Deceptive communication: the effects of transcranial magnetic stimulation and the signatures of electroencephalography
Date
2014-12-17
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Abstract
Valetamine on paraku meie igapäevase elu osaks. Üldistades võib öelda, et kõik inimesed valetavad, kas siis mõtlematult või teadlikult. Viimane nendest – tahtlik vale – võib teatud juhtudel muutuda aga probleemiks, nimelt juriidiliseks probleemiks. See, kui tõesed on inimeste ütlused, mõjutab otseselt õigusemõistmise protsesse. Palju räägitakse tunnistajate ütluste tõepärasusest, mis väljendub selles, mida ja kuidas isik varemkogetust mäletab. Sellised ütlused ei pruugi olla tõelevastavad. Enamasti on siinjuures tegemist tahtmatult eksliku väite esitamisega. Samas pole harvad ka juhud, kus eksitav väide esitatakse teadlikult. Pole raske ette kujutada, millal ja milleks on vaja inimestel tahtlikult valetada. Selleks, et varjata oma süüd, midagi sellist, mille üles tunnistamine on sotsiaalselt vastuvõetamatu ja toob kaasa soovimatud tagajärjed: halvakspanust kuni vanglakaristuseni välja. Arusaadavalt iseloomustab erinevaid inimesi erinev nö valetamislävi, individuaalne valmidus ja võime valetada. Valetamiskalduvus varieerub ka ühel ja samal inimesel sõltuvalt olukorrast ja seisundist. Seda, mil määral inimesed valetavad (või siis jätavad tõe rääkimata), ja kas selle määraga saab ka manipuleerida ning kuidas ebasiirus väljendub psühhofüsioloogilistes ilmingutes, antud töös uuritigi. On teada, et psüühiline seisund ning isiku individuaalsed omadused (sh emotsionaalsus) võivad mõjutada seda, kas ja kuivõrd edukas on keegi valetamises. Mainitud varieeruvus on ka polügraaftestimise ebapiisava usaldusväärsuse põhjuseks. Selleks, et paremini mõista, millised aju osad ja millisel moel on kaasa haaratud petukäitumisse, on oluline mõjutada närvisüsteemi tegevust ja vaadata, kas selle tagajärjel ka vastav käitumine muutub. Seda väitekirjas uuritigi. Töö käigus ilmnes, et inimeste petukäitumist (sj olukorras, kus otseselt puudub vajadus ja/või instruktsioon valetada) saab mõjutada aju funktsionaalse seisundi manipuleerimisega transkraniaalse magnetstimulatsiooni abil. Teadaolevalt on aju suurte poolkerade otsmikusagara eesmine-selgmine-külgmine piirkond kaasa haaratud petukäitumisse. Kui seda piirkonda mõjutada pidurdavat toimet avaldavate nn väsitavate magnetimpulssidega, siis parema poolkera mõjutamise järel on keerulisem tõest väidet tagasi hoida (isikud valetavad vähem). Kui aga pidurdada vasaku poolkera vastavat piirkonda, siis õnnestub tõese väite tagasihoidmine paremini (isikud valetavad rohkem). Kui aga kasutada väsitamise režiimi asemel ergastamise režiimi (ajutegevuse aktiviseerimist), siis parema poolkera mõjutamisel õnnestus (vastupidiselt väsitamisele) valetamine katseisikutel paremini. Tingimustes, kus spontaanne tõe rääkimine on asendatud teadliku motiveeritud valetamisega, väsitamise režiim nii selget ja otsest mõju petukäitumisele ei avalda. Küll aga teeb seda ergastamine: vasaku poolkera ergastamisel valetamise määr väheneb ja parema poolkera puhul pisut suureneb. Käesoleva töö EEG-põhine osa kinnitas teadaolevat tõsiasja, et ajus valetamise ajal toimuvate bioelektriliste protsesside valetamisega seostuvaid signatuure on põhimõtteliselt võimalik tuvastada. Uuring näitas ka, et valetamise tuvastamiste usaldusväärsus sõltub sellest, kuidas kogu protseduur on üles ehitatud: elukaugemates ja vähema kriitilisusega olukordades on tuvastamismeetodi tundlikkus väiksem võrreldes elulähedasemate ja suurema kriitilisuse astmega olukordadega. Lisandus EEG-põhiste meetodite suhtes uudne teadmine, et madala sagedusega magnetimpulssidega ajukoort mõjutades on võimalik valetamisele tundlike signatuuride väljendumist muuta: vastused kriitilisele (valetamise objektiks olevale) stiimulile muutuvad sarnasemaks vastustega neutraalsetele (asjasse mittepuutuvatele) stiimulitele. Kokkuvõtvalt saab öelda, et petukäitumises mängib olulist rolli inimeste eesmine otsmine ajukoor, mida kinnitab asjaolu, et selle ja sellega seotud muude keskuste funktsionaalsust mõjutades ilmnevad ka vastavad muutused inimeste käitumises ja selle psühhofüsioloogilistes signatuurides.
