Mental and physical countermeasures reduce the accuracy of the concealed knowledge test

Abstract

The effects of a physical (pressing the toes to the floor) and a mental (counting backward by sevens) countermeasure on the concealed knowledge test (CKT) were examined in a mock crime experiment with 40 subjects. Some knowledgeable subjects were informed about the nature of the CKT and were trained in the use of a countermeasure, whereas others remained uninformed. All subjects were offered a monetary reward if they could produce a truthful outcome. Subjects were tested using standard field techniques and instrumentation. The physical and, to a lesser extent, the mental countermeasures reduced the accuracy of the CKT. These results clearly demonstrate that the CKT has no special immunity to the effects of countermeasures.

Countering Countermeasures in the Concealed Information Test Using Covert Respiration Measures

“…These countermeasures were selected because they proved to be effective in a previous study (Honts et al 1996). Participants in the physical countermeasure condition were asked to press their toes against the floor when the chosen neutral items were presented.…”

“…The experiment was conducted by two experimenters (one male and one female) and followed the countermeasures procedure used previously by Honts et al (1996) and the procedure used by Elaad and Ben-Shakhar (2008) for applying the covert respiration measures. Specifically, two respiratory effort transducers hidden in the seat and the back of a polygraph examination chair were used, along with standard respiration, electrodermal and cardiovascular measures, to detect guilty participants who tried to conceal information.…”

“…However, it was demonstrated that the CIT is vulnerable to physical countermeasures (e.g., pressing the toes against the floor when control items are presented) as well as mental countermeasures (e.g., counting numbers each time a control item appears). This vulnerability to countermeasures might increase false negative outcomes and impair the validity of the CIT (BenShakhar and Dolev 1996;Elaad and Ben-Shakhar 1991;Honts et al 1996).…”

Estimating the Validity of the Guilty Knowledge Test From Simulated Experiments: The External Validity of Mock Crime Studies.

“…Typically, they may be tested days, weeks, and sometimes months after the crime was committed (see Ben-Shakhar & Furedy, 1990, pp. 55-56). Although in some GKT studies, memory for the critical items was not verified (e.g., Honts, Devitt, Winbush, & Kircher, 1996;Iacono, Boisvenu, & Fleming, 1984), the typical GKT experiment differs from the realistic setup in which the GKT may be used in several important ways. In particular, factors affecting perception and memory that may be crucial for the efficiency of the GKT in applied settings do not play a sufficient role in mock-crime experiments.…”

The Deception Clues in Forensic Contexts: The Lie Detection Psychology

“…Some attempt to recreate the manual scoring process, an example being the Computerized Polygraph System. Its current algorithm is based on real criminal case data provided by US Secret Service [20] and only uses skin conductance amplitude, the amplitude of increase in the baseline of the cardiograph, and combined upper and lower respiration line length as data.…”