Eitan Elaad

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.

Effects of mental countermeasures on psychophysiological detection in the guilty knowledge test

This study focused on the effects of mental countermeasures on psychophysiological detection in a guilty knowledge paradigm. Two experiments which utilized a 3 x 2 between subjects factorial design were conducted. Two types of mental countermeasures (specific dissociations from the relevant stimulus and continuous dissociation throughout the entire test, as well as a control-no countermeasure condition were used). Each group was further subdivided into two conditions--a high attention condition created by motivational instructions and a deceptive verbal response to the relevant question; and a low attention condition in which no motivational instructions were provided and no verbal response was required. The results of both experiments (one was conducted in a field set up, and the other utilized more standard experimental equipment and measurement procedures) revealed the following pattern: the item-specific countermeasures tended to increase psychophysiological detection, whereas the continuous dissociations tended to decrease detection efficiencies. The pattern was consistent across attention conditions and experiments but it was stronger in the field experiment where overall detection efficiency was relatively high. In other respects the present results replicated previous findings and revealed a significant effect for the attention factor.

Effects of context and state of guilt on the detection of concealed crime information

The effects of the state of guilt and the context in which critical information was received on the accuracy of the Concealed Information Test (CIT) were examined in a between-subjects mock crime experiment. 100 participants were randomly assigned to four experimental conditions and one control condition. The experimental conditions were created using a 2 x 2 factorial design (two conditions of the context in which the crime-related details were collected - crime context or neutral context, crossed with two guilt conditions - accomplices or innocents). Results indicated that accomplices were more effectively detected than innocent participants, although both were given the same critical information. Information gathered in the crime context yielded stronger orientation to the critical items than similar information gathered in a neutral context.

The Challenge of the Concealed Knowledge Polygraph Test

This paper introduces the concealed knowledge polygraph test (CKT) and suggests that it might be useful for the criminal justice system. The main point is that the CKT is a standard and objective psychological test that can to some extent protect the innocent from false allegation. A review of 15 mock crime studies of the CKT supports this contention. It revealed average detection rates of 80.6% for guilty examinees and 95.9% for the innocent. Furthermore, in 11 of these studies no false positive identifications (i.e. failures to exonerate innocent suspects) were observed. Two field studies revealed similar results, with false-positive error rates that are not larger than expected by chance. However, in the field studies, the detection rates for guilty suspects were substantially lower than those obtained in the 15 experimental studies. Suggestions for enhancing the detection rate of guilty suspects in real life settings are provided.Finally, the effects of several possible countermeasures, such as the use of drugs, biofeedback training and behavioural countermeasure maneouvres, are discussed. It seems that drugs and biofeedback are not effective in the CKT. However, at least the electrodermal measure is vulnerable to the effects of behavioural countermeasures. Possible ways to deal with the problem are discussed.

Countering Countermeasures in the Concealed Information Test Using Covert Respiration Measures

The effects of physical and mental countermeasures on the accuracy of the concealed information test (CIT) were examined in a mock crime experiment with 64 participants. To combat countermeasures, two covert respiration measures, hidden in the seat and back of the examination chair, were used in addition to the standard physiological measures (SCR, FPWL, RLL). Some guilty participants were trained to use either physical or mental countermeasures and apply them to distort the outcomes of the CIT. In the second phase of the experiment participants were detached from the standard polygraph devices and examined solely with the two covert measures. Results indicated that physical countermeasures lowered SCR accuracy but had a relatively small effect on the other standard measures. On the other hand, SCR was relatively resistant to mental countermeasures. Both covert measures were resistant to physical countermeasures in the polygraph phase. When the standard devices were removed, the covert seat measure was effective in the no countermeasure and in the mental countermeasure conditions but not when physical countermeasures were applied. The back measure was entirely ineffective.

Effects of coping and cooperative instructions on guilty and informed innocents' physiological responses to concealed information.

Previous research on the Concealed Information Test indicates that knowledge of the critical information of a given event is sufficient for the elicitation of strong physiological reactions, thus facilitating detection by the test. Other factors that affect the tests efficacy are deceptive verbal responses to the tests questions and motivation of guilty examinees to avoid detection. In the present study effects of coping and cooperative instructions - delivered to guilty and innocent participants - on detection were examined. In a mock-theft experiment guilty participants who actually committed a mock-crime, and informed innocent participants who handled the critical items of the crime in an innocent context, were instructed to adopt either a coping or a cooperative attitude toward the polygraph test. Results indicated that both, guilt and coping behavior, were associated with enhanced physiological responses to the critical information, whereas innocence and cooperative behavior attenuated physiological responses. Theoretical and applied implications of the results are discussed.

Lie-detection biases among male police interrogators, prisoners, and laypersons.

Beliefs of 28 male police interrogators, 30 male prisoners, and 30 male laypersons about their skill in detecting lies and truths told by others, and in telling lies and truths convincingly themselves, were compared. As predicted, police interrogators overestimated their lie-detection skills. In fact, they were affected by stereotypical beliefs about verbal and nonverbal cues to deception. Prisoners were similarly affected by stereotypical misconceptions about deceptive behaviors but were able to identify that lying is related to pupil dilation. They assessed their lie-detection skill as similar to that of laypersons, but less than that of police interrogators. In contrast to interrogators, prisoners tended to rate lower their lie-telling skill than did the other groups. Results were explained in terms of anchoring and self-assessment bias. Practical aspects of the results for criminal interrogation were discussed.

Effects of goal- and task-oriented motivation in the guilty action test.

The present study examined the effectiveness of the Guilty Action Test in detecting critical information from goal-oriented and task-oriented informed innocent examinees. A mock crime procedure was employed and informed innocent participants were either motivated to prove innocence (goal-oriented motivation) or to prove innocence by being cooperative on the test (task-oriented motivation). Half of the participants in each motivation condition were promised course credit reward for successful completion of their mission to prove innocence or to be cooperative (high incentive level). The other half were promised no reward (low incentive level). A fifth group of uninformed innocent participants served for control purposes. Electrodemal, respiration, and cardiovascular measures were used to indicate the motivation effects. Results showed that the combination of goal-oriented instructions and an incentive for success contributed to enhanced responses to the crime-related information. The combination of task-oriented instructions and an incentive for success attenuated these responses. Skin conductance responses were most sensitive to these effects. Theoretical and practical aspects of the results were discussed.

Effects of incomplete information on the detection of concealed crime details.

The accuracy of the Concealed Information Test in correct classification of informed guilty and informed innocent participants was assessed when the explicitness of the obtained information varied. For these purposes, a mock crime procedure was employed and participants were randomly assigned to six conditions formed by combinations of two levels of the state of guilt (guilty and innocent) and three levels of information completeness (exact, indicative, non-specific). As expected, informed guilty participants were more accurately detected than informed innocents. It was further found that when the gathered information was less explicit, detection efficiency decreased. Theoretical and practical implications of the present results are discussed.

The Accuracy of Human Decisions and Objective Measurements in Psychophysiological Detection of Knowledge

I examined the relative detection efficiency of three measurements--skin resistance response (SRR) amplitude, respiration line length (RLL), and human respiration response evaluation (RRE)--in a guilty knowledge experiment. Thirty-two subjects were presented with lists of personal information in which only one of five items was correct. Subjects were instructed to try to avoid detection of the relevant items in the polygraph test. All three measurements discriminated better than chance between relevant and neutral items, with the objectively measured SRR and RLL superior to the subjective RRE. When SRR and RLL were compared for their relative efficiency, the former yielded better detection. The differentiation was even better with a measure that combined the SRR and the RLL. The results are discussed with respect to previous findings and practical implications.