number of voluntary actions, was discovered in 1964 by the German neurologist H(ans) H(elmut) Kornhuber (born 1928) and his postgraduate student Lüder Deecke (born 1938) and published in the journal Pflügers Archiv (European Journal of Physiology) briefly in 1964 and at length in 1965. It is usually interpreted as an electrophysiological sign of planning, preparation, and initiation of voluntary action, and it has been replicated with a variety of bodily actions, including flexing a finger or wrist, moving a foot, and vocalizing a syllable. It suggests that voluntary decision processes occupy more than a second, which contrasts with the much shorter reaction time for automatic responses to stimuli. According to research by the US neurophysiologist Benjamin Libet (1916–2007) published in the journal Behavioral and Brain Sciences in 1985, conscious decisions lag 350 to 400 milliseconds behind the onset of the associated readiness potentials, suggesting that spontaneous voluntary action begins unconsciously and apparently undermining the conventional interpretation of free will. See also Libet's delay. Compare contingent negative variation. RP or BP abbrev. [Translated from the German Bereitschaftspotential, the term introduced by Kornhuber and Deecke]

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