Time to Lay the Libet Experiment to Rest: Commentary on Papanicolaou (2017)
Psychology of Consciousness: Theory, Research, and Practice © 2017 American Psychological Association 2017, Vol. 4, No. 3, 324–329 2326-5523/17/$12.00 http://dx.doi.org/10.1037/cns0000124 COMMENTARY Time to Lay the Libet Experiment to Rest: Commentary on Papanicolaou (2017) John F. Kihlstrom University of California, Berkeley For more than 30 years, “the Libet experiment” has inspired and dominated philosoph- ical and scientific discussions of free will and determinism. Unfortunately, this famous experiment has been compromised by a serious confounding variable (i.e., there has been no control for watching the clock), and the method of data collection ignored conscious mental activity that occurred prior to the decision to act. Because Libet’s results appear to be wholly an artifact of his method, his experiment should be discounted in future discussions of the problem of free will. Keywords: agency, consciousness, free will, Libet experiment, readiness potential For more than 30 years, an experiment by In his experiment, Libet and his colleagues Benjamin Libet, a psychophysiologist interested asked subjects to perform a simple spontaneous in psychoanalytic theory, has inspired and dom- motor activity, flicking a finger or flexing a inated discussions of free will and conscious wrist, while watching a fast-moving clock, and agency. Starting with Libet, Wright, and Glea- to note the time at which they decided to make son (1982), Libet capitalized on an electroen- the movement (Libet, 1985; Libet, Gleason, cephalographic (EEG) signature known as the Wright, & Pearl, 1983; Libet et al., 1982). Ex- readiness potential (RP, or Bereitschaftspoten- amining the EEG data, they observed that the tial in the original German; Kornhuber & RP began approximately 350 ms before subjects Deecke, 1965, 1990), a negative shift in voltage decided to make the movement—which, in turn, which occurs prior to voluntary muscle move- occurred about 200 ms before the movement ments—somewhat in the manner of an event- began.
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