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Some areas of the human brain implicated in mental

disorders that might be related to free will. Area 25 refers to

Brodmann's area 25, related to long-term depression.

Neuroscience of free willFrom Wikipedia, the free encyclopedia

Neuroscience of free will is the part of neurophilosophy that studies the interconnections between free will andneuroscience. As it has become possible to study the living brain, researchers have begun to watch decision makingprocesses at work. Findings could carry implications for our sense of agency and for moral responsibility and the

role of consciousness in general.[1][2][3]

Relevant findings include the pioneering study byBenjamin Libet and its subsequent redesigns; thesestudies were able to detect activity related to adecision to move, and the activity appears to begin

briefly before people become conscious of it.[4]

Other studies try to predict activity before overt

action occurs.[5] Taken together, these variousfindings show that at least some actions - likemoving a finger - are initiated unconsciously at first,

and enter consciousness afterward.[6]

In many senses the field remains highlycontroversial and there is no consensus among researchers about the significance of findings, their meaning, or whatconclusions may be drawn. It has been suggested that consciousness mostly serves to cancel certain actions

initiated by the unconscious,[7] so its role in decision making is experimentally investigated. Some thinkers, likeDaniel Dennett or Alfred Mele, say it is important to explain that "free will" means many different things; amongthese versions of free will some are dualistic, some not. But a variety of conceptions of "free will" that matter to

people are compatible with the evidence from neuroscience.[8][9][10][11]

Contents

1 Overview

1.1 Free will as illusion

1.2 Disputed relevance of scientific research

2 Notable Experiments

2.1 The Libet experiment2.2 Unconscious actions

2.3 Unconsciously cancelling actions

2.4 Neuronal prediction of free will

3 Other related phenomena

3.1 Retrospective construction

3.2 Manipulating choice

3.3 Manipulating the perceived intention to move

3.4 Related models

3.5 Related brain disorders

3.6 Neural models of voluntary action

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A monk meditates. Human agency, the ability

to affect the surrounding world, may be a

result not so simply of conscious choice –

but instead a result of training unconscious

habits beforehand.[12]

-Patrick Haggard[6] discussing an in-depth

experiment by Itzhak Fried[13]

3.6 Neural models of voluntary action

3.7 Prospection

4 See also

5 References

6 External links

Overview

One significant finding of modern studies is that a person's brainseems to commit to certain decisions before the person becomesaware of having made them. Researchers have found delays ofabout half a second (discussed in sections below). Withcontemporary brain scanning technology, other scientists in 2008were able to predict with 60% accuracy whether subjects wouldpress a button with their left or right hand up to 10 seconds before

the subject became aware of having made that choice.[5] Theseand other findings have led some scientists, like Patrick Haggard,to reject some forms of "free will". To be clear, no single studywould disprove all forms of free will. This is because the term "freewill" can encapsulate different hypotheses, each of which must beconsidered in light of existing empirical evidence.

There have been a number of problems regarding studies of

free will.[14] Particularly in earlier studies, research relied toomuch on the introspection of the participants, but introspectiveestimates of event timing were found to be inaccurate. Manybrain activity measures have been insufficient and primitive asthere is no good independent brain-function measure of theconscious generation of intentions, choices, or decisions. Theconclusions drawn from measurements that have been madeare debatable too, as they don't necessarily tell, for example,what a sudden dip in the readings is representing. In otherwords, the dip might have nothing to do with unconsciousdecision, since many other mental processes are going on while

performing the task.[14] Some of the research mentioned herehas gotten more advanced, however, even recording individual

neurons in conscious volunteers.[13] Researcher Itzhak Friedsays that available studies do at least suggest consciousnesscomes in a later stage of decision making than previouslyexpected - challenging any versions of "free will" where

intention occurs at the beginning of the human decision process.[10]

Free will as illusion

...the current work is in broadagreement with a general trend inneuroscience of volition: although wemay experience that our consciousdecisions and thoughts cause ouractions, these experiences are in factbased on readouts of brain activity in anetwork of brain areas that controlvoluntary action...It is clearly wrongto think of [feeling of willingsomething] as a prior intention, locatedat the very earliest moment of decisionin an extended action chain. Rather, Wseems to mark an intention-in-action,quite closely linked to actionexecution.

“

”

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An activity like playing

the piano may be

intentional, but is

generally regarded as

requiring many

practiced actions.

Studies suggest that

each key press could be

initiated unconsciously.

It is quite likely that a large range of cognitive operations are necessary to freely pressa button. Research at least suggests that our conscious self does not initiate allbehavior. Instead, the conscious self is somehow alerted to a given behavior that therest of the brain and body are already planning and performing. These findings do notforbid conscious experience from playing some moderating role, although it is alsopossible that some form of unconscious process is what is causing modification in ourbehavioral response. Unconscious processes may play a larger role in behavior thanpreviously thought.

It may be possible, then, that our intuitions about the role of our conscious "intentions"have led us astray; it may be the case that we have confused correlation with causationby believing that conscious awareness necessarily causes the body's movement. Thispossibility is bolstered by findings in neurostimulation, brain damage, but also researchinto introspection illusions. Such illusions show that humans do not have full access tovarious internal processes. The discovery that humans possess a determined will wouldhave implications for moral responsibility. Neuroscientist and author Sam Harrisbelieves that we are mistaken in believing the intuitive idea that intention initiatesactions. In fact, Harris is even critical of the idea that free will is "intuitive": he sayscareful introspection can cast doubt on free will. Harris argues "Thoughts simply arisein the brain. What else could they do? The truth about us is even stranger than we may

suppose: The illusion of free will is itself an illusion".[15] Philosopher Walter JacksonFreeman III nevertheless talks about the power of even unconscious systems andactions to change the world according to our intentions. He writes "our intentional

actions continually flow into the world, changing the world and the relations of our bodies to it. This dynamic systemis the self in each of us, it is the agency in charge, not our awareness, which is constantly trying to keep up with

what we do."[16] To Freeman, the power of intention and action can be independent of awareness.

