History of the polygraphy, an instrument for the detection of deception.
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Finger pulse waveform length in the detection of concealed information.
An attempt was made to assess the efficiency of the finger pulse waveform length (FPWL), in detection of concealed information. For this purpose, two mock-theft experiments were designed. In the first, 40 guilty participants were examined while electrodermal, respiration and finger pulse volume were recorded. Results showed that detection accuracy with the FPWL was at least as good as the accuracy obtained with the other two measures (respiration changes and skin conductance responses). Detection efficiency was further improved when a combination of FPWL with the other two measures was used. In the second experiment, 39 guilty and 23 innocent participants were instructed to deny knowledge while the transducers were not attached to them. Then, the same questions were repeated while electrodermal, respiration and finger pulse volume were recorded. Results showed reduced rates of identification compared to the first experiment, which were explained by habituation. However, finger pulse was less affected by habituation than both respiration and skin conductance. Results suggested that the FPWL might be a useful addition to the existing measures in the detection of concealed information.
Adult↗
The roles of deception, intention to deceive, and motivation to avoid detection in the psychophysiological detection of guilty knowledge.
The present study focused on electrodermal differentiation between relevant and neutral items in the Guilty Knowledge paradigm. Three factors were varied in a between-subjects design. The role of deception was examined by varying the type of verbal answer to the questions ("yes," "no," and remaining silent). The intention to deceive factor was examined by contrasting subjects told to delay their answer ("yes" or "no") with those told to produce their answer immediately. Finally, motivation to avoid detection was manipulated by having half the subjects monetarily rewarded for an important (ego relevant) detection task (high motivation), whereas the remaining subjects were neither rewarded nor told that the task was important. The results indicated that a deceptive answer ("no") to the relevant question was associated with an increased differential skin conductance responsivity, but better than chance detection rates were obtained with truthful ("yes") and silent conditions. Equal and significant detection rates were observed when the responses were computed immediately following question presentation, whether the subjects had answered immediately or had delayed their answers. In contrast, differential electrodermal responsivity to the delayed answers was markedly attenuated. The motivation factor had no main or interactive effects on differential responsivity. The present results, together with those obtained in previous studies, suggest that whereas deception is neither a necessary nor a sufficient condition for psychophysiological detection, it may facilitate detection. Possible mechanisms through which such a facilitation could occur were considered.
Adult↗
Alcohol and the physiological detection of deception: arousal and memory influences.
Eighty male volunteers participated in an analogue study of the effects of alcohol intoxication at the time of a crime on the physiological detection of deception using control question and guilty knowledge techniques. Sixty-four of the subjects committed a mock crime and half of these were intoxicated during the crime. Sixteen subjects committed no crime and served as innocent controls. We found that intoxication at the time of the crime had no significant effect on polygraph test outcomes, although it did affect anticipatory arousal before the crime and subsequent memory for crime details. Manipulations designed to influence memory for crime details and arousal during the crime had differential effects for the two polygraph tests. On the guilty knowledge test, primed subjects who rehearsed specific details following the crime were more detectable than unprimed subjects. On the control question test, primed subjects were also more detectable, but only when arousal during the crime was high.
Adult↗
Meprobamate reduces accuracy of physiological detection of deception.
Normal male subjects attempted to deceive an experimenter recording electrodermal, respiratory, an cardiovascular activity. Those who had ingested a placebo or nothing were detected with statistically significant frequency on the basis of their phasic electrodermal responses, which clearly distinguished them from truthful suspects. That was not the case with deceptive subjects who had ingested 400 milligrams of meprobamate, nor did the examiner detect which subjects had received the drug.
Blood Pressure↗
The origin of conditional logic: does a cheater detection module exist?
The domain-specific hypothesis of L. Cosmides (1989) and L. Cosmides and J. Tooby (1989, 1992) positing that conditional logic has its origin in the evolution of social exchange and in the detection of potential cheaters was tested against a more domain-general hypothesis positing that adult reasoning is logical and that errors in conditional reasoning arise from misunderstandings, not from a lack of logicality. The results of 5 experiments with undergraduate students (n = 682 for Experiments 1-4; n = 188 for Experiment 5), which involved a series of selection tasks that yielded specific predictions about participant performance, were not consistent with the cheater detection hypothesis. Findings supported the misunderstandings hypothesis and imply that adults possess general-purpose logical competence versus domain-specific modules.
Adult↗
Psychophysiological and vocal measures in the detection of guilty knowledge.
The Guilty Knowledge Test (GKT) and its variant, the Guilty Actions Test (GAT), are both psychophysiological questioning techniques aiming to detect guilty knowledge of suspects or witnesses in criminal and forensic cases. Using a GAT, this study examined the validity of various physiological and vocal measures for the identification of guilty and innocent participants in a mock crime paradigm. Electrodermal, respiratory, and cardiovascular measures successfully differentiated between the two groups. A logistic regression model based on these variables achieved hit rates of above 90%. In contrast to these results, the vocal measures provided by the computerized voice stress analysis system TrusterPro were shown to be invalid for the detection of guilty knowledge.
