Barking up the wrong free: readiness potentials reflect processes independent of conscious will
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Volition
Barking up the wrong free: readiness potentials reflect processes independent of conscious will Alexander Schlegel · Prescott Alexander · Walter Sinnott-Armstrong · Adina Roskies · Peter U. Tse · Thalia Wheatley
Received: 24 May 2012 / Accepted: 5 March 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract In the early 1980s, Libet found that a readiness potential (RP) over central scalp locations begins on average several hundred milliseconds before the reported time of awareness of willing to move (W). Haggard and Eimer Exp Brain Res 126(1):128–133, (1999) later found no correlation between the timing of the RP and W, suggesting that the RP does not reflect processes causal of W. However, they did find a positive correlation between the onset of the lateralized readiness potential (LRP) and W, suggesting that the LRP might reflect processes causal of W. Here, we report a failure to replicate Haggard and Eimer’s LRP finding with a larger group of participants and several variations of their analytical method. Although we did find a between-subject correlation in just one of 12 related analyses of the LRP, we crucially found no within-subject covariation between LRP onset and W. These results suggest that the RP and LRP reflect processes independent of will and consciousness. This conclusion has significant implications for our understanding of the neural basis of motor action and potentially for arguments about free will and the causal role of consciousness. Keywords Readiness potential · Libet · Volition · Consciousness · Free will A. Schlegel (*) · P. Alexander · P. U. Tse · T. Wheatley Department of Psychological and Brain Sciences, Dartmouth College, HB 6207 Moore Hall, Hanover, NH 03755, USA e-mail: [email protected] W. Sinnott-Armstrong Philosophy Department and Kenan Institute for Ethics, Duke University, Box 90432, Durham, NC 27708, USA A. Roskies Department of Philosophy, Dartmouth College, HB 6035 Thornton Hall, Hanover, NH 03755, USA
Introduction Although our conscious will appears to cause our actions, Benjamin Libet’s experiments raised doubts about this apparent causal connection (Libet et al. 1983). Libet and colleagues had subjects make simple motor movements, such as lifting a finger, while they measured a particular EEG marker of brain activity time-locked to the motor act. This marker—a negative potential over central scalp locations that develops in the seconds before participants make self-initiated movements—has been dubbed the “readiness potential” or RP (also known as a ‘Bereitschaftspotential’ or BP; cf. Kornhuber and Deecke 1965). Libet and colleagues estimated the earliest time of conscious awareness of a will to move by asking subjects to recall where a rotating spot on a clock face had been at the moment when they had first become aware of an urge to move. They found that the RP occurred on average 350 ms before the reported time of awareness (W). This finding has been replicated many times (e.g., Fried et al. 2011; Haggard and Eimer 1999; Lau et al. 2007; Sirigu e
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