Disputed relevance of scientific research

Some thinkers like neuroscientist and philosopher Adina Roskies think these studies can still only show,unsurprisingly, that physical factors in the brain are involved before decision making. In contrast, Haggard believes

that "We feel we choose, but we don't".[10] Researcher John-Dylan Haynes adds "How can I call a will 'mine' if I

don't even know when it occurred and what it has decided to do?".[10] Philosophers Walter Glannon and AlfredMele think some scientists are getting the science right, but misrepresenting modern philosophers. This is mainlybecause "free will" can mean many things: It is unclear what someone means when they say "free will does notexist". Mele and Glannon say that the available research is more evidence against any dualistic notions of free will -

but that is an "easy target for neuroscientists to knock down".[10] Mele says that most discussions of free will arenow had in materialistic terms. In these cases, "free will" means something more like "not coerced" or that "theperson could have done otherwise at the last moment". The existence of these types of free will is debatable. Meleagrees, however, that science will continue to reveal critical details about what goes on in the brain during decision

making.[10]

This issue may be controversial for good reason: There isevidence to suggest that people normally associate a belief in

free will with their ability to affect their lives.[2][3] PhilosopherDaniel Dennett, author of Elbow Room and a supporter of

"[Some senses of free will] arecompatible with what we are learningfrom science...If only that was what

“

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-Daniel Dennett discussing science and free

will[17]

deterministic free will, believes scientists risk making a seriousmistake. He says that there are types of free will that areincompatible with modern science, but he says those kinds offree will are not worth wanting. Other types of "free will" arepivotal to people's sense of responsibility and purpose (see also"believing in free will"), and many of these types are actually

compatible with modern science.[17]

The other studies described below have only just begun to shedlight on the role that consciousness plays in actions and it is too

early to draw very strong conclusions about certain kinds of "free will". It is worth noting that such experiments – sofar – have dealt only with free will decisions made in short time frames (seconds) and may not have direct bearingon free will decisions made ("thoughtfully") by the subject over the course of many seconds, minutes, hours or

longer. Scientists have also only so far studied extremely simple behaviors (e.g. moving a finger).[18] Adina Roskiespoints out five areas of neuroscientific research: 1.) action initiation, 2.) intention, 3). decision, 4.) Inhibition andcontrol, and 5.) the phenomenology of agency, and for each of these areas Roskies concludes that the science maybe developing our understanding of volition or "will," but it yet offers nothing for developing the "free" part of the

"free will" discussion.[19]

There is also the question of the influence of such interpretations in people's behaviour. In 2008, psychologistsKathleen Vohs and Jonathan Schooler published a study on how people behave when they are prompted to thinkthat determinism is true. They asked their subjects to read one of two passages: one suggesting that behaviour boilsdown to environmental or genetic factors not under personal control; the other neutral about what influencesbehaviour. The participants then did a few math problems on a computer. But just before the test started, they wereinformed that because of a glitch in the computer it occasionally displayed the answer by accident; if this happened,they were to click it away without looking. Those who had read the deterministic message were more likely tocheat on the test. "Perhaps, denying free will simply provides the ultimate excuse to behave as one likes," Vohs and

Schooler suggested.[20][21]

Notable Experiments

The Libet experiment

A pioneering experiment in this field was conducted by Benjamin Libet in the 1980s, in which he asked eachsubject to choose a random moment to flick their wrist while he measured the associated activity in their brain (inparticular, the build-up of electrical signal called the readiness potential). Although it was well known that thereadiness potential preceded the physical action, Libet asked how the readiness potential corresponded to the feltintention to move. To determine when the subjects felt the intention to move, he asked them to watch the second

hand of a clock and report its position when they felt that they had felt the conscious will to move.[22]

Libet found that the unconscious brain activity leading up to the conscious decision by the subject to flick his wrist

began approximately half a second before the subject consciously felt that he had decided to move.[22][23] Libet'sfindings suggest that decisions made by a subject are first being made on a subconscious level and only afterwardbeing translated into a "conscious decision", and that the subject's belief that it occurred at the behest of his will wasonly due to his retrospective perspective on the event.

scientists were telling people. Butscientists, especially in the last fewyears, have been on a rampage -writing ill-considered publicpronouncements about free willwhich... verge on socialirresponsibility. ”

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Libet's experiment: (0) repose, until (1) the

readiness potential is detected, (2-Libet's W) the

volunteer memorizes a dot position upon feeling

their intention, and (3) then acts.

Typical

recording of the

readiness

potential.

Benjamin Libet

investigated

whether this

neural activity

corresponded to

the "felt

intention" (or

will) to move of

experimental

subjects.

