Akihisa Hirota

Application of the somatic marker hypothesis to individual differences in decision making.

The somatic marker hypothesis (Damasio, Tranel, & Damasio, 1991) is a controversial theory asserting that somatic activities implicitly bias human behavior. In this study, we examined the relationship between choice behaviors in the Iowa Gambling Task and patterns of skin conductance responses (SCRs) within a healthy population. Results showed that low SCRs for appraising the monetary outcome of risky decisions were related to persistence in risky choices. Such adherence to risky decisions was not related to poor explicit knowledge about the task. On the other hand, anticipatory SCRs and the effect of them on performance were not confirmed. Our findings suggest that a variation in covert physiological appraisal underlies individual differences in decision making.

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.

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.

Skin blood flow responses during sleep by laser Doppler flowmetry

Skin surface blood flow at the fingertips was measured in a 21‐year‐old woman during sleep using laser Doppler flowmetry. Skin blood flow responses (SBFR) are transient reductions in skin blood flow of about 25 s in duration. In our subject, SBFR showed a delay time of 8–9 s from the onset of skin potential responses (SPR) and appeared more consistently than SPR. The frequency of SBFR decreased during non‐rapid eye movement sleep, especially when the sleep stage became deep. These findings indicate the validity of SBFR as a discrete index of autonomic function during sleep.