Lying is an inevitable part of our daily lives. All people produce non-veridical statements, of which some are intentional lies. The latter may, in certain instances, become a problem, namely a legal problem. Truthfulness of testimony directly affects the course and outcomes of the process of justice. Much has been discussed about the veracity of eyewitness testimony, with complaints and suspicion about statement validity and reliability which are the matter of how well and how one remembers facts. Legal statements by witness or suspect often are inconsistent with true facts. In most cases, these are candid, however erroneous beliefs void of intended lying; yet sometimes these are deliberate deceptive communications. It is not hard to imagine when and why one feels necessary to produce a deliberate lie or avoid confession. It happens in order to conceal one’s guilt and avoid disclosing something, adherence to which is socially unacceptable and brings unwanted consequences, varying from bad bets (frowning) up to imprisonment. The propensity and readiness to lie varies between individual subjects and between situations the same subject happens to be in. This doctoral thesis studies the extent to which people lie about observed objects in a behavioural task. Importantly, it studies whether a respective lying rate and the psychophysiological signatures of lying can be manipulated by non-invasive brain-stimulation methods. It is well known that psychological state (including affective state) can affect whether and to what extent one lies successfully and whether objective physiological signatures are indicative of deception. Individual differences in trait and state variables make it difficult to have reliable lie detection methods. This is also the reason why reliability of polygraph testing remains insufficient. It is important to study deception by causally influencing the activity of the nervous system and see if the behaviour changes as a result of this kind of intervention. It helps to better ascertain what parts of the brain are involved and in what way in the deceptive behaviour. In our studies, we followed this strategy, capitalising on the neuronavigated transcranial magnetic stimulation method. In the process, we discovered that human deceptive behaviour can be influenced by this kind of noninvasive brain stimulation. The cortex of cerebral hemispheres in the frontal lobe areas is known to be involved in deceptive behaviour. Depending on the locus and mode of perturbing cortical stimulation it was possible either to increase or decrease the relative rate of untruthful naming responses. The so-called exhaustion or disruption of the left hemisphere dorsolateral prefrontal cortex helped subjects to better succeed in holding back the truthful response (i.e., to lie more) while exhausting the right hemisphere corresponding area lead to an opposite effect (i.e., less lying). However, if the excitation of the right dorsolateral prefrontal cortex was used instead of the exhaustion, people managed to lie more compared to the disrupting manipulation of this hemisphere. If, however we replaced the task of spontaneous truth-telling with more strongly motivated lying, then the exhaustion mode of stimulation did not have so clear and a direct impact on deceptive behaviour. While the excitation of the left hemisphere decreased lying rate, only a slight and nonsignificant increase in lying was observed when the right hemisphere was stimulated. The present work also confirmed the known facts that the level of expression of certain bioelectrical brain-potential components can be used as signatures of lying. We also showed that the brain-potential based lie-detection reliability depends on how the whole process is structured: in the less life-like and less critical situation the sensitivity of the method of detection is lower compared to the situation utilising a larger degree of criticality of the stimuli and circumstances closer to real life situations. A novel finding also consists in the effect of brain stimulation on the psychophysiological deception signatures: the low-frequency magnetic stimulation of the cerebral cortex changed the level of expression of the lie-detection signatures. The brain responses to the critical stimuli (objects of lying) became more similar to the responses to neutral (non-relevant) stimuli. Summarising the main results of this thesis-work it can be concluded that frontal cortex plays an important role in deceptive behaviour and the propensity to lie and the brain-process signatures of lying can in principle be manipulated by non-invasive brain stimulation targeted at the dorsolateral prefrontal areas. It is also apparent that sensitivity of the electrophysiological brain-process signatures of deception to critical stimuli considerably varies between subjects.