The interpretation of these findings has been criticized by Daniel Dennett, who argues that people will have to shifttheir attention from their intention to the clock, and that this introduces temporal mismatches between the felt

experience of will and the perceived position of the clock hand.[24][25] Consistent with this argument, subsequent

studies have shown that the exact numerical value varies depending on attention.[26][27] Despite the differences in

the exact numerical value, however, the main finding has held.[5][28][29] Philosopher Alfred Mele criticizes thisdesign for other reasons. Having attempted the experimenthimself, Mele explains that "the awareness of the intention tomove" is an ambiguous feeling at best. For this reason heremained skeptical of interpreting the subjects' reported

times for comparison with their 'readiness potential'.[30]

Criticisms

In a variation of this task, Haggardand Eimer asked subjects to decidenot only when to move their hands,but also to decide which hand tomove. In this case, the felt intention

correlated much more closely with the "lateralized readiness potential" (LRP), an ERPcomponent which measures the difference between left and right hemisphere brain activity.Haggard and Eimer argue that the feeling of conscious will must therefore follow the decision

of which hand to move, since the LRP reflects the decision to lift a particular hand.[26]

A more direct test of the relationship between the readiness potential and the "awareness ofthe intention to move" was conducted by Banks and Isham (2009). In their study,participants performed a variant of the Libet's paradigm in which a delayed tone followed thebutton press. Subsequently, research participants reported the time of their intention to act(e.g., Libet's "W"). If W were time-locked to the readiness potential, W would remainuninfluenced by any post-action information. However, findings from this study show that Win fact shifts systematically with the time of the tone presentation, implicating that W is, at leastin part, retrospectively reconstructed rather than pre-determined by the readiness

potential.[31]

A study conducted by Jeff Miller and Judy Trevena (2009) suggests that the readinesspotential (RP) signal in Libet's experiments doesn't represent a decision to move, but that it's

merely a sign that the brain is paying attention.[32] In this experiment the classical Libetexperiment was modified by playing an audio tone indicating to volunteers to decide whetherto tap a key or not. The researchers found that there was the same RP signal in both cases, regardless of whetheror not volunteers actually elected to tap, which suggests that the RP signal doesn't indicate that a decision has been

made.[33][34]

In a second experiment, researchers asked volunteers to decide on the spot whether to use left hand or right to tapthe key while monitoring their brain signals, and they found no correlation among the signals and the chosen hand.This criticism has itself been criticized by free-will researcher Patrick Haggard, who mentions literature that

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distinguishes two different circuits in the brain that lead to action: a "stimulus-response" circuit and a "voluntary"circuit. According to Haggard, researchers applying external stimuli may not be testing the proposed voluntary

circuit, nor Libet's hypothesis about internally triggered actions.[35]

Libet's interpretation of the ramping up of brain activity prior to the report of conscious "will" continues to drawheavy criticism. Studies have questioned participants' ability to report the timing of their "will". Authors have foundthat preSMA activity is modulated by attention (attention precedes the movement signal by 100ms), and the prior

activity reported could therefore have been product of paying attention to the movement.[36] They also found thatthe perceived onset of intention depends on neural activity that takes place after the execution of action.Transcranial magnetic stimulation (TMS) applied over the preSMA after a participant performed an action shiftedthe perceived onset of the motor intention backward in time, and the perceived time of action execution forward in

time.[37]

Others have speculated that the preceding neural activity reported by Libet may be an artefact of averaging the time

of "will", wherein neural activity does not always precede reported "will".[27] In a similar replication they alsoreported no difference in electrophysiological signs before a decision not to move, and before a decision to

move.[32]

Despite his findings, Libet himself did not interpret his experiment as evidence of the inefficacy of conscious free will— he points out that although the tendency to press a button may be building up for 500 milliseconds, the conscious

will retains a right to veto any action at the last moment.[38] According to this model, unconscious impulses toperform a volitional act are open to suppression by the conscious efforts of the subject (sometimes referred to as"free won't"). A comparison is made with a golfer, who may swing a club several times before striking the ball. Theaction simply gets a rubber stamp of approval at the last millisecond. Max Velmans argues however that "free

won't" may turn out to need as much neural preparation as "free will" (see below).[39]

Some studies have however replicated Libet's findings, whilst addressing some of the original criticisms.[40] Arecent study has found that individual neurons were found to fire 2 seconds before a reported "will" to act (long

before EEG activity predicted such a response).[13] Itzhak Fried replicated Libet's findings in 2011 at the scale ofthe single neuron. This was accomplished with the help of volunteer epilepsy patients, who needed electrodesimplanted deep in their brain for evaluation and treatment anyway. Now able to monitor awake and movingpatients, the researchers replicated the timing anomalies that were discovered by Libet and are discussed in the

following study.[13]

William R. Klemm pointed out the inconclusiveness of these tests due to design limitations and data interpretations

and proposed less ambiguous experiments.[41] Adrian G. Guggisberg and Annaïs Mottaz have also challenged

Itzhak Fried's findings.[42]

A study by Aaron Schurger and colleagues published in PNAS [43] challenged assumptions about the causal natureof the readiness potential itself (and the "pre-movement buildup" of neural activity in general), casting doubt on

conclusions drawn from studies such as Libet's [22] and Fried's.[13] See The Information Philosopher(http://www.informationphilosopher.com/solutions/scientists/schurger/) and New Scientist(http://www.newscientist.com/article/dn22144-brain-might-not-stand-in-the-way-of-free-will.html) for commentaryon this study.

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It is difficult to

identify exactly

when a person

becomes aware of

his action. Some

findings indicate

that awareness

comes after actions

have already begun

in the brain.

Unconscious actions

Timing intentions compared to actions

A study by Masao Matsuhashi and Mark Hallett, published in 2008, claims to have replicated Libet's findings

without relying on subjective report or clock memorization on the part of participants.[40] The authors believe thattheir method can identify the time (T) at which a subject becomes aware of his own movement. Matsuhashi andHallet argue that this time not only varies, but often occurs after early phases of movement genesis have alreadybegun (as measured by the readiness potential). They conclude that a person's awareness cannot be the cause ofmovement, and may instead only notice the movement.

The experiment

Matsuhashi and Hallett's study can be summarized thus. The researchers hypothesizedthat, if our conscious intentions are what causes movement genesis (i.e. the start of anaction), then naturally, our conscious intentions should always occur before any movementhas begun. Otherwise, if we ever become aware of a movement only after it has alreadybeen started, our awareness could not have been the cause of that particular movement.Simply put, conscious intention must precede action if it is its cause.