Adult↗
Determination of benomyl, carbendazim and 2-aminobenzimidazole (2-ab) in plant materials. Part I: Apples, red-currants, grapes, kale and sugar beets.
Benomyl and Carbendazim are widely used fungicides with systemic activity. In the Federal Republic of Germany the legal limits of Benomyl and Carbendazim lie between 0.1 and 7 ppm dependent on the substrate. A method for the determination of Benomyl and Carbendazim in apples, red-currants, grapes, kale, and sugar beets was developed. Benomyl and Carbendazim are extracted with ethyl acetate, saponified and determined as 2-aminobenzimidazole by thin-layer chromatography. The detection limits lie between 0.02--0.08 ppm, recoveries amount to 87% at 0.5-ppm levels.
Benomyl↗
[Usefulness of the repeated presentation of questions on the psychophysiological detection of deception].
Two experiments were conducted to assess the usefulness of repeated questioning for the psychophysiological detection of deception. Twenty-four female subjects were instructed to conceal the critical item which they had previously selected, and their skin conductance response (SCR) was simultaneously recorded. In Experiment 1, the amplitudes of SCR to both critical and noncritical items tended to decrease. However, responses to the critical item was consistently larger than that to other noncritical ones during the total of nine presentations in this series where the critical item was pseudo-randomly inserted among the four non-critical items. In Experiment 2, the difference of SCR to the critical and noncritical items was enhanced compared with Experiment 1 at the first exposure in three successive presentations, though this difference was diminished at the following 2nd and 3rd presentations. These results suggest that the successive presentations of stimulus under the detection of deception would be effective to discriminate the responses to critical item from noncritical items, and they are discussed in terms of stimulus significance.
Adult↗
A comparison of methods for ERP assessment in a P300-based GKT.
P300-based GKT (guilty knowledge test) has been suggested as an alternative approach for conventional polygraphy. The purpose of this study is to evaluate three classifying methods for this approach and compare their performances in a lab analogue. Several subjects went through the designed GKT paradigm and their respective brain signals were recorded. For the analysis of signals, BAD (bootstrapped amplitude difference) and BCD (bootstrapped correlation difference) methods as two predefined methods alongside a new approach consisting of wavelet features and a statistical classifier were implemented. The rates of correct detection in guilty and innocent subjects were 74-80%. The results indicate the potential of P300-based GKT for detecting concealed information, although further research is required to increase its accuracy and precision and evaluating its vulnerability to countermeasures.
Electroencephalography↗
The comparison question test: does it work and if so how?
In a mock crime study of the comparison question test (CQT), 35 subjects decided to participate as guilty and 30 as innocent. Two conditions were varied: Explaining the comparison questions in the pretest interview and re-discussing comparison questions between charts. Higher identification rates (approximately 90% for guilty and innocent participants) were achieved in groups with explanation of comparison questions than in groups without explanation. Re-discussing comparison questions had no effect on identification rates. Ratings of subjective stress due to relevant and comparison questions were also obtained and can be seen as indicators of the significance of the questions. The significance of comparison questions was hardly affected by the different testing conditions. When effects are detectable at all, they contradict theoretical expectations in their direction. Results are discussed in terms of the significance of comparison questions used in polygraph testing.
Adult↗
Detecting deception in facial expressions of pain: accuracy and training.
Clinicians tend to assign greater weight to nonverbal expression than to patient self-report when judging the location and severity of pain. However, patients can be successful at dissimulating facial expressions of pain, as posed expressions resemble genuine expressions in the frequency and intensity of pain-related facial actions. The present research examined individual differences in the ability to discriminate genuine and deceptive facial pain displays and whether different models of training in cues to deception would improve detection skills. Judges (60 male, 60 female) were randomly assigned to 1 of 4 experimental groups: 1) control; 2) corrective feedback; 3) deception training; and 4) deception training plus feedback. Judges were shown 4 videotaped facial expressions for each chronic pain patient: neutral expressions, genuine pain instigated by physiotherapy range of motion assessment, masked pain, and faked pain. For each condition, the participants rated pain intensity and unpleasantness, decided which category each of the 4 video clips represented, and described cues they used to arrive at decisions. There were significant individual differences in accuracy, with females more accurate than males, but accuracy was unrelated to past pain experience, empathy, or the number or type of facial cues used. Immediate corrective feedback led to significant improvements in participants' detection accuracy, whereas there was no support for the use of an information-based training program.
Adolescent↗
Simple, effective countermeasures to P300-based tests of detection of concealed information.
We found countermeasures to protocols using P300 in concealed information tests. One, the "six-probe" protocol, in Experiment 1, uses six different crime details in one run. The countermeasure: generate covert responses to irrelevant stimuli for each probe category. Hit rates were 82% in the guilty group; 18% in the countermeasure group. The average reaction time (RT) distinguished these two groups, but with overlap in RT distributions. The "one-probe" protocol, in the second experiment, uses one crime detail as a probe. Here, one group was run in 3 weeks as a guilty group, a countermeasure group, and again as in Week 1. COUNTERMEASURE: Covert responses to irrelevant stimuli. In Week 1, hit rate was 92%. In Week 2, it was 50%. In Week 3, 58%. There was no overlap in the irrelevant RT distribution in Week 2: Countermeasure use was detectable. However, in Week 3, the RT distributions resembled those of Week 1; test-beaters could not be caught. These studies have shown that tests of deception detection based on P300 amplitude as a recognition index may be readily defeated with simple countermeasures that can be easily learned.
