‘Is this your card?’ Behavioural Inhibition System (BIS) influence on EEG Theta during Guilty Knowledge Task

Prior, Amy (2014) ‘Is this your card?’ Behavioural Inhibition System (BIS) influence on EEG Theta during Guilty Knowledge Task. University of Portsmouth. (Unpublished)

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Abstract

The act of lying is suggested to be cognitively demanding, since it requires inhibition of the truth, and generation of a new response. Increased cognitive load influences brain activity; therefore the distinction between lies and truths should be able to be differentiated by electroencephalography (EEG). Increased EEG theta activation at frontal brain regions and decreased EEG alpha activation are proposed to be a result of increased task demands. Additionally, activation of the Behavioural Inhibition System is suggested to increase theta rhythm. The assumption was made that the BIS would be activated when an individual was put in a state of conflict induced by deception, thus differentiating between low and high sampled participants by increased EEG theta activity. Furthermore, explorative research was conducted into changes in EEG activity during initial reaction to guilty knowledge stimuli. An increase in alpha waveband activity was hypothesised based on the findings of novel research concerning Guilty Knowledge Task and EEG recordings. For the task 132 participants were pre-screened on the Carver and White (1994) BIS/BAS questionnaire to measure trait levels of BIS activation. The 19 lowest scoring participants were assigned to the low BIS category, whilst the top 20 were assigned to the high BIS category. EEG was recorded (14 electrodes) whilst participants underwent the modified Guilty Knowledge Task, denying the identity of a concealed card, whilst also being shown control and irrelevant cards. A frequency analysis was conducted with EEG data considered from 4-28 Hz. This study found that extreme sampled BIS activation did not appear to differentiate between participants using EEG theta. However a decrease in theta activity was found during participants’ initial reaction to guilty stimuli and in anticipation of telling a lie. No effects of EEG alpha were found. The finding that EEG recordings can differentiate the guilty from the innocent using their guilty knowledge could lead to formulation of new EEG deception detection techniques in the future.