To test this hypothesis, Matsuhashi and Hallet had volunteers perform brisk fingermovements at random intervals, while not counting or planning when to make such (future)movements, but rather immediately making a movement as soon as they thought about it.An externally controlled "stop-signal" sound was played at pseudo random intervals, andthe volunteers had to cancel their intent to move if they heard a signal while being aware oftheir own immediate intention to move. Whenever there was an action (finger movement),the authors documented (and graphed) any tones that occurred before that action. Thegraph of tones before actions therefore only shows tones (a) before the subject is evenaware of his "movement genesis" (or else they would have stopped or "vetoed" themovement), and (b) after it is too late to veto the action. This second set of graphed tonesis of little importance here.

In this work, "movement genesis" is defined as the brain process of making movement, of which physiologicalobservations have been made (via electrodes) indicating that it may occur before conscious awareness of intent tomove (see Benjamin Libet).

By looking to see when tones started preventing actions, the researchers supposedly know the length of time (inseconds) that exists between when a subject holds a conscious intention to move and performs the action ofmovement. This moment of awareness (as seen in the graph below) is dubbed "T" (the mean time of consciousintention to move). It can be found by looking at the border between tones and no tones. This enables theresearchers to estimate the timing of the conscious intention to move without relying on the subject's knowledge ordemanding them to focus on a clock. The last step of the experiment is to compare time T for each subject withtheir Event-related potential (ERP) measures (e.g. seen in this page's lead image), which reveal when their fingermovement genesis first begins.

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A simple "signalling

noise" is used, but it is

to warn participants

that they must prevent

any actions they are

aware of.

The researchers found that the time of the conscious intention to move T normally occurred too late to be the causeof movement genesis. See the example of a subject's graph below on the right. Although it is not shown on thegraph, the subject's readiness potentials (ERP) tells us that his actions start at –2.8 seconds, and yet this issubstantially earlier than his conscious intention to move, time "T" (−1.8 seconds). Matsuhashi and Hallet concludedthat the feeling of the conscious intention to move does not cause movement genesis; both the feeling of intention

and the movement itself are the result of unconscious processing.[40]

Analysis and interpretation

This study is similar to Libet's in some ways: volunteers were again asked to performfinger extensions in short, self-paced intervals. In this version of the experiment,researchers introduced randomly timed "stop tones" during the self paced movements.If participants were not conscious of any intention to move, they simply ignored thetone. On the other hand, if they were aware of their intention to move at the time of thetone, they had to try to veto the action, then relax for a bit before continuing self-pacedmovements. This experimental design allowed Matsuhashi and Hallet to see when,once the subject moved his finger, any tones occurred. The goal was to identify theirown equivalent of Libet’s W, their own estimation of the timing of the consciousintention to move, which they would call "T".

Testing the hypothesis that 'conscious intention occurs after movement genesis hasalready begun' required the researchers to analyse the distribution of responses totones before actions. The idea is that, after time T, tones will lead to vetoing and thus areduced representation in the data. There would also be a point of no return P where atone was too close to the movement onset for the movement to be vetoed. In otherwords, the researchers were expecting to see the following on the graph: manyunsuppressed responses to tones while the subjects are not yet aware of their

movement genesis, followed by a drop in the number of unsuppressed responses to tones during a certain period oftime during which the subjects are conscious of their intentions and are stopping any movements, and finally a briefincrease again in unsuppressed responses to tones when the subjects do not have the time to process the tone andprevent an action - they have passed the action's "point of no return". That is exactly what the researchers found(see the graph on the right, below).

The graph shows the times at which unsuppressed responses to tones occurred when the volunteer moved. Heshowed many unsuppressed responses to tones (dubbed "tone events" on the graph) on average up until 1.8seconds before movement onset, but a significant decrease in tone events immediately after that time. Presumablythis is because the subject usually became aware of his intention to move at about −1.8 seconds, which is thenlabelled point T. Since most actions are vetoed if a tone occurs after point T, there are very few tone eventsrepresented during that range. Finally, there is a sudden increase in the number of tone events at 0.1 seconds,meaning this subject has passed point P. Matsuhashi and Hallet were thus able to establish an average time T (−1.8seconds) without subjective report. This, they compared to ERP measurements of movement, which had detectedmovement beginning at about −2.8 seconds on average for this participant. Since T — like Libet’s original W —was often found after movement genesis had already begun, the authors concluded that the generation of awarenessoccurred afterwards or in parallel to action, but most importantly, that it was probably not the cause of the

movement.[40]

Criticisms

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Graphing tones as they appeared (or didn't) in the

time before any action. In this case, researchers

believe the subject becomes aware of his actions at

about -1.769 seconds (this is time 'T'). A typical

subject's ERP recordings suggest movement

preparation as early as −2.8 seconds.

As green light switches

to yellow, research

seems to suggest that

humans cannot tell the

difference between

"deciding" to keep

driving, and having no

time to decide at all.

Haggard describes other studies at the neuronal levels asproviding "a reassuring confirmation of previous studies that

recorded neural populations"[6] such as the one justdescribed. Note that these results were gathered usingfinger movements, and may not necessarily generalize toother actions such as thinking, or even other motor actionsin different situations. Indeed, the human act of planning hasimplications for free will and so this ability must also beexplained by any theories of unconscious decision making.Philosopher Alfred Mele also doubts the conclusions ofthese studies. He explains that simply because a movementmay have been initiated before our "conscious self" hasbecome aware of it does not mean our consciousness doesnot still get to approve, modify, and perhaps cancel (called

vetoing) the action.[44]

Unconsciously cancelling actions

The possibility that human "free won't" is also theprerogative of the subconscious is being explored.