Adult↗
Current evidence for the existence of laryngeal macrotremor and microtremor.
To test for the existence of laryngeal "microtremors" two experiments were conducted on humans. The first analyzed the acoustic characteristics of observable tremors (macrotremors) in the voice of singers using vocal vibrato and in pathologic subjects producing vocal tremor. In both of these groups acoustic oscillations between 4 and 8 Hz were found. The second study, using a normal subject, sampled electromyographic (EMG) activity from laryngeal and arm muscles during isometric contraction to determine if a periodic component (microtremor) was present in either muscle's contraction pattern. A 9-Hz signal was detected in limb muscle contraction, whereas no periodicity was found in signals from laryngeal muscles. The application of these findings to the theory behind voice "stress" analyzers is discussed
Female↗
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.
Adult↗
Psychophysiological detection through the guilty knowledge technique: effects of mental countermeasures.
The effects of mental countermeasures on the efficiency of psychophysiological detection with the Guilty Knowledge Technique were examined in a mock-crime experiment with 4 groups of participants: innocent participants who were not involved in the mock crime, guilty controls who committed the mock crime but received no countermeasure instructions, and guilty participants who received countermeasure instructions, and guilty participants who received countermeasure instructions and were allowed to practice the countermeasures. The countermeasure instructions encouraged participants to recall emotional situations from their past and imagine themselves in these situations during presentation of irrelevant questions. Results revealed a significant reduction in electrodermal detection efficiency under the 2 countermeasure conditions with no differences between them. No countermeasures effects were observed with the respiration line length measure.
Adult↗
Ambulatory system for the quantitative and qualitative analysis of gait and posture in chronic pain patients treated with spinal cord stimulation.
The physical activity in normal daily life is determined to a large extent by the functional ability of a subject. As a result, the measurement of the physical activity that a subject performs spontaneously could be a useful and objective measurement of disability, particularly in patients with disease-related functional impairment. The aim of this study is to provide an accurate method for the measurement and analysis of the physical activity under normal life conditions. Using three kinematical sensors strapped to the body, both the posture and the gait parameters can be assessed qualitatively and quantitatively. A detailed description of the algorithms used to analyse both the posture and the gait are presented in this paper. Two methods, based on different sensor configurations and signal processing, are proposed for the detection of sitting and standing postures (Methods P1 and P2). Two other methods are used for the quantitative assessment of walking (Methods W1 and W2). The performance of the algorithms (expressed in terms of sensitivity, specificity and error) is based on the comparison of data recorded simultaneously by a non-interfering observer (reference data) with the data provided by the recording system (21 patients, 61 h). Sensitivity and specificity are respectively 98.2% and 98.8% (P1), 97.8% and 98.1% (P2) for sitting; 98.0% and 98.5% (P1), 97.4% and 97.8% (P2) for standing; 97.1% and 97.9% (W1), 92.4% and 94.9% (W2) for walking; and finally, 99.2% and 98.6% for lying. Overall detection errors (as a percent of range) are as follows: 1.15% (P1) and 1.20% (P2) for sitting, 1.36% (P1) and 1.40% (P2) for standing, 1.20% (W1) and 1.60% (W2) for walking and 0.40% for lying. The error for the estimated walking distance and the speed is 6.8% and 9.6%, respectively. We conclude that both methods can be used for the accurate measurement of the basic physical activity in normal daily life. Measurements performed before and after the delivery of a treatment can therefore provide information of unprecedented accuracy and objectivity on the ability of a procedure, in this case spinal cord stimulation, to restore functional capabilities.
Adult↗
Cross-modal physiological effects of electrodermal lability in the detection of deception.
This study examined the effects of individual differences in electrodermal lability on cardiovascular, respiratory, and electrodermal responses (EDRs) in the detection of deception. One Day 1 each of 74 subjects rested quietly for 3 min. while skin conductance was recorded. Electrodermal lability was scored for each subject, those giving frequent nonspecific EDRs being labiles and those giving few being stabiles. On Day 2, usually 1 week later, 40 of the subjects attempted to deceive a professional polygraph examiner in a field-type test. The 34 remaining subjects attempted to convince the examiner, who was blind as to each subject's condition, that they were indeed being truthful. Deception by stabile subjects was detected less frequently than was deception by labile subjects. Among truthful subjects, the more labile were falsely detected as deceptive on more questions than were their stabile counterparts. Although accuracy of detection was greatest with the EDR, the effects of lability on detection were similar for electrodermal, cardiovascular, and respiratory measures. Labiles also had a higher heart rate during the polygraph test than did stabiles.
Adolescent↗