Lying is an inevitable part of our daily lives. All people produce non-veridical statements, of which some are intentional lies. The latter may, in certain instances, become a problem, namely a legal problem. Truthfulness of testimony directly affects the course and outcomes of the process of justice. Much has been discussed about the veracity of eyewitness testimony, with complaints and suspicion about statement validity and reliability which are the matter of how well and how one remembers facts. Legal statements by witness or suspect often are inconsistent with true facts. In most cases, these are candid, however erroneous beliefs void of intended lying; yet sometimes these are deliberate deceptive communications. It is not hard to imagine when and why one feels necessary to produce a deliberate lie or avoid confession. It happens in order to conceal one’s guilt and avoid disclosing something, adherence to which is socially unacceptable and brings unwanted consequences, varying from bad bets (frowning) up to imprisonment. The propensity and readiness to lie varies between individual subjects and between situations the same subject happens to be in. This doctoral thesis studies the extent to which people lie about observed objects in a behavioural task. Importantly, it studies whether a respective lying rate and the psychophysiological signatures of lying can be manipulated by non-invasive brain-stimulation methods. It is well known that psychological state (including affective state) can affect whether and to what extent one lies successfully and whether objective physiological signatures are indicative of deception. Individual differences in trait and state variables make it difficult to have reliable lie detection methods. This is also the reason why reliability of polygraph testing remains insufficient. It is important to study deception by causally influencing the activity of the nervous system and see if the behaviour changes as a result of this kind of intervention. It helps to better ascertain what parts of the brain are involved and in what way in the deceptive behaviour. In our studies, we followed this strategy, capitalising on the neuronavigated transcranial magnetic stimulation method. In the process, we discovered that human deceptive behaviour can be influenced by this kind of noninvasive brain stimulation. The cortex of cerebral hemispheres in the frontal lobe areas is known to be involved in deceptive behaviour. Depending on the locus and mode of perturbing cortical stimulation it was possible either to increase or decrease the relative rate of untruthful naming responses. The so-called exhaustion or disruption of the left hemisphere dorsolateral prefrontal cortex helped subjects to better succeed in holding back the truthful response (i.e., to lie more) while exhausting the right hemisphere corresponding area lead to an opposite effect (i.e., less lying). However, if the excitation of the right dorsolateral prefrontal cortex was used instead of the exhaustion, people managed to lie more compared to the disrupting manipulation of this hemisphere. If, however we replaced the task of spontaneous truth-telling with more strongly motivated lying, then the exhaustion mode of stimulation did not have so clear and a direct impact on deceptive behaviour. While the excitation of the left hemisphere decreased lying rate, only a slight and nonsignificant increase in lying was observed when the right hemisphere was stimulated. The present work also confirmed the known facts that the level of expression of certain bioelectrical brain-potential components can be used as signatures of lying. We also showed that the brain-potential based lie-detection reliability depends on how the whole process is structured: in the less life-like and less critical situation the sensitivity of the method of detection is lower compared to the situation utilising a larger degree of criticality of the stimuli and circumstances closer to real life situations. A novel finding also consists in the effect of brain stimulation on the psychophysiological deception signatures: the low-frequency magnetic stimulation of the cerebral cortex changed the level of expression of the lie-detection signatures. The brain responses to the critical stimuli (objects of lying) became more similar to the responses to neutral (non-relevant) stimuli. Summarising the main results of this thesis-work it can be concluded that frontal cortex plays an important role in deceptive behaviour and the propensity to lie and the brain-process signatures of lying can in principle be manipulated by non-invasive brain stimulation targeted at the dorsolateral prefrontal areas. It is also apparent that sensitivity of the electrophysiological brain-process signatures of deception to critical stimuli considerably varies between subjects.
Description
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Keywords
valetamine, pettus, sotsiaalne käitumine, ajutalitlus, suurajukoor, stimulatsioon, manipuleerimine, transkraniaalne magnetstimulatsioon, elektroentsefalograafia, eksperimentaalpsühholoogia, psühhofüsioloogia, kognitiivne psühholoogia, neuropsühholoogia, lying, deceit, social behavior, brain function, cerebral cortex, stimulation, manipulation, transcranial magnetic stimulation, electroencephalography, experimental psychology, psychophysiology, cognitive psychology, neuropsychology