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17 Mar 09

Unconscious decisions

Benjamin Libet’s experimental finding that decisions had in effect already been made before the conscious mind became aware of making them is both famous and controversial; now new research (published in a ‘Brief Communication’ in Nature Neuroscience by Chun Siong Soon, Marcel Brass, Hans-Jochen Heinze and John-Dylan Haynes) goes beyond it. Whereas the delay between decision and awareness detected by Libet lasted 500 milliseconds, the new research seems to show that decisions can be predicted up to ten seconds before the deciders are aware of having made up their minds. (Conscious Entities)

www.consciousentities.com/?p=64 - Preview

freewill Libet consciousness neuroethics cogsci

Whereas the delay between decision and awareness detected by Libet lasted 500 milliseconds, the new research seems to show that decisions can be predicted up to ten seconds before the deciders are aware of having made up their minds.
In the SMA the researchers found activity which predicted the decision some five seconds before the moment of conscious awareness, but it was elsewhere that the earliest signs appeared - in the frontopolar cortex and the precuneus. Here the subject’s decision could be seen as much as seven seconds ahead of time: allowing for the delay in the fMRI response, this tots up to a real figure of ten seconds.
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- The researchers suggest the results do three things: they show that the delay is not confined to areas which are closely associated with motor activity, but begins in ‘higher’ areas; they demonstrate clearly that the activity relates to identifiable decisions, not just general preparation; and they rule out one of the main lines of attack on Libet’s findings, namely that the small delay observed is a result of mistiming, error, or misunderstanding of the chronology.
- further research into decisions made in more real-life circumstances
- I think making a decision and becoming aware of having made that decision are two different things, and I have no deep problem with the idea that they may occur at different times. The delay between decision and awareness does not mean the decision wasn’t ours, any more than the short delay before we hear our own voice means we didn’t intend what we said.

Benjamin Libet - Libet's short delay.

The experiments carried out by Benjamin Libet into the timing of conscious awareness (briefly described here ) have provoked, and go on provoking, a vast amount of discussion. His own theory of consciousness as a kind of field has received somewhat less attention; and the strange brain-cutting experiment he proposed to test it seems likely to remain unperformed for the foreseeable future. A large number of papers and discussions have been published: in 2004, Libet finally summarised his own account in the book 'Mind Time'. (consciousentities.com)

www.consciousentities.com/libet.htm - Preview

freewill Libet consciousness mind neuroethics cogsci

whatever the voltage or frequency of the
pulses, the stimulus had to persist for about 500 milliseconds before the
subject became consciously aware of it.
But we also respond to
events, and here a delay is highly relevant and noticeable.
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- our unconscious responses are far quicker than
  our conscious ones
- Libet's hypothesis was that conscious awareness is
  subjectively referred backwards in time. We consciously perceive the
  stimulus as occuring at the same
  moment it registers unconsciously, even though it doesn't in fact enter our awareness
  until it has persisted for half a second. Subjectively we backdate it to match
  the EP at the beginning rather than the end of the 500
  millisecond span.
- Perhaps the
  sensations actually enter conscious awareness immediately, and the
  half-second delay merely allows time for them to become reportable, or
  fixed in short term memory? Perhaps we are merely dealing with the
  difference between being aware of the stimulus, and being aware that we
  are aware of it? Libet contends that awareness and memory, especially
  declarative, explicit memory, are different and independent
  phenomena.
- the perceived time at
  which we make a decision must also be subjectively referred back by 500
  milliseconds. Unlikely as it seems, and contrary to our own impression, we
  must have made our decisions slightly before we actually become aware of
  them.
- This 'Readiness Potential' or
  RP appeared about 800 milliseconds in advance of the act, and seemed to be
  a clear indication that the intention to act had formed.
- the RP appeared some 500 milliseconds before the reported
  awareness of a decision to move
- free will was a delusion
- Although the subject's decision to move occurred too early for it
  to have been initiated by conscious thought, there was still - just - a
  window of opportunity in which conscious awareness might conceivably veto
  the move.
- Is the RP really a signal
  that a decision has been made?
- Might not the RP merely signal a
  quickening of attention, rather than a moment of decision?
- isn't it possible that we need a certain amount of
  time just in order to report the awareness to
  ourselves?
- his proposed CMF is an emergent phenomenon: something that arises from
  the combination of active neurons but amounts to something distinctively
  more than, and different from, the sum of brain activity.

16 Mar 09

Exposing some holes in Libet's classic free will study

"The results reported here have implications for the whole tradition of having participants locate temporally subjective events using the clock paradigm," the researchers concluded.

bps-research-digest.blogspot.com/...e-holes-in-libets-classic.html - Preview

Libet freewill neuroethics

22 Apr 08

Not Exactly Rocket Science : Unconscious brain activity shapes our decisions

Our brains are shaping our decisions long before we become consciously aware of them. That's the conclusion of a remarkable new study which shows that patterns of activity in certain parts of our brain can predict the outcome of a decision seconds before we're even aware that we're making one. (myTetraCell)

scienceblogs.com/...ivity_shapes_our_decisions.php - Preview

decision-making neuroscience grue Libet freewill

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