The concealed information test (CIT) is a lie detection test used in criminal investigation. It has been suggested that the experimental variables known to increase the late positive component (LPC), that is, a type of event-related potential (ERP) for the relevant item in the CIT, depending on the participants' recognition of it . However, participants not only recognize the relevant item in the actual CIT but also have to engage in complicated mental activity in order to conceal their recognition. Preceding research does not clarify whether the mental activity affects the LPC in the CIT. This study investigated the mental factor that determines the LPC in the CIT. In order to examine this, we divided the LPC in the CIT into P300 and positive slow wave (PSW).
Chapter 1 presents a review of the relevant literature of the CIT and the LPC based CIT. Chapter 2 demonstrates that PSW for the intention of concealment of recognition was larger than for no intention in the CIT. However, this was also observed with regard to the intention of transmitting. Chapter 3 investigates the effect of additional processing in CIT. Chapter 4 investigates whether the stimulus frequency of the relevant items affect the LPC in CIT. P300 was increased for the stimulus significant of the relevant item rather than for stimulus frequency. Chapter 5 demonstrates the effects of stimulus frequency of the relevant item and target item in CIT. In Chapter 6, on the basis of the results presented in each of the preceding chapters, a model describing the factor that determines P300 and PSW in CIT is presented.