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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

John Ostrowick, School of Computer Science,University of the Witwatersrand,

Johannesburg,South Africa.

jon@cs.wits.ac.zahttp://www.cs.wits.ac.za/~jon

Paper at:http://www.cs.wits.ac.za/~jon/opinion/libet

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Benjamin Libet (1985) has provided neurological evidence thatagents lack free-will except under special circumstances where theagent in question “changes her mind”. This paper discusses Libet’sinterpretation—that the ability to change ones mind indicates thatfree-will may yet be possible—and the conclusion is drawn that itmay be inconsistent for Libet to do so, because it does seem as if hehas provided strong evidence against the reality of free-will. Furtherevidence and criticisms of Libet’s work is discussed, and theseobjections are dealt with.

Abstract

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Libet: Timed wrist-flexing act (A), RP (“readiness potential”—brainvoltage change before action), motor cortex signal (M), and feelingas of wanting to act (W) compared to moving spot on a CRT. Controlstimulus S—on the skin—was used to ensure accuracy of timing ofW. Also measured V (veto, change of mind) timing.

Grey Walter: Wired RP-detecting electrodes to slide changer, gavesubjects dummy slide button. No control stimulus. Slide changedwhen RP initiated. (We mention this experiment because itcorroborates Libet’s results).

The experiments

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Libet: A occurred at 0.0 sec. M occurred at approx. -0.2 sec. W occurred atapprox -0.2 sec. RP occurred at approx. -0.55 sec. V occurred at -0.15 sec. Heconcluded that RP caused actions, not W (wanting to perform the action). Theonly room for free-will is V.

The results

“It was concluded that cerebral initiation of a spontaneous voluntary act beginsunconsciously. However, it was found that the final decision to act could still beconsciously controlled during the 150 ms or so remaining after the specificconscious intention appears.” (1985, p529)

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Grey Walter: Subjects reported that slide show device had a bizarreprecognition; it read their minds and changed the slide before they haddecided to change the slide.

Näätänen: Similar experiment, confirmed Libet’s results, even forspontaneous unplanned actions.

The results

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

• We normally think it is our conscious choices that make us do what we do:

• But Libet is saying:

Why this may be worrying

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

• But if that’s all he’s saying, then W could contribute to the action orpartially cause it; and he did find that actions could be vetoed. For this to bereally a problem, this would have to be the case:

Why this may be worrying

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Amongst various problems, the most salient three are as follows…

• Does W contribute causally to A, or is it causally inefficacious? If Libet isworried about W being causally inefficacious, what is his evidence for this? Itmay be that RP is necessary but not sufficient for A.

• What if RP is caused by antecedent reasoning and planning, so that theagent in question is “primed” to act? Just because your actions are ultimatelycarried out nonconsciously, does not mean they were not freely chosen inaccordance with rational goals beforehand.

• Why is Libet worried that W, qua mental is not causally efficacious, but hethinks that V is?

Vetoes and problems: 1

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

• Libet says, and I quote:

• But then he says:

Vetoes and problems: 2

“It might be argued that unconscious initiation applies to the kind of spontaneous but perhaps impulsive voluntaryact studied here, but not to acts involving slower conscious deliberation of choices of action. ... Even when amore loosely defined conscious preplanning has appeared a few seconds before a self-initiated act, the usualspecific conscious intention to perform the act was consistently reported as having been experienced separatelyjust prior to each act by all subjects... This leads me to propose that the performance of every conscious voluntaryact is preceded by special unconscious cerebral processes...” (Libet, 1985, p536).

“Would the appearance of a conscious trigger or veto also require its own period of prior neuronal activity, asis postulated for the development of the conscious urge or intention to act and for a conscious sensoryexperience? Such a requirement would imply that conscious control of the volitional outcome, whether byveto or by an activating trigger, is itself initiated unconsciously. For control of the volitional process to beexerted as a conscious initiative, it would indeed seem necessary to postulate that conscious controlfunctions can appear without prior initiation by unconscious cerebral processes, in a context in whichconscious awareness of intention to act has already developed” (p538, ibid.)

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Q: Does W contribute causally to A, or is it causally inefficacious? If Libet isworried about W being causally inefficacious, what is his evidence for this? Itmay be that RP is necessary but not sufficient for A.

A: Libet believes W is epiphenomenal. Furthermore, W appears simul-taneously with M, so W could not causally contribute to M. Therefore A iscaused nonconsciously

Solving the problems: 1

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Q: What if RP is caused by antecedent reasoning and planning, so that theagent in question is “primed” to act? Just because your actions areultimately carried out nonconsciously, does not mean they were not freelychosen in accordance with rational goals beforehand.

A: This is a legitimate concern. Libet’s answer is:

Solving the problems: 2

“Some may view ... free will as operative only when voluntary acts follow slower conscious deliberation...But ... any volitional choice does not become a voluntary action until the person moves”. (ibid., pp538-9).

Libet(2001) argues that it is not that chain of reasoning which is causally efficacious in moving thebody—at least not directly—but rather it is the “act now” event which ultimately causes the act (p61).Libet’s argument in defense of this view is simple: We can muse and reason all day, even taking decisionsabout what we will do, but never actually act (Libet, 1985, pp538-9). It is only when we experience the“act now” kind of decision that our body actually does something.

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

Q: Why is Libet worried that W, qua mental is not causally efficacious, but hethinks that V is?

A: This is inconsistent. Either both must be epiphenomenal or neither. Hisevidence in fact indicates that V is epiphenomenal as well because V occursafter M (M is at -0.2 sec and V is at -0.15 sec), therefore V cannot contributeto action because it has already been initiated by M.

Solving the problems: 3

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LibetLibet’’ss Experiments and Free-Will: Implications Experiments and Free-Will: Implications

• Libet should, as a materialist, postulate that there is an antecedent brainevent to explain V. He found (1982) that all mental states are preceded bybrain events occurring 0.2 sec before. Thus:

Solving the problems: 3