Biomedical subjects

Gershon Ben-Shakhar

Publications and source records attributed to Gershon Ben-Shakhar.

9 recordsLinked to original sources

PubMed2006

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↗

PubMed2006

The effect of novel distractors on performance in focused attention tasks: a cognitive-psychophysiological approach.

In the present study, we examined whether or not novel stimuli affect performance in a focused attention task. Participants responded to a central target while an irrelevant distractor in the visual display was occasionally changed. In Experiment 1, both target and distractor were presented centrally within the focus of attention. In Experiment 2, a central target was presented along with an irrelevant distractor at a peripheral location, outside the focus of attention. Novel distractors were associated with longer latencies and enhanced orienting responses (as measured by skin conductance responses) only when presented at an attended location. In contrast, as is demonstrated in Experiment 3, the same peripheral novel distractors interfered with task performance when they possessed task-relevant information. These results indicate that there is a fundamental difference between novel stimuli and task-relevant stimuli. Whereas the former exert influence only within the focus of attention, the latter affect performance even when positioned in an unattended location. Our findings have important implications for the operation of visual attention.

Attention↗

PubMed2005

Behavioral and physiological measures in the detection of concealed information.

The authors examined the incremental validity of the reaction time (RT) measure beyond that of skin conductance response (SCR) in the detection of concealed information. Participants performed a Stroop-like task in which they named the color of critical and neutral words. Results show that the SCR highly differentiated between the relevant and neutral words. However, the RT demonstrated a significant differentiation only when the critical words denoted personally significant items (e.g., one's own name) and not when they denoted crime-relevant items related to a simulated crime. In both cases, combining the 2 measures yielded no advantage over the use of SCR alone. Thus, although behavioral measures may differentiate between relevant and neutral information in some cases, their practical use is questionable.

Adult↗

PubMed2003

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 overall 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.

Adult↗

PubMed2003

Dissociations of personally significant and task-relevant distractors inside and outside the focus of attention: a combined behavioral and psychophysiological study.

Studies of attentional capture by personally significant stimuli have reached inconsistent results, possibly because of improper control of the participants' attention. In the present study, the authors controlled visual attention by using a Stroop-like task. Participants responded to a central color and ignored a word presented either centrally (i.e., at the focus of attention) or peripherally (i.e., outside the focus of attention). Central words led to slower reaction times and larger orienting responses for significant items than for neutral items. These effects largely disappeared when the words appeared in a peripheral location. The peripheral words interfered with performance when they were relevant to task demands. These results indicate that there is a fundamental difference between task-relevant words and personally significant words: The former capture attention even when presented peripherally, whereas the latter do not.

Attention↗

PubMed2003

Estimating the validity of the guilty knowledge test from simulated experiments: the external validity of mock crime studies.

This experiment was designed to examine the external validity of the standard mock-crime procedure used extensively to evaluate the validity of polygraph tests. The authors manipulated the type of mock-crime procedure (standard vs. a more realistic version) and the time of test (immediate vs. delayed) and examined their effects on the validity of the Guilty Knowledge Test (GKT) and the recall rate of the relevant items. The results indicated that only the type of mock-crime affected the 2 outcome variables. The realistic procedure was associated with a lower recall rate and weaker detection efficiency than the standard procedure. However, these effects were mediated by the type of GKT questions used. Practical implications of these results are discussed.

Adult↗

PubMed2003

The effects of serial position and frequency of presentation of common stimulus features on orienting response reinstatement.

Two factors that might affect the novelty value of a test stimulus (the frequency of appearance of features common to the test stimulus and the set of preceding stimuli, and the serial position of these features) were systematically manipulated, and their effects on the electrodermal component of the orienting response (OR) were examined. We presented 256 participants with both verbal and pictorial stimulus sequences. Following 12 presentations of control stimuli, a test stimulus, which shared two common components with some of the control stimuli, was presented, followed by two additional presentations of control stimuli. The results revealed that recent presentations of the common components significantly reduced OR magnitude to the test stimulus, whereas the presentation frequency of common components had no significant effect. The implications of these findings for the feature-matching theory are discussed and a modification of the theory is proposed.

Acoustic Stimulation↗

PubMed2002

Trial by polygraph: reconsidering the use of the guilty knowledge technique in court.

Polygraph test results are by and large ruled inadmissible evidence in criminal courts in the US, Canada, and Israel. This is well-conceived with regard to the dominant technique of polygraph interrogation, known as the Control Question Technique (CQT), because it indeed does not meet the required standards for admissible scientific evidence. However, a lesser known and rarely practiced technique, known as the Guilty Knowledge Test (GKT), is capable, if carefully administered, of meeting the recently set Daubert criteria. This paper describes the technique, and argues for considering its admissibility as evidence in criminal courts.

Canada↗

PubMed2002

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.

Adult↗