Retrospective judgement of free choice

Recent research by Simone Kühn and Marcel Brass suggests that our consciousnessmay not be what causes some actions to be vetoed at the last moment. First of all,their experiment relies on the simple idea that we ought to know when we consciouslycancel an action (i.e. we should have access to that information ). Secondly, theysuggest that access to this information means humans should find it easy to tell, justafter completing an action, whether it was impulsive (there being no time to decide)and when there was time to deliberate (the participant decided to allow/not to veto theaction). The study found evidence that subjects could not tell this important difference.This again leaves some conceptions of free will vulnerable to the introspection illusion.The researchers interpret their results to mean that the decision to "veto" an action isdetermined subconsciously, just as the initiation of the action may have been

subconscious in the first place.[45]

The experiment

The experiment involved asking volunteers to respond to a go-signal by pressing an

electronic "go" button as quickly as possible.[45] In this experiment the go-signal wasrepresented as a visual stimulus shown on a monitor (e.g. a green light as shown on thepicture). The participants' reaction times (RT) were gathered at this stage, in what wasdescribed as the "primary response trials".

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The primary response trials were then modified, in which 25% of the go-signals were subsequently followed by anadditional signal – either a "stop" or "decide" signal. The additional signals occurred after a "signal delay" (SD), arandom amount of time up to 2 seconds after the initial go-signal. They also occurred equally, each representing12.5% of experimental cases. These additional signals were represented by the initial stimulus changing colour (e.g.to either a red or orange light). The other 75% of go-signals were not followed by an additional signal – and wastherefore considered the "default" mode of the experiment. The participants' task of responding as quickly aspossible to the initial signal (i.e. pressing the "go" button) remained.

Upon seeing the initial go-signal, the participant would immediately intend on pressing the "go" button. Theparticipant was instructed to cancel their immediate intention to press the "go" button if they saw a stop signal. Theparticipant was instructed to select randomly (at their leisure) between either pressing the "go" button, or notpressing it, if they saw a decide signal. Those trials in which the decide signal was shown after the initial go-signal("decide trials"), for example, required that the participants prevent themselves from acting impulsively on the initialgo-signal and then decide what to do. Due to the varying delays, this was sometimes impossible (e.g. some decidesignals simply appeared too late in the process of them both intending to and pressing the go button for them to beobeyed).

Those trials in which the subject reacted to the go-signal impulsively without seeing a subsequent signal show aquick RT of about 600 ms. Those trials in which the decide signal was shown too late, and the participant hadalready enacted their impulse to press the go-button (i.e. had not decided to do so), also show a quick RT of about600 ms. Those trials in which a stop signal was shown and the participant successfully responded to it, do not showa response time. Those trials in which a decide signal was shown, and the participant decided not to press the go-button, also do not show a response time. Those trials in which a decide signal was shown, and the participant hadnot already enacted their impulse to press the go-button, but (in which it was theorised that they) had had the

opportunity to decide what to do, show a comparatively slow RT, in this case closer to 1400 ms.[45]

The participant was asked at the end of those "decide trials" in which they had actually pressed the go-buttonwhether they had acted impulsively (without enough time to register the decide signal before enacting their intent topress the go-button in response to the initial go-signal stimulus), or had acted based upon a conscious decisionmade after seeing the decide signal. Based upon the response time data however, it appears there was discrepancybetween when the user thought they had had the opportunity to decide (and had therefore not acted on theirimpulses) - in this case deciding to press the go-button, and when they thought they had acted impulsively (basedupon the initial go-signal) - where the decide signal came too late to be obeyed.

The rationale

Kuhn and Brass wanted to test participant self-knowledge. The first step was that after every decide trial,participants were next asked whether they had actually had time to decide. Specifically, the volunteers were askedto label each decide trial as either failed-to-decide (the action was the result of acting impulsively on the initial go-signal) or successful decide (the result of a deliberated decision). See the diagram on the right for this decide trialsplit: failed-to-decide and successful decide; the next split in this diagram (participant correct or incorrect) will beexplained at the end of this experiment. Note also that the researchers sorted the participants’ successful decidetrials into "decide go" and "decide nogo", but were not concerned with the nogo trials since they did not yield anyRT data (and are not featured anywhere in the diagram on the right). Note that successful stop trials did not yieldRT data either.

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The different types of trials and their different possible outcomes.

The general distribution of reaction times for the

different trials. Notice the timing of the two peaks

for trials labelled "successful decide".

Kuhn and Brass now knew what to expect: primary response trials, any failed stop trials, and the "failed-to-decide"trials were all instances where the participant obviously acted impulsively – they would show the same quick RT. Incontrast, the "successful decide" trials(where the decision was a "go" and thesubject moved) should show a slower RT.Presumably, if deciding whether to veto isa conscious process, volunteers shouldhave no trouble distinguishing impulsivityfrom instances of true deliberatecontinuation of a movement. Again, this isimportant since decide trials require thatparticipants rely on self-knowledge. Notethat stop trials cannot test self-knowledgebecause if the subject does act, it is

obvious to them that they reacted impulsively.[45]

Results and implications

Unsurprisingly, the recorded RTs for the primary responsetrials, failed stop trials, and "failed-to-decide" trials allshowed similar RTs: 600 ms seems to indicate an impulsiveaction made without time to truly deliberate. What the tworesearchers found next was not as easy to explain: whilesome "successful decide" trials did show the tell-tale slowRT of deliberation (averaging around 1400 ms), participantshad also labelled many impulsive actions as "successfuldecide". This result is startling because participants shouldhave had no trouble identifying which actions were theresults of a conscious "I will not veto", and which actionswere un-deliberated, impulsive reactions to the initial go-signal. As the authors explain:

“ [The results of the experiment] clearly

argue against Libet’s assumption that a

veto process can be consciously initiated.

