Area measure of skin conductance in the Concealed Information Test.

Skin conductance (SC) is one of the indices commonly used in the autonomic Concealed Information Test (CIT), but SC amplitude is sometimes difficult to quantify. This study investigated the applicability of SC area to the CIT as an unambiguous measure of SC. Secondary analyses of an existing dataset indicated that SC area could be used to classify examinees according to their knowledge status, although the equivalence of its performance with the SC amplitude was inconclusive. Classification performance was best when the SC signal was converted to the difference from question onset and summed over 10 s after question onset. SC area produced relatively consistent evaluations of differential responses based on the amplitude for inter-item comparisons. In addition, the classification performance of SC area exceeded the chance level even for participants who showed few measurable amplitudes (low-responsive participants). A possible implication is that a tonic increase in SC occurred in response to the relevant question even in low-responsive participants, who are traditionally excluded from analysis. The use of SC area might contribute to more impartial data evaluation and broader application of the CIT. These results indicate that SC area can be used as an alternative measure of SC in the CIT.

Selective memory detection: Context-dependent stimulus significance in the concealed information test.

Previous studies have posited that the significance of a crime-relevant item in a question produces differential physiological responses in the Concealed Information Test (CIT). However, this term is equivocal and needs to be clarified in order to strengthen the theoretical underpinnings of the CIT. The present study examined the hypothesis that differential responding depends on the examinee's understanding of which item in a question is relevant to a given context. Participants performed a mock theft task, in which they were instructed to steal one item from each of two different locations. An identical CIT question asking about each stolen item was presented under different location contexts while skin conductance response, heart rate, and respiratory activity were recorded. Results indicated that only the relevant item specified by the context of the instruction elicited reliable differential physiological responses. This finding implies that differential responding in the CIT is flexible and context-dependent, and that specifying the subject of a given question is important for detecting crime-relevant memories in practical criminal investigations.

The Use of Pupillometry in Autobiographical Implicit Association Test.

The Autobiographical Implicit Association Test (aIAT) is a reaction time-based methodology to assess one's recognition of the truth value of propositions about an autobiographical episode. This study introduced pupillometry to examine its utility as an additional measure of aIAT. Participants blindly chose one of two cards and memorized it. They then underwent the aIAT to assess the cards they chose. The pupil diameter was larger in the block in which sentences related to the chosen card shared the same response key with sentences describing false events than the block in which sentences related to the chosen card shared the same response key with true-event sentences. Although preliminary, pupil measurement also yielded high efficiency in discriminating the chosen card. These results indicate that pupillometry can be used as a measure of aIAT.

Different psychophysiological responses induced by a stimulus change during the orienting task and the Concealed Information Test.

The orienting response (OR) account of the Concealed Information Test (CIT) posits that physiological responses to CIT items are components of the OR. Physiological variations within a stimulus sequence were investigated in an OR task (Study 1) and the CIT (Study 2). In Study 1, an unexpected increase in tone intensity was introduced after repeated standard tone presentations. The deviant tone elicited a large skin conductance response (SCR), heightened vascular tone, and self-reported surprise and also increased skin conductance level, self-reported arousal, and sustained vascular tone thereafter. In Study 2, the deviant relevant item presentation elicited a larger SCR and greater surprise compared with the frequent irrelevant item presentation, whereas vascular tone and self-reported arousal dropped after presentation of the relevant item. These results indicate that although phasic responses to a deviant stimulus were similar in both tasks, tonic variations following the stimulus change differed. Possible implications are discussed.

Broadening the Use of the Concealed Information Test in the Field.

Japan is the only country where the polygraph with the concealed information test (CIT) is widely applied to criminal investigations. The CIT can reveal whether an examinee has knowledge of specific details of a crime. Furthermore, the CIT can extract crime-relevant information that investigative organizations have not yet uncovered. This article introduces how Japanese polygraphers take advantage of the CIT in criminal investigations. We also describe how polygraphs with the CIT are currently used in court. Then we propose statistical discrimination methods that can be easily applied to CIT interpretation in the field. Appropriate application of the statistical values is discussed. We hope that this article will facilitate more active use of the CIT outside Japan.

Hierarchical Bayesian models for the autonomic-based concealed information test.

The concealed information test (CIT) is a psychophysiological memory detection technique for examining whether an examinee recognizes crime-relevant information. In current statistical analysis practice, the autonomic responses are usually transformed into Z scores within individuals to remove inter- and intra-individual variability. However, this conventional procedure leads to overestimation of the effect size, specifically the standardized mean difference of the autonomic responses between the crime-relevant information and the crime-irrelevant information. In this study, we attempted to resolve this problem by modeling inter- and intra-individual variability directly using hierarchical Bayesian modeling. Five models were constructed and applied to CIT data obtained from 167 participants. The validity of the CIT was confirmed using Bayesian estimates of the effect sizes, which are more accurate and interpretable than conventional effect sizes. Moreover, hierarchical Bayesian modeling provided information that is not available from the conventional statistical analysis procedure.

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 Rovner's (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 Rovner's (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.

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.

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.

Identifying concealment-related responses in the concealed information test.

The concealed information test (CIT) assesses an examinee's 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.

Event-related potentials increase the discrimination performance of the autonomic-based concealed information test.

The concealed information test (CIT) assesses an examinee's crime-relevant memory on the basis of physiological differences between crime-relevant and irrelevant items. The CIT based on autonomic measures has been used for criminal investigations, while the CIT based on event-related potentials (ERPs) has been suggested as a useful alternative. To combine these two methods, we developed a quantification method of ERPs measured in the autonomic-based CIT where each item was repeated only 5 times. Results showed that the peak amplitude of the ERP difference wave between crime-relevant and irrelevant items could discriminate between guilty and innocent participants effectively even when only 5 trials were used for averaging. This ERP measure could detect some participants who were missed by the autonomic measures. Combining the ERP and autonomic measures significantly improved the discrimination performance of the autonomic-based CIT.

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

The Concealed Information Test (CIT) assesses an examinee's 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.

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.

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 individual's 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.

[Effects of arousal level on the physiological responding on the Concealed Information Test].

This study examined effects of arousal level on the physiological responses in a polygraph examination using the Concealed Information Test (CIT). Thirty-nine healthy college students were tested with or without evaluative observation. Electrodermal activity, blood pressure, heart rate, normalized pulse volume, and respiration were recorded. Observation elevated participants' arousal level, which was manifested in self-reports, high skin conductance level, and low normalized pulse volume (i.e., vasoconstriction). However, differential reactivity to critical and non-critical items on the physiological measures was less affected by observation. These results suggested that participants' arousal level has little effect on differential physiological reactivity on the CIT.

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.

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.