Neuroscienze e Libero Arbitrio

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Giuseppe Sartori
Università di Padova

Convegno "Le neuroscienze incontrano le altre discipline"
Padova, Palazzo del Bo
6 maggio 2011

Il convegno è promosso dall’Università di Padova e dal Dipartimento di Psicologia generale della stessa università, con il sostegno della Fondazione Sigma Tau e della Fondazione Giannino Bassetti.

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  • Neuroscienze e Libero Arbitrio

    1. 1. Giuseppe Sartori Università di Padova Neuroscienze e Libero Arbitrio
    2. 2. Free will and science Free will Intentions Decision-making Agency Executive control Internally vs. externally generated actions Philosophy Theology Genetics Brain or mind sciences Physics
    3. 3. Free will and conscious intentions Conscious or purposeful plan for a future action, that exists prior to and independently of action execution <ul><ul><li>Subjectively, is the proximal cause of movement (also called motor intention ) </li></ul></ul>Intention is crucial for the experience of free will. Searle (1983) distinguishes two types of intentions:
    4. 4. 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
    5. 5. Inferential processes in conscious intentions Theoretical background
    6. 6. Inferential processes in conscious intentions <ul><li>“ Reconstruction hypothesis” of intention (e.g. Dennett & Kinsbourne, 1992; Wegner, 2002) </li></ul><ul><ul><li>Based on inference </li></ul></ul><ul><ul><li>Intention is retrospectively built as the cause of the movement </li></ul></ul><ul><li>Empirical evidence </li></ul><ul><ul><li>Action consequences affect intention attribution (Kuhn & Brass, 2009) </li></ul></ul><ul><ul><li>TMS after movement shifts the W-judgment (Lau et al., 2007) </li></ul></ul><ul><ul><li>W-judgment is inferred from apparent time of response, rather than actual movement (Banks & Isham, 2009) </li></ul></ul>- + Movement onset 0 -2 s Voltage ( µV) Most studies focus on pre-movement brain processes (e.g. Libet et al., 1983; Haggard & Eimer, 1999; Soon et al., 2008) Theoretical background ?
    7. 7. Inferential processes in conscious intentions 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
    8. 8. Inferential processes in conscious intentions <ul><ul><li>Delayed auditory feedback signaling a response later than the actual one was delivered (5, 20, 40, or 60 ms) </li></ul></ul><ul><ul><li>16 participants (7 females, 19-24 years) performed a variant of the Libet task (Banks & Isham, 2009) </li></ul></ul>Responding hand not visible Methods and procedure <ul><ul><li>EEG activity was recorded (64 channels, ref mast) </li></ul></ul>
    9. 9. Inferential processes in conscious intentions <ul><li>W-judgment varied as a function of feedback delays </li></ul>Results Nae amplitude was larger for later feedbacks and associated with shifts in the W-judgment
    10. 10. <ul><li>Reported time of intention (W-judgment) is partially based on inferential processes (i.e. external feedback signaling response) </li></ul><ul><li>Action monitoring is involved in the experience of intention (Nae may reflect action-effect binding) </li></ul><ul><li>However, results cast doubts on the Libet procedure as measure of conscious intentions </li></ul><ul><ul><li>Can we exclude that participants respond as that the intention “must have taken place” sometime before the external feedback? </li></ul></ul>Inferential processes in conscious intentions Conclusions
    11. 11. Free will and science: a novel approach Free will Theology Philosophy Physics Genetics Intentions Decision-making Agency Executive control Internally vs. externally generated actions Brain or mind sciences
    12. 12. Free will and science: a novel approach Free will Theology Philosophy Physics Genetics Brain or mind sciences Behaviour
    13. 13. Free will beliefs and motor preparation Theoretical background
    14. 14. 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) Theoretical background
    15. 15. Free will beliefs and motor preparation Theoretical background Neuroscientific findings challenge the nature of free will W hat would happen if people are induced to disbelieve in free will?
