neuroscienze e libero arbitrio

Giuseppe SartoriUniversità di Padova

Neuroscienze e Libero Arbitrio

Free will and science

Free will Intentions

Decision-makingAgencyExecutive controlInternally vs. externally generated actions

Philosophy

Theology

Genetics

Brain or mind sciencesPhysics

Free will and conscious intentions

Conscious or purposeful plan for a future action, that exists prior to and

independently of action execution

Subjectively, is the proximal cause of movement (also called motor intention)

Intention is crucial for the experience of free will. Searle (1983) distinguishes two types of intentions:

The Libet task

Used to measure when a person

forms the motor intention to

execute an action

From Haggard, 2008, Nat Rev Neuro

Intention reported ~200 ms before

movement onset (will judgment, W)

RP starts up to 2 s before movement

Inferential processes in conscious intentions

Theoretical background


“Reconstruction hypothesis” of intention (e.g. Dennett & Kinsbourne, 1992; Wegner, 2002)– Based on inference– Intention is retrospectively built as the cause of the movement

Empirical evidence– Action consequences affect intention attribution (Kuhn & Brass, 2009)– TMS after movement shifts the W-judgment (Lau et al., 2007)– W-judgment is inferred from apparent time of response, rather than actual

movement (Banks & Isham, 2009)

-

+

Movement onset

0-2 sVolta

ge (µ

V)

Most studies focus on pre-movement brain processes (e.g. Libet et al., 1983; Haggard & Eimer, 1999; Soon et al., 2008) ?



Post-action events modulate the experience of

intention

Reported time of intention is based not only on pre-action processes (i.e.

motor preparation)

W-judgment related to the apparent time of response

Role of action monitoring processes

Action-effect negativity (Nae) (Band et al., 2009). Reflects the linkage

between action and action-effects

Associated with changes in the W-judgments


Delayed auditory feedback signaling a response later than the actual one was delivered (5, 20, 40, or 60 ms)

16 participants (7 females, 19-24 years) performed a variant of the Libet task (Banks & Isham, 2009)

EEG activity was recorded (64 channels, ref mast)

Responding hand not

visible

Methods and procedure


W-judgment varied as a function of feedback delays

Results

Nae amplitude was larger for later feedbacks and

associated with shifts in the W-

judgment

• Reported time of intention (W-judgment) is partially based on inferential processes (i.e. external feedback signaling response)

• Action monitoring is involved in the experience of intention (Nae may reflect action-effect binding)

• However, results cast doubts on the Libet procedure as measure of conscious intentions– Can we exclude that participants respond as that the

intention “must have taken place” sometime before the external feedback?


Conclusions

Free will and science: a novel approach

Free will

Theology

Philosophy

Physics

Genetics

IntentionsDecision-makingAgencyExecutive controlInternally vs. externally generated actions

Brain or mind sciences

Free will and science: a novel approach

Free will

Theology

Philosophy

Physics

Genetics

Brain or mind sciences

Behaviour

Free will beliefs and motor preparation



The experience of free will is tightly connected with the idea of control

(e.g. choices)

Human societies are ruled on the idea that we have free will (e.g. personal

responsibility, punishment, reward)




Neuroscientific findings challenge the nature of free will

What would happen if people are induced to disbelieve in

free will?


• Social psychology demonstrates that it has important behavioural consequences• Increases cheating (Vohs & Schooler, 2008)• Reduces altruistic behaviour and promotes

antisocial tendencies (Baumeister et al., 2009)


Deterministic perspective (i.e. free will

is an illusion)

Ego depletionLess intentional effort

into behaviourLess responsibility for

own actions

Hypotheses


-

+

Movement onset

0-2 sVolta

ge (µ

V)

Readiness Potential (RP)Slow negative wave preceding voluntary movements

Modulated by level of intentionality and mental effort.

Absent or greatly reduced in automatic movements

Does disbelieving in free will alter

neurophysiological processes of motor

preparation?

Free will manipulation (deterministic worldview)

Ego depletion

(1) Disbelief in free will

(2) Reduced RP (EEG activity reflecting voluntary motor preparation)

(3) Effect already in the earlier stages of motor preparation

Hypotheses


Three hypotheses

• Free will belief manipulation – Participants read one of 2 texts taken from Crick’s book The

Astonishing Hypothesis and were asked to read it carefully (10’) for a comprehension test

no-free will group (n=14) control group (n=15)General concepts on consciousness. Free will was not mentioned

Key concepts conveyed by the text:“[…] Free will is an illusion […] Although we feel like we are free, our choices are pre-determined and we cannot change them […] We are nothing else than a pack of neurons“

Material and methods


2 groups


Auditory feedback signaling key press was delivered simultaneously or later than the actual response (20, 40, or 60

ms)

EEG activity was recorded (32 channels)


Free Will and Determinism scale (22 items, Likert 1-5)

In addition, Self-Control (Tangney Self-Control scale) and Social Desirability (Marlow-Crowne Social Desirability scale) were measured

Personal free will (8 items)

e.g. “I have free will even when my choices are limited by external circumstances”

