On 20 January 2015 Inga Karton will defence her doctoral thesis "Deceptive communication: the effects of transcranial magnetic stimulation and the signatures of electroencephalography" in the Council of the Faculty of the Social Sciences and Education.
Professor Talis Bachmann, University of Tartu
Associate Professor Bruno Verschuere, University of Amsterdam
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.