    16. 16. Free will beliefs and motor preparation <ul><li>Social psychology demonstrates that it has important behavioural consequences </li></ul><ul><ul><li>Increases cheating (Vohs & Schooler, 2008) </li></ul></ul><ul><ul><li>Reduces altruistic behaviour and promotes antisocial tendencies (Baumeister et al., 2009) </li></ul></ul>Theoretical background Deterministic perspective (i.e. free will is an illusion) Ego depletion Less intentional effort into behaviour Less responsibility for own actions
    17. 17. Free will beliefs and motor preparation Hypotheses Readiness Potential (RP) Slow negative wave preceding voluntary movements Modulated by level of intentionality and mental effort. Absent or greatly reduced in automatic movements <ul><ul><li>Does disbelieving in free will alter neurophysiological processes of motor preparation? </li></ul></ul>- + Movement onset 0 -2 s Voltage ( µV)
    18. 18. Free will beliefs and 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
    19. 19. <ul><li>Free will belief manipulation </li></ul><ul><ul><li>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 </li></ul></ul>Free will beliefs and motor preparation 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
    20. 20. Free will beliefs and motor preparation <ul><ul><li>Auditory feedback signaling key press was delivered simultaneously or later than the actual response (20, 40, or 60 ms) </li></ul></ul><ul><ul><li>EEG activity was recorded (32 channels) </li></ul></ul>Methods and procedure
    21. 21. Free will beliefs and motor preparation 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” Methods and procedure
    22. 22. Free will beliefs and motor preparation 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
    23. 23. Free will beliefs and motor preparation Reduced RP amplitude in the no-free will group [F(1,28) = 4.43, p < .05, η p 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)
    24. 24. Free will beliefs and motor preparation Results Significant correlation between RP and scores on the personal FWD scale controls no-free will
    25. 25. <ul><li>Basic motor preparation processes are influenced by whether people believe in free will </li></ul><ul><li>The effect is clear before people become aware of the intention: pre-conscious level </li></ul><ul><li>The manipulation does not affect intention at a conscious level (i.e. no differences in the W-judgments) </li></ul>Free will beliefs and motor preparation Conclusions
    26. 26. Free will beliefs and motor preparation 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 belief Negative emotions?
    27. 27. <ul><li>Experience of intention is not only based on pre-action processes </li></ul><ul><ul><li>Action-effect binding does not involve only motor preparation, but also action monitoring </li></ul></ul><ul><li>Whether or not free will is an illusion, it is much better to believe in it! </li></ul><ul><ul><li>Effects on very basic brain processes </li></ul></ul>General conclusions
    28. 28. <ul><li>Reato d’impeto </li></ul><ul><li>Reazione a corto circuito </li></ul><ul><li>Le intenzioni distali non sono soggette a questi effetti (premedidazione-deliberazione distale) </li></ul>Psichiatria Forense
    29. 29. Imputabilità <ul><li>Capacità di intendere e di volere </li></ul><ul><ul><li>Nesso di causa fra stato mentale patologico e reato </li></ul></ul><ul><li>Infermità di mente </li></ul><ul><ul><li>Alterazione patologica </li></ul></ul><ul><ul><ul><li>Come si documenta? </li></ul></ul></ul><ul><ul><ul><ul><li>Approccio tassononimico - convenzionalista </li></ul></ul></ul></ul>Infermità di mente
