The validity of psychophysiological detection of information with the Guilty Knowledge Test: A meta-analytic review.

The authors performed a meta-analysis based on 169 conditions, gathered from 80 laboratory studies, to estimate the validity of the Guilty Knowledge Test (GKT) with the electrodermal measure. The over-all average effect size was 1.55, but there were considerable variations among studies. In particular, mock-crime studies produced the highest average effect size (2.09). Three additional moderators, were identified: Motivational instructions, deceptive ("no") verbal responses, and the use of at least 5 questions were associated with enhanced validity. Finally, a set of 10 studies that best approximated applications of the GKT under optimal conditions produced an average effect size of 3.12. The authors discuss factors that might limit the generalizability of these results and recommend further research of the GKT in realistic setups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A method for evaluating the use of the polygraph in a real-life situation.

15 males (mean age 29.2 yrs) participated in an experiment to evaluate the polygraph in a real-life situation; 2 Ss had actually cheated on a test. All Ss went through a standard polygraph test using the control questions method. This procedure guarantees the objective identification of "liars" without jeopardizing the real-life appearance of the experimental situation. Each S was evaluated by 3 polygraphers: One had access to the polygraph charts only, one observed the S's behavior but not his charts, and a third had both kinds of information. The evaluations of all 3 polygraphers were compared with the criterion. Evaluations based on both behavior observation and physiological charts were superior to those based on either type of information alone. However, evaluations based on the physiological information alone were not superior to those based on the behavioral information alone. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection measures in real-life criminal guilty knowledge tests.

Provides a 1st attempt to compare the validity of the respiration line length (RLL) and skin resistance response (SRR) amplitude in real-life criminal guilty knowledge tests (GKTs). GKT records of 40 innocent and 40 guilty Ss, for whom actual truth was established by confession, were assessed for their accuracy. When a predefined decision rule was used and inconclusive decisions were excluded, 97.4% of the innocent Ss and 53.3% of the guilty Ss were correctly classified with the SRR measure. For the RLL measure, the respective results were 97.2% and 53.1%. The combination of both measures improved detection of guilty Ss to 75.8% and decreased detection of innocent Ss to 94.1%. The combined measure seems to be a more useful means of identifying guilty suspects than each physiological measure alone. The results elaborate and extend those obtained in a previous field study (E. Elaad, 1990). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection of guilty knowledge in real-life criminal investigations.

The present study provides a first attempt to estimate the validity of the Guilty Knowledge Test (GKT) in real-life criminal investigations. Skin resistance responses in GKT records of 50 innocent and 48 guilty Ss, for whom actual truth was established by confession, were analyzed by two methods. On the basis of an a priori decision rule, 98% of the innocent and 42% of the guilty Ss were correctly classified. Signal detection measures based on various possible decision rules indicated that the distribution of guilty Ss was highly differentiated from the distribution of innocent Ss. An optimal decision rule yielded correct classifications for 94% of the innocent Ss and 65% of the guilty Ss. These results suggest that the GKT could be a useful investigative tool that protects innocent suspects from being falsely classified as guilty. The false-negative identifications were accounted for in terms of the realistic conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Leakage of relevant information to innocent examinees in the GKT: An attempt to reduce false-positive outcomes by introducing target stimuli.

This study focused on the Guilty Knowledge Test (GKT)—a psychophysiological detection method based on a series of multiple-choice questions, each having one relevant and several neutral (control) alternatives. The study examined a new method designed to reduce false-positive outcomes due to leakage of relevant items to innocent suspects by introducing target items (i.e., items known to all examinees but unrelated to the crime) to which participants have to respond (e.g., by pressing a key) while answering the GKT questions. Informed innocent participants showed relatively larger electrodermal responses to the critical items than uninformed participants, but not as large as the responses made by guilty participants. No differences between informed and uninformed innocent participants were obtained with a respiration measure. The use of the target items tended to reduce the differences between informed and uninformed innocent participants. The results further demonstrated that electrodermal responding to the relevant items was correlated with memory of these items. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of questions' repetition and variation on the efficiency of the Guilty Knowledge Test: A reexamination.

The effect of question repetition and variation on the efficiency of the Guilty Knowledge Test (GKT), based on electrodermal and respiration measures, was examined in a between-subjects experiment with 3 conditions. Each participant was presented with a sequence of 12 biographical questions. In Condition 1, a single question was repeated 12 times; in Condition 4, each of 4 different questions was repeated 3 times; and in Condition 12, 12 different questions were used. A monotonic relationship between the number of different questions used and detection efficiency was observed only with the electrodermal measure (the areas under the receiver operating characteristic curves, obtained with this measure in Conditions 1, 4, and 12 were .68, .81, and .99, respectively). These results demonstrate that a GKT based on multiple questions is superior to the use of many repetitions of a single or a few questions, and it can reach an almost perfect detection efficiency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)