Tokihiro Ogawa

Event-related brain potentials during the standard autonomic-based concealed information test

The concealed information test (CIT) has been used to detect information that examinees possess by means of their autonomic responses. However, the central activities related to these autonomic responses remain unclear. In this study, we simultaneously recorded 128-ch event-related potentials (ERPs) and various autonomic responses (heart rate, respiratory rate, respiratory amplitude, cutaneous blood flow, and skin conductance response) to a critical item (i.e., the item that participants memorized) and to non-critical items (i.e., items other than the critical item) using the standard protocol of the autonomic-based CIT. A topographic analysis of variance and a temporal-spatial principal component analysis revealed that the critical item elicited a larger negative potential (N2b, 205-298 ms) at central regions and a larger positive potential (positive slow wave, 502-744 ms) at parieto-occipital regions, compared to the non-critical items. Correlation analysis across 21 participants showed a significant correlation between N2b increase and heart rate deceleration in response to critical items compared to non-critical items, but there were no autonomic correlates of the positive slow wave. The results suggest that at least two brain processes are involved in the autonomic-based CIT: The first is an attentional-orienting process that facilitates the processing of critical items, to which heart rate deceleration was linked, and the second is an additional process after the identification of critical items.

A new discrimination method for the Concealed Information Test using pretest data and within-individual comparisons.

A latent class discrimination method is proposed for analyzing autonomic responses on the concealed information test. Because there are significant individual differences in autonomic responses, individual response patterns are estimated on the pretest. Then an appropriate discriminant formula for the response pattern of each individual is applied to the CIT test results. The probability that the individual concealed information is calculated by comparing the discriminant formula value of the crime-related item to that of non-crime-related items. The discrimination performance of the latent class discrimination method was higher than those of the logistic regression method and the discriminant analysis method in an experimental demonstration applying the three methods to the same data set.

Identifying concealment-related responses in the concealed information test

The concealed information test (CIT) assesses an examinees recognition of a crime-relevant item using physiological measures. However, a guilty examinee not only recognizes the crime-relevant item but also conceals the recognition intentionally. In this study, we attempted to identify the effect of concealing the recognition on event-related potentials and autonomic responses. After committing a mock theft of two items, 30 participants received two CITs: one for an item that they had to conceal, and the other for an item that they had disclosed. N2, P3, heart rate, skin conductance, and cutaneous blood flow differed between crime-relevant and irrelevant items in both CITs. In contrast, late positive potential and respiration differed between crime-relevant and irrelevant items only when the examinee needed to conceal. The former measures appear to be related to orienting process, whereas the latter to controlled process related to concealment.

Within-individual discrimination on the Concealed Information Test using dynamic mixture modeling.

Whether an examinee has information about a crime is determined by the Concealed Information Test based on autonomic differences between the crime-related item and other control items. Multivariate quantitative statistical methods have been proposed for this determination. However, these require specific databases of responses, which are problematic for field application. Alternative methods, using only an individuals data, are preferable, but traditionally such within-individual approaches have limitations because of small data sample size. The present study proposes a new within-individual judgment method, the hidden Markov discrimination method, in which time series-data are modeled with dynamic mixture distributions. This method was applied to experimental data and showed sufficient potential in discriminating guilty from innocent examinees in a mock theft experiment compared with performance of previous methods.

Improved method for calculating the respiratory line length in the Concealed Information Test.

The Concealed Information Test (CIT) assesses an examinees knowledge about a crime based on response differences between crime-relevant and crime-irrelevant items. One effective measure in the CIT is the respiration line length, which is the average of the moving distances of the respiration curve in a specified time interval after the item onset. However, the moving distance differs between parts of a respiratory cycle. As a result, the calculated respiration line length is biased by how the parts of the respiratory cycles are included in the time interval. To resolve this problem, we propose a weighted average method, which calculates the respiration line length per cycle and weights it with the proportion that the cycle occupies in the time interval. Simulation results indicated that the weighted average method removes the bias of respiration line lengths compared to the original method. The results of experimental CIT data demonstrated that the weighted average method significantly increased the discrimination performance as compared with the original method. The weighted average method is a promising method for assessing respiration changes in response to question items more accurately, which improves the respiration-based discrimination performance of the CIT.

Using pretest data to screen low-reactivity individuals in the autonomic-based concealed information test.

The concealed information test (CIT) can be used to assess whether an individual possesses crime-related information. However, its discrimination performance has room for improvement. We examined whether screening out participants who do not respond distinctively on a pretest improves the diagnosticity of a mock-crime CIT. Before conducting the CIT, we gave a pretest to 152 participants, 80 of whom were assigned as guilty. Pretest screening significantly improved the diagnostic value of the mock-crime CIT; however, it also led to a substantial number of undiagnosed participants (33.6%). Pretest screening holds promise, but its application would benefit from dedicated measures for screening out participants.

The Comparison Question Test versus the Concealed Information Test? That was the question in Japan: a comment on Palmatier and Rovner (2015).

Palmatier and Rovner (2015) discussed the possible interplay of two major methods of polygraph examination, the Comparison Question Test (CQT) and the Concealed Information Test (CIT). In this comment, we argue that such an attempt overlooks fundamental differences between the two methods. Specifically, both methods differ in their criterion variables; detecting deception versus detecting memory traces. This difference can lead to a different evaluation concerning their outcomes within a forensic context. However, Palmatier and Rovners (2015) attempt may blur the distinction between the two methods. Furthermore, at least for the present, it is difficult to give a unified explanation of physiological responses in the CQT and CIT based on the preliminary process theory of the orienting response. In sum, Palmatier and Rovners (2015) paper may add further confusion to the research and practice of polygraph testing. Additionally, their paper has no relevance to the current practice of Japanese polygraph examination, because Japanese law enforcement uses only the CIT for memory detection in real-life criminal investigations.

Systematic changes in tonic physiological activities during the Concealed Information Test

Many studies on the Concealed Information Test have focused on phasic physiological changes that are temporally locked to stimulus presentation. However, little is known about changes in tonic, basal physiological levels throughout a stimulus series. This study focused on changes in tonic physiological activities during the CIT. Thirty-nine participants carried out a mock theft and subsequently received a CIT. Skin conductance, heart rate, and normalized pulse volume (NPV) were recorded. The pre-stimulus physiological level of these measures throughout the CIT series was compared across a question series with different serial positions of the relevant item. Results showed that changes in the pre-stimulus level differed depending on the serial position of the relevant item. Skin conductance declined throughout the series, but showed a transient increase after relevant item presentation. Heart rate was relatively constant throughout the series, but decreased after relevant item presentation. NPV continued to decrease until the relevant item, but increased thereafter, indicating a pattern similar to the classic Peak of Tension concept. In addition, the pre-stimulus NPV showed a significant relevant-irrelevant difference. Theoretical and practical implications of these findings are discussed.

Event-related brain potential in responses to social messages via human faces.

In two experiments participants were presented a sequence of facial photographs to examine effects of pleasantness of facial expressions, namely, pleasant and unpleasant, and task relevance on P300 component of event-related brain potentials in the 3-stimulus version of the oddball task. Exp. 1 showed that, although the amplitudes of P300 were the largest in response to task-relevant target stimuli and moderate in response to task-irrelevant nontargets, the Pleasantness of stimuli did not affect the amplitudes of P300 when the stimuli were task-relevant or irrelevant. Data in Exp. 2 suggested that the emotional significance rather than physical characteristics of stimuli might be responsible for generation of P300 by task-irrelevant nontargets.