    30. 30. PRESENZA ASSENZA CONFINE Schizofrenia Disturbo di personalità Alterazioni cerebrali VBM, DTI,ERP, fMRI Alterazioni genetiche Genetica molecolare Assenza di correlati neurali e genetici Infermità di mente
    31. 31. Imaging – VBM + DTI
    32. 32. <ul><li>Il ricordo autobiografico </li></ul><ul><li>L’intenzione nell’azione criminosa </li></ul><ul><li>Ambiti di applicazione peritali: </li></ul><ul><ul><li>Idoneità a rendere testimonianza </li></ul></ul><ul><ul><li>Vizio di mente </li></ul></ul>Due problemi centrali nel processo penale
    33. 33. <ul><li>Autobiographical memory: personal experiences, specific, long-lasting and (usually) of significance to the self-system </li></ul><ul><li>Most studies on autobiographical memory investigate how easy the information is retrieved (e.g., Crovitz & Schiffman, 1974; Kopelman, 1989). </li></ul><ul><li>No studies have been conducted in order to evaluate the truthfulness of an autobiographical event. </li></ul>Autobiographical memory: methods
    34. 34. <ul><li>Autobiographical IAT </li></ul><ul><li>C omputerizzato </li></ul><ul><li>Richiede due memorie autobiografiche alternative (es. porta aperta vs porta chiusa ) </li></ul><ul><li>Accuratezza diagnostica circa 92% </li></ul><ul><li>Criteri DAUBERT </li></ul>Caratteristcihe dello IAT per memory-detection
    35. 35. The Autobiographical-IAT <ul><li>The aIAT has been validated in a series of experiments: </li></ul><ul><li>Card aIAT </li></ul><ul><li>Mock Crime aIAT </li></ul><ul><li>Holiday aIAT </li></ul><ul><li>Suspension of driving license aIAT </li></ul>
    36. 36. 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 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” TRUE FALSE “ I'm in front of a computer” “I'm in front of a television” CARD 7 CARD 4 “ I saw the card 7” “I saw the card 4”
    37. 37. Card experiment Mock Crime experiment Driving license experiment <ul><li>Facilitating effect due to pairing of associated concepts </li></ul>Card IAT: results
    38. 38. Accuratezza IAT Relazione fra il valore del D-IAT e accuratezza diagnostica Dati di 5 esperimenti per un totale di 320 soggetti
    39. 39. Caratteristiche IAT per memory detection <ul><li>Probabilità di diagnosi corretta </li></ul><ul><li>Accuratezza media= 92% </li></ul>
    40. 40. <ul><li>Holiday aIAT </li></ul><ul><li>2 Card aIAT </li></ul><ul><li>10 Card aIAT </li></ul><ul><li>non-faking group: standard IAT instructions; </li></ul><ul><li>naïve-faking group: beat the memory detector, and to hide their true autobiographical memory to the experimenter; </li></ul><ul><li>instructed-faking group: “slow down” on the congruent block and “speed up” in the incongruent block (Fiedler & Bluemke, 2005) ‏ . </li></ul>
    41. 41. Results : Naïve fakers cannot fake the aIAT Instructed fakers are faster in the Incongruent block than the Congruent block. Detecting fakers
    42. 42. <ul><li>AUC : 0.88 </li></ul><ul><li>Conclusion : it is possible to identify subjects that tried to fake the aIAT from non fakers . </li></ul><ul><li>Difference between single blocks (1, 2, and 4) and double blocks (3, 5) is larger in fakers than in non-fakers </li></ul>Algorithm for detecting fakers
    43. 43. Method Results It is possible to identify the participants’ real intentions Intention detection Journal of Cognitive Neuroscience 2011 TRUE 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” TRUE FALSE “ I'm in front of a computer” “I'm in front of a television” False Intention True Intention “ I will sleep in Milan” “I will sleep in Padua”
    44. 44. Collocazione temporale dell ’ evento Programmato Casuale Detecting prior intentions