He used the veto in order to reintroduce

the possibility to control the unconsciously

initiated actions. But since the subjects are

not very accurate in observing when they

have [acted impulsively instead ofdeliberately], the act of vetoing cannot be

consciously initiated.[45] ”In decide trials the participants, it seems, were not able to reliably identify whether they had really had time todecide – at least, not based on internal signals. The authors explain that this result is difficult to reconcile with the

idea of a conscious veto, but simple to understand if the veto is considered an unconscious process.[45] Thus it

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seems that the intention to move might not only arise from the subconscious, but it may only be inhibited if thesubconscious says so. This conclusion could suggest that the phenomenon of "consciousness" is more of narrationthan direct arbitration (i.e. unconscious processing causes all thoughts, and these thoughts are again processedsubconsciously).

Criticisms

After the above experiments, the authors concluded that subjects sometimes could not distinguish between"producing an action without stopping and stopping an action before voluntarily resuming", or in other words, they

could not distinguish between actions that are immediate and impulsive as opposed to delayed by deliberation.[45]

To be clear, one assumption of the authors is that all the early (600 ms) actions are unconscious, and all the lateractions are conscious. These conclusions and assumptions have yet to be debated within the scientific literature oreven replicated (it is a very early study).

The results of the trial in which the so-called "successful decide" data (with its respective longer time measured) wasobserved may have possible implications for our understanding of the role of consciousness as the modulator of agiven action or response — and these possible implications cannot merely be omitted or ignored without validreasons, specially when the authors of the experiment suggest that the late decide trials were actually

deliberated.[45]

It is worth noting that Libet consistently referred to a veto of an action that was initiated endogenously.[38] That is, aveto that occurs in the absence of external cues, instead relying on only internal cues (if any at all). This veto may bea different type of veto than the one explored by Kühn and Brass using their decide signal.

Daniel Dennett also argues that no clear conclusion about volition can be derived from Benjamin Libet'sexperiments supposedly demonstrating the non-existence of conscious volition. According to Dennett, ambiguities inthe timings of the different events involved. Libet tells when the readiness potential occurs objectively, usingelectrodes, but relies on the subject reporting the position of the hand of a clock to determine when the consciousdecision was made. As Dennett points out, this is only a report of where it seems to the subject that various thingscome together, not of the objective time at which they actually occur.

Suppose Libet knows that your readiness potential peaked at millisecond 6,810 of the experimentaltrial, and the clock dot was straight down (which is what you reported you saw) at millisecond 7,005.How many milliseconds should he have to add to this number to get the time you were conscious of it?The light gets from your clock face to your eyeball almost instantaneously, but the path of the signalsfrom retina through lateral geniculate nucleus to striate cortex takes 5 to 10 milliseconds — a paltryfraction of the 300 milliseconds offset, but how much longer does it take them to get to you. (Or areyou located in the striate cortex?) The visual signals have to be processed before they arrive atwherever they need to arrive for you to make a conscious decision of simultaneity. Libet's methodpresupposes, in short, that we can locate the intersection of two trajectories:

the rising-to-consciousness of signals representing the decision to flick

the rising to consciousness of signals representing successive clock-face orientations

so that these events occur side-by-side as it were in place where their simultaneity can be

noted.[46][47]

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Neuronal prediction of free will

Despite criticisms, experimenters are still trying to gather data that may support the case that conscious "will" can bepredicted from brain activity. fMRI machine learning of brain activity (multivariate pattern analysis) has been used to

predict the user choice of a button (left/right) up to 7 seconds before their reported will of having done so.[5] Brainregions successfully trained for prediction included the frontopolar cortex (anterior medial prefrontal cortex) andprecuneus/posterior cingulate cortex (medial parietal cortex). In order to ensure report timing of conscious "will" toact, they showed the participant a series of frames with single letters (500ms apart), and upon pressing the chosenbutton (left or right) they were required to indicate which letter they had seen at the moment of decision. This studyreported a statistically significant 60% accuracy rate, which may be limited by experimental setup; machine learningdata limitations (time spent in fMRI) and instrument precision.

Another version of the fMRI multivariate pattern analysis experiment was conducted using an abstract decisionproblem, in an attempt to rule out the possibility of the prediction capabilities being product of capturing a built-up

motor urge.[48] Each frame contained a central letter like before, but also a central number, and a surrounding 4possible "answers numbers". The participant first chose in their mind whether they wished to perform an addition ordifference operation (and noted the central letter on the screen at the time of this decision). The participant thenperformed the mathematical operation based on the central numbers shown in the next two frames. In the followingframe the participant then chose the "answer number" corresponding to the result of the operation. They werefurther presented with a frame which allowed them to indicate the central letter appearing on the screen at the timeof their original decision. This version of the experiment discovered a brain prediction capacity of up to 5 secondsbefore the conscious will to act.

Multivariate pattern analysis using EEG has suggested that an evidence based perceptual decision model may be

applicable to free will decisions.[49] It was found that decisions could be predicted by neural activity immediatelyafter stimulus perception. Furthermore, when the participant was unable to determine the nature of the stimulus therecent decision history predicted the neural activity (decision). The starting point of evidence accumulation was ineffect shifted towards a previous choice (suggesting a priming bias). Another study has found that subliminallypriming a participant for a particular decision outcome (showing a cue for 13ms) could be used to influence free

decision outcomes.[50] Likewise, it has been found that decision history alone can be used to predict futuredecisions. The prediction capacities of the Soon et al. (2008) experiment were successfully replicated using a linear

SVM model based on participant decision history alone (without any brain activity data).[51] Despite this, a recent

study has sought to confirm the applicability of a perceptual decision model to free will decisions.[52] When shown amasked and therefore invisible stimulus, participants were asked to either guess between a category or make a freedecision for a particular category. Multivariate pattern analysis using fMRI could be trained on "free decision" datato successfully predict "guess decisions", and trained on "guess data" in order to predict "free decisions" (in theprecuneus and cuneus region).