General free will (14 items)

e.g. ”Life’s experiences cannot eliminate a person’s free will”



No-free will group reported weaker free will beliefs (personal FW scale) [t(27)=-2.86, p<.01]

Free will manpilation was effective in reducing free will belief in the no-free will group

Results


Reduced RP amplitude in the no-free will group [F(1,28) = 4.43, p < .05, ηp

2 = .136]

Main effect in frontal-central regions (max FCz)

Results


W-judgment did not differ between the 2

groups

Significant effect already at-1300 ms (i.e. early stages of motor preparation)

controlsno-free will

Results


Significant correlation between RP and scores on the personal FWD scale

• Basic motor preparation processes are influenced by whether people believe in free will

• The effect is clear before people become aware of the intention: pre-conscious level

• The manipulation does not affect intention at a conscious level (i.e. no differences in the W-judgments)

Conclusions


Conclusions


Dismissing free will belief

Less intentional effort and reduced sense of agency

Reduced feeling of responsibility

Careless and irresponsible behaviour

Speculative interpretation

Low self-efficacy/control beliefNegative emotions?

• Experience of intention is not only based on pre-action processes– Action-effect binding does not involve only motor

preparation, but also action monitoring

• Whether or not free will is an illusion, it is much better to believe in it!– Effects on very basic brain processes

General conclusions

• Reato d’impeto• Reazione a corto circuito

• Le intenzioni distali non sono soggette a questi effetti (premedidazione-deliberazione distale)

Psichiatria Forense

Imputabilità

• Capacità di intendere e di volere– Nesso di causa fra stato mentale patologico e

reato

• Infermità di mente– Alterazione patologica

• Come si documenta?– Approccio tassononimico - convenzionalista

Infermità di mente

PRESENZAASSENZA

CONFINE

SchizofreniaDisturbo di personalità

Alterazioni cerebraliVBM, DTI,ERP, fMRI

Alterazioni geneticheGenetica molecolare

Assenza di correlati neurali e genetici

Infermità di mente

Imaging – VBM + DTI

1.Il ricordo autobiografico

2.L’intenzione nell’azione criminosa

3.Ambiti di applicazione peritali: - Idoneità a rendere testimonianza- Vizio di mente

Due problemi centrali nel processo penale

• Autobiographical memory: personal experiences, specific, long-lasting and (usually) of significance to the self-system

• Most studies on autobiographical memory investigate how easy the information is retrieved (e.g., Crovitz & Schiffman, 1974; Kopelman, 1989).

• No studies have been conducted in order to evaluate the truthfulness of an autobiographical event.

Autobiographical memory: methods

• Autobiographical IAT•Computerizzato•Richiede due memorie autobiografiche alternative

(es. porta aperta vs porta chiusa)•Accuratezza diagnostica circa 92%•Criteri DAUBERT

Caratteristcihe dello IAT per memory-detection

The Autobiographical-IAT

The aIAT has been validated in a series of experiments:

• Card aIAT

• Mock Crime aIAT

• Holiday aIAT

• Suspension of driving license aIAT

TRUE FALSE“I'm in front of a computer” “I'm in front of a television”

CARD 4 CARD 7

“I chose card 4” “I chose card 7”


CARD 7 CARD 4

“I saw the card 7” “I saw the card 4”

Congruent Block for Card 4 choosers

Incongruent Block for card 7 choosers

Incongruent Block for Card 4 choosers

Congruent Block for card 7 choosers

Card IAT

Card experiment

Mock Crime experiment

Driving license experiment

700900

1100130015001700

Card selected "4 of diamonds"

Card selected "7 of clubs"

Reac

tion

Tim

e (m

s)

TRUE/Card 4 TRUE/Card 7

800

1000

1200

1400

1600

1800

2000

Guilty suspects Innocent suspectsR

eac

tio

n T

ime

(m

sec)

TRUE/I stole the CD-rom

TRUE/I did not steal the CD-rom

12001400160018002000220024002600

Drivers with suspended license

Control group

Re

acti

on

Tim

e (

mse

c)

TRUE/My driving license was suspended

TRUE/My driving license was not suspended

•Facilitating effect due to pairing of associated concepts

Card IAT: results

Accuratezza IATRelazione fra il valore del D-IAT e accuratezza diagnosticaDati di 5 esperimenti per un totale di 320 soggetti

Caratteristiche IAT per memory detection

1. Probabilità di diagnosi corretta2. Accuratezza media= 92%

• Holiday aIAT• 2 Card aIAT• 10 Card aIAT

non-faking group: standard IAT instructions;

naïve-faking group: beat the memory detector, and to

hide their true autobiographical memory to the

experimenter;

instructed-faking group: “slow down” on the congruent

block and “speed up” in the incongruent block (Fiedler &

Bluemke, 2005).