    45. 45. Esempio di incontro intenzionale <ul><li>Soggetto 6: incontro intenzionale con Franco per ritrovarsi dopo tanto tempo. </li></ul><ul><li>Frasi a-IAT </li></ul><ul><li>Incontro intenzionale: </li></ul><ul><li>Ho telefonato a Franco per vederci </li></ul><ul><li>Ho organizzato un incontro con Franco </li></ul><ul><li>Volevo riprendere i contatti con Franco </li></ul><ul><li>Volevo incontrare Franco da tempo </li></ul><ul><li>Ho fissato l ’ incontro a casa sua </li></ul><ul><li>Incontro casuale: </li></ul><ul><li>Ho incontrato casualmente Franco </li></ul><ul><li>Ho incrociato Franco facendo la spesa </li></ul><ul><li>Senza volerlo ho incontrato Franco </li></ul><ul><li>Per caso mi sono imbattuto in Franco </li></ul><ul><li>Ho inaspettatamente visto Franco </li></ul>Detecting prior intentions
    46. 46. Esempio di incontro casuale <ul><li>Soggetto 1: incontro casuale con Patrizia al supermercato. </li></ul><ul><li>Incontro casuale: </li></ul><ul><li>Ho incrociato per caso Patrizia </li></ul><ul><li>Al supermercato ho visto per caso Patrizia </li></ul><ul><li>Venerdì all ’ improvviso ho trovato Patrizia </li></ul><ul><li>Inaspettatamente ho incontrato Patrizia </li></ul><ul><li>Mi si è avvicinata casualmente Patrizia </li></ul><ul><li>Incontro intenzionale: </li></ul><ul><li>Volevo vedere Patrizia </li></ul><ul><li>Ho inviato un sms a Patrizia </li></ul><ul><li>Ho chiesto a Patrizia di incontrarci </li></ul><ul><li>Ho fissato un appuntamento con Patrizia </li></ul><ul><li>Alle 18 dovevo vedere Patrizia </li></ul>Detecting prior intentions
    47. 47. INCONTRO INTENZIONALE CONGRUENT= VERO/INTENZIONALE INCONGRUENT= VERO/CASUALE Incontro intenzionale
    48. 48. Numero soggetti con incontro intenzionale classificati correttamente: 12/12 (1/12 appena sopra soglia) Incontro intenzionale
    49. 49. INCONTRO CASUALE CONGRUENT= VERO/INTENZIONALE INCONGRUENT= VERO/CASUALE congruent incongruent Incontro casuale
    50. 50. <ul><li>Problematiche forensi </li></ul><ul><li>E’ lamentata molto di frequente </li></ul><ul><li>Se provata dar luogo a “incapacità di partecipare coscientemente al processo” </li></ul><ul><li>Difficile da distinguere dalla amnesia simulata </li></ul>Amnesia lacunare psicogena per il crimine
    51. 51. Ricordo Spontaneo vs Ricordo Appreso Valutazione del ricordo
    52. 52. Esempio di frasi
    53. 53. True/ London False/ Paris <ul><li>Caso 1 </li></ul><ul><li>ha ucciso la moglie con un cuscino </li></ul><ul><li>Buco amnesico che inizia il giorno prima e finisce il giorno dopo </li></ul><ul><li>Conosce il fatto nei dettagli perché ha letto la documentazione </li></ul><ul><li>Autobiographical IAT </li></ul><ul><li>Ho una memoria vivida e genuina per il fatto VS </li></ul><ul><li>Conosco perché ho letto nelle carte </li></ul><ul><li>RISULTATO: Ha una memoria vivida e genuina  Amnesia simulata </li></ul>Amnesia lacunare psicogena per il crimine
    54. 54. True/ London False/ Paris <ul><li>Caso 2 </li></ul><ul><li>accoltellato padre e madre </li></ul><ul><li>tentato suicidio </li></ul><ul><li>amnesia post-crimine </li></ul><ul><li>Conosce i fatti perché ha letto la documentazione </li></ul><ul><li>Autobiographical IAT </li></ul><ul><li>Ho una memoria vivida e genuina per il fatto VS </li></ul><ul><li>Conosco perché ho letto nelle carte </li></ul><ul><li>RISULTATO: Ha una memoria indiretta  amnesia dissociativa genuina </li></ul>Amnesia lacunare psicogena per il crimine
    55. 55. <ul><li>Reato d’impeto </li></ul><ul><li>Reazione a corto circuito </li></ul><ul><li>Le intenzioni distali non sono soggette a questi effetti (premedidazione-deliberazione distale) </li></ul>Psichiatria Forense

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