Contemporary voluntary decision prediction tasks have been criticised based on the possibility the neuronalsignatures for pre-conscious decisions could actually correspond to lower conscious processing rather than

unconscious processing.[53] People may be aware of their decisions before making their report yet need to waitseveral seconds to be certain. Such a model does not however explain what is left unconscious if everything can beconscious at some level (and the purpose of defining separate systems). Yet limitations remain in free will predictionresearch to date. In particular, the prediction of considered judgements from brain activity involving thoughtprocesses beginning minutes rather than seconds before a conscious will to act, including the rejection of aconflicting desire. Such are generally seen to be the product of sequences of evidence accumulating judgements.

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Transcranial magnetic stimulation

uses magnetism to safely stimulate

or inhibit parts of the brain.

Scientists were able

to change which

hand subjects

normally chose to

move without

subjects noticing the

influence.

Other related phenomena

Retrospective construction

It has been suggested that sense authorship is an illusion.[54] Unconscious causes of thought and action mightfacilitate thought and action, while the agent experiences the thoughts and actions as being dependent on consciouswill. We may over-assign agency because of the evolutionary advantage that once came with always suspectingthere might be an agent doing something (e.g. predator). The idea behind retrospective construction is that, whilepart of the "yes, I did it" feeling of agency seems to occur during action, there also seems to be processingperformed after the fact - after the action is performed - to establish the full feeling of agency.

Unconscious agency processing can even alter, in the moment, how we perceive the timing of sensations or

actions.[35][37] Kühn and Brass apply retrospective construction to explain the two peaks in "successful decide"RT's. They suggest that the late decide trials were actually deliberated, but that the impulsive early decide trials thatshould have been labelled "failed to decide" were mistaken during unconscious agency processing. They say thatpeople "persist in believing that they have access to their own cognitive processes" when in fact we do a great dealof automatic unconscious processing before conscious perception occurs.

Manipulating choice

Some research suggests that TMS can be used to manipulate the perception

of authorship of a specific choice.[55] Experiments showed thatneurostimulation could affect which hands people move, even though theexperience of free will was intact. An early TMS study revealed thatactivation of one side of the neocortex could be used bias the selection of

one's opposite side hand in a forced choice decision task.[56] Ammon andGandevia found that it was possible to influence which hand people move bystimulating frontal regions that are involved in movement planning usingtranscranial magnetic stimulation in the left or right hemisphere of the brain.

Right-handed people would normally choose tomove their right hand 60% of the time, but whenthe right hemisphere was stimulated they wouldinstead choose their left hand 80% of the time(recall that the right hemisphere of the brain isresponsible for the left side of the body, and the left hemisphere for the right). Despite theexternal influence on their decision-making, the subjects continued to report that theybelieved their choice of hand had been made freely. In a follow-up experiment, AlvaroPascual-Leone and colleagues found similar results, but also noted that the transcranialmagnetic stimulation must occur within 200 milliseconds, consistent with the time-course

derived from the Libet experiments.[57]

However, further attempts to replicate such results have failed[58] and later Jeffrey Graystates in his book Consciousness: Creeping up on the Hard Problem, that tests looking

for the influence of electromagnetic fields on brain function have been universally negative in their result.[59]

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Manipulating the perceived intention to move

Various studies indicate that the perceived intention to move (have moved) can be manipulated. Studies havefocused on the pre-supplementary motor area (pre-SMA) of the brain, in which readiness potential indicating thebeginning of a movement genesis has been recorded by EEG. In one study, directly stimulating the pre-SMAcaused volunteers to report a feeling of intention, and sufficient stimulation of that same area caused physical

movement.[35] In a similar study, it was found that people with no visual awareness of their body can have their

limbs be made to move without having any awareness of this movement, by stimulating premotor brain regions.[60]

When their parietal cortices were stimulated, they reported an urge (intention) to move a specific limb (that theywanted to do so). Furthermore, stronger stimulation of the parietal cortex resulted in the illusion of having movedwithout having done so.

This suggests that awareness of an intention to move may literally be the "sensation" of the body’s early movement,but certainly not the cause. Other studies have at least suggested that "The greater activation of the SMA, SACC,and parietal areas during and after execution of internally generated actions suggests that an important feature ofinternal decisions is specific neural processing taking place during and after the corresponding action. Therefore,awareness of intention timing seems to be fully established only after execution of the corresponding action, in

agreement with the time course of neural activity observed here."[61]

Another experiment involved an electronic ouija board where the device's movements were manipulated by the

experimenter, while the participant was led to believe they were entirely self-conducted.[62] The experimenterstopped the device on occasions and asked the participant how much they themselves felt like they wanted to stop.The participant also listened to words in headphones; and it was found that if experimenter stopped next to anobject that came through the headphones they were more likely to say they wanted to stop there. If the participantperceived having the thought at the time of the action, then it was assigned as intentional. It was concluded that astrong illusion of perception of causality requires; priority (we assume the thought must precede the action),consistency (the thought is about the action), and exclusivity (no other apparent causes or alternative hypotheses).