Non-faking group Naïve-faking group Instructed-faking group

500

700

900

1100

1300

1500

1700

1900

21002 Card experiment Congruent

Incongruent

Mea

n R

Ts

(mse

c)

Non-faking group Naive-faking group Instructed faking group

500

700

900

1100

1300

1500

1700

1900

2100

10 Cards experiment Congruent

Incongruent

me

an

RT

s (a

vera

ge

)

Non-faking group Naive-faking group Instructed-faking group

500

700

900

1100

1300

1500

1700

1900

2100

Holiday experiment Congruent

Incongruent

Me

an

RT

s (

ms

ec

)

Results:

Naïve fakers cannot fake the aIAT

Instructed fakers are faster in the Incongruent block than the Congruent block.

Detecting fakers

•AUC: 0.88

Conclusion: it is possible to identify subjects that tried to fake the aIAT from non fakers.

•Difference between single blocks (1, 2, and 4) and double blocks (3, 5) is larger in fakers than in non-fakers

Algorithm for detecting fakers

Method ResultsTRUE FALSE“I'm in front of a computer “I'm in front of a television”

True Intention False Intention“I will sleep in Padua” “I will sleep in Milan”


False Intention True Intention“I will sleep in Milan” “I will sleep in Padua”

It is possible to identify the participants’ real intentions

Intention detectionJournal of Cognitive Neuroscience 2011

Collocazione temporale dell’evento

Programmato

Casuale

Detecting prior intentions

Esempio di incontro intenzionale

• Soggetto 6: incontro intenzionale con Franco per ritrovarsi dopo tanto tempo.

• Frasi a-IAT

Incontro intenzionale:• Ho telefonato a Franco per vederci• Ho organizzato un incontro con Franco• Volevo riprendere i contatti con Franco• Volevo incontrare Franco da tempo• Ho fissato l’incontro a casa sua

Incontro casuale:1. Ho incontrato casualmente Franco2. Ho incrociato Franco facendo la spesa3. Senza volerlo ho incontrato Franco4. Per caso mi sono imbattuto in Franco5. Ho inaspettatamente visto Franco


Esempio di incontro casuale• Soggetto 1: incontro casuale con Patrizia al supermercato.

Incontro casuale:• Ho incrociato per caso Patrizia• Al supermercato ho visto per caso Patrizia• Venerdì all’improvviso ho trovato Patrizia• Inaspettatamente ho incontrato Patrizia• Mi si è avvicinata casualmente Patrizia

Incontro intenzionale:1. Volevo vedere Patrizia2. Ho inviato un sms a Patrizia3. Ho chiesto a Patrizia di incontrarci4. Ho fissato un appuntamento con Patrizia5. Alle 18 dovevo vedere Patrizia


INCONTRO INTENZIONALE

CONGRUENT= VERO/INTENZIONALE

INCONGRUENT= VERO/CASUALE

Incontro intenzionale

Numero soggetti con incontro intenzionale classificati correttamente: 12/12(1/12 appena sopra soglia)

Incontro intenzionale

INCONTRO CASUALE

CONGRUENT= VERO/INTENZIONALE

INCONGRUENT= VERO/CASUALE

congruent incongruent

Incontro casuale

Problematiche forensiE’ lamentata molto di frequenteSe provata dar luogo a “incapacità di partecipare

coscientemente al processo”Difficile da distinguere dalla amnesia simulata

Amnesia lacunare psicogena per il crimine

Ricordo Spontaneo

vs

Ricordo Appreso

Valutazione del ricordo

Tema Ricordo SPONTANEO Ricordo APPRESO

1.Ho acquisito da altri dell’accoltellamento 1. Ho un ricordo personale delle coltellate

2.Ho saputo in seguito dell'accoltellamento 2. Ricordo in modo distinto l’accoltellamento

3. So tramite altri delle coltellate inferte 3. Ho chiare in mente le coltellate inferte

4. Ho solo notizie indirette delle coltellate 4. Ho un ricordo diretto delle coltellate

5. Ho saputo da altri della mia azione 5. Ricordo in modo nitido la mia azione

Tentato Omicidio

Esempio di frasi

True/

London

False/

Paris

Caso 1

• ha ucciso la moglie con un cuscino

• Buco amnesico che inizia il giorno prima e finisce il giorno dopo

• Conosce il fatto nei dettagli perché ha letto la documentazione

Autobiographical IAT

• Ho una memoria vivida e genuina per il fatto VS

• Conosco perché ho letto nelle carte

•RISULTATO: Ha una memoria vivida e genuina Amnesia simulata


True/

London

False/

Paris

Caso 2

• accoltellato padre e madre

• tentato suicidio

• amnesia post-crimine

• Conosce i fatti perché ha letto la documentazione

Autobiographical IAT

• Ho una memoria vivida e genuina per il fatto VS

• Conosco perché ho letto nelle carte

•RISULTATO: Ha una memoria indiretta amnesia dissociativa genuina


• Reato d’impeto• Reazione a corto circuito

• Le intenzioni distali non sono soggette a questi effetti (premedidazione-deliberazione distale)

Psichiatria Forense

neuroscienze e libero arbitrio

Education

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motor preparation

conscious intentions

inferential processes

banks

ego depletion

libet task

approach free