Lau et al. set up an experiment where subjects would look at an analogue-style clock, and a red dot would movearound the screen. Subjects were told to click the mouse button whenever they felt the intention to do so. Onegroup was given a transcranial magnetic stimulation (TMS) pulse, and the other was given a sham TMS. Subjects inthe intention condition were told to move the cursor to where it was when they felt the inclination to press thebutton. In the movement condition, subjects moved their cursor to where it was when they physically pressed thebutton. Results showed the TMS was able to shift the perceived intention forward by 16 ms, and shifted back the14 ms for the movement condition. Perceived intention could be manipulated up to 200 ms after the execution ofthe spontaneous action, indicating that the perception of intention occurred after the executive motor

movements.[37] Often it is thought that free will were to exist, it would require intention to be the causal source ofbehavior. These results show that intention may not be the causal source of all behavior.

Related models

The idea that intention co-occurs with (rather than causes) movement is reminiscent of "forward models of motorcontrol" (or FMMC, which have been used to try to explain inner speech). FMMCs describe parallel circuits:movement is processed in parallel with other predictions of movement; if the movement matches the prediction - thefeeling of agency occurs. FMMCs have been applied in other related experiments. Metcalfe and her colleagues

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Neurological disorders such as

alien hand syndrome make a

person lose his sense of agency.

used an FMMC to explain how volunteers determine whether they are in control of a computer game task. On theother hand, they acknowledge other factors too. The authors attribute feelings of agency to desirability of the results

(see self serving biases) and top-down processing (reasoning and inferences about the situation).[63]

In this case, it is by the application of the forward model that one might imagine how other consciousness processescould be the result of efferent, predictive processing. If the conscious self isthe efferent copy of actions and vetoes being performed, then theconsciousness is a sort of narrator of what is already occurring in the body,and an incomplete narrator at that. Haggard, summarizing data taken fromrecent neuron recordings, says "these data give the impression that consciousintention is just a subjective corollary of an action being about to

occur".[6][13] Parallel processing helps explain how we might experience asort of contra-causal free will even if it were determined.

How the brain constructs consciousness is still a mystery, and cracking itopen would have a significant bearing on the question of free will. Numerousdifferent models have been proposed, for example, the Multiple DraftsModel which argues that there is no central Cartesian theater whereconscious experience would be represented, but rather that consciousness is located all across the brain. Thismodel would explain the delay between the decision and conscious realization, as experiencing everything as acontinuous 'filmstrip' comes behind the actual conscious decision. In contrast, there exist models of Cartesianmaterialism that have gained recognition by neuroscience, implying that there might be special brain areas that storethe contents of consciousness; this does not, however, rule out the possibility of a conscious will. Other modelssuch as epiphenomenalism argue that conscious will is an illusion, and that consciousness is a by-product of physicalstates of the world. Work in this sector is still highly speculative, and researchers favor no single model ofconsciousness. (See also: Philosophy of mind.)

Although humans clearly make choices, the role of consciousness (at least, when it comes to motor movements)may need re-conceptualization. Only one thing is certain: the correlation of a conscious "intention to move" with asubsequent "action" does not guarantee causation. Recent studies cast doubt on such a causal relation, and somore empirical data is required.

Related brain disorders

Various brain disorders implicate the role of unconscious brain processes in decision making tasks. Auditory

hallucinations produced by Schizophrenia seem to suggest a divergence of will and behaviour.[54] The left brain ofpeople whose hemispheres have been disconnected has been observed to invent explanations for body movementinitiated by the opposing (right) hemisphere, perhaps based on the assumption that their actions are consciously

willed.[64] Likewise, people with 'alien hand syndrome' are known to conduct complex motor movements against

their will.[65]

Neural models of voluntary action

A neural model for voluntary action proposed by Haggard comprises two major circuits.[35] The first involving earlypreparatory signals (basal ganglia substantia nigra and striatum), prior intention and deliberation (medial prefrontalcortex), motor preparation/readiness potential (preSMA and SMA), and motor execution (primary motor cortex,

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spinal cord and muscles). The second involving the parietal-pre-motor circuit for object-guided actions, forexample grasping (premotor cortex, primary motor cortex, primary somatosensory cortex, parietal cortex, andback to the premotor cortex). He proposed that voluntary action involves external environment input ('whendecision'), motivations/reasons for actions (early 'whether decision'), task and action selection ('what decision'), afinal predictive check (late 'whether decision') and action execution.

Another neural model for voluntary action also involves what, when, and whether (WWW) based decisions.[66]

The 'what' component of decisions is considered a function of the anterior cingulate cortex, which is involved in

conflict monitoring.[67] The timing ('when') of the decisions are considered a function of the preSMA and SMA,

which is involved in motor preparation.[68] Finally, the 'whether' component is considered a function of the dorsal

medial prefrontal cortex.[66]

Prospection

Martin Seligman and others criticize the classical approach in science which views animals and humans as "drivenby the past", and suggest instead that people and animals draw on experience to evaluate prospects they face, andact accordingly. The claim is made that this purposive action includes evaluation of possibilities that have never

occurred before, and is experimentally verifiable.[69][70]

Seligman and others argue that free will and the role of subjectivity in consciousness can be better understood bytaking such a "prospective" stance on cognition, and that "accumulating evidence in a wide range of research

suggests [this] shift in framework".[70]

See also

Thought identification, through the use of technologyUnconscious mind

Adaptive unconsciousNeural decoding

Sam HarrisDick Swaab

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External links

Fate, Freedom and Neuroscience (http://iai.tv/video/fate-freedom-and-neuroscience) - a debate on whetherneuroscience has proved that free will is an illusion by the Institute of Art and Ideas featuring Oxfordneuroscientist Nayef Al-Rodhan, East End psychiatrist and broadcaster Mark Salter, and LSE philosopher

Kristina Musholt debate the limits of science.

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