Biomedical subjects

G Ben-Shakhar

Publications and source records attributed to G Ben-Shakhar.

At least 19 recordsLinked to original sources

PubMed2000

Psychophysiologic assessment of aversive conditioning in posttraumatic stress disorder.

BACKGROUND: The objective of this study was to evaluate the acquisition, generalization, and extinction of conditioned physiologic responses to aversive stimuli in posttraumatic stress disorder (PTSD). METHODS: Thirty-six PTSD patients, 20 individuals with past trauma and no current PTSD, and 30 mentally healthy individuals without exposure to major trauma underwent a differential aversive conditioning experiment. Bursts of 105 dB white noise were used as unconditioned stimuli (UCSs), and 35x24 mm slides of different colors served as either CS+ (paired) or CS- (unpaired) stimuli. Heart rate (HR) and nondominant palm skin conductance (SC) were measured at rest and between 1 and 4 sec following each CS presentation. RESULTS: The PTSD group showed higher levels of resting SC and resting HR, larger SC responses to the initial presentation of unpaired CSs, larger HR responses following paired CS+ stimuli, larger SC responses to unpaired CS- during acquisition and extinction, and larger SC and HR responses to CS+ during extinction. The group differences in responses to CS+ during extinction remained statistically significant after controlling for age, resting physiologic levels, and initial responsivity. CONCLUSIONS: PTSD is associated with elevated autonomic responses to both innocuous and aversive stimuli, with larger responses to unpaired cues and with reduced extinction of conditioned responses.

Adult↗

PubMed2000

Orienting response reinstatement and dishabituation: effects of substituting, adding, and deleting components of nonsignificant stimuli.

The prediction that orienting response (OR) reinstatement is negatively related to the measure of common features, shared by the stimulus input and representations of preceding events, and positively related to the measure of their distinctive features, was examined. A nonsignificant test stimulus (TS) was presented after nine repetitions of a standard stimulus (SS), followed by two additional repetitions of SS. TS was created by either substituting 0, 1, or 2 components of SS (Experiment 1), or by either adding or deleting 0, 1, or 2 components of SS (Experiment 2). Skin conductance changes to TS (OR reinstatement) and the subsequent SS (dishabituation) were used as dependent measures. The results of Experiment 1 supported the prediction that substituting components of neutral stimuli affects OR reinstatement, with a larger effect for between-categories than within-categories substitution. Experiment 2 demonstrated that adding and deleting components similarly affects OR reinstatement.

Adult↗

PubMed1997

Effects of item repetitions and variations on the efficiency of the guilty knowledge test.

Two mock-crime experiments were designed to examine the effects of question repetition and variation on the efficiency of the guilty knowledge test. In the first experiment, two factors (single vs. multiple questions, and high vs. low motivation) were manipulated and in the second experiment, which was an analog study conducted in a police laboratory using field equipment, only the first factor was examined. Similar detection efficiencies were obtained in both experiments when a single question was repeated 12 times, and when each of four different questions was repeated 3 times. The results also showed that accumulating information across repetitions and across physiological measures tended to increase detection efficiency and reduce false positive errors. The results of Experiment 1 suggest that motivation to avoid detection may be associated with better detection efficiency.

Adult↗

PubMed1996

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↗

PubMed1996

Stimulus novelty and significance in electrodermal orienting responses: the effects of adding versus deleting stimulus components.

Several aspects of a feature-matching theory formulated to account for the roles of stimulus novelty and significance in determining orienting responses (ORs) were examined. Stimulus significance and stimulus novelty were independently manipulated, and the electrodermal component of the OR was measured while sequences of compound pictorial or verbal stimuli were presented. Each sequence included a test stimulus, which was either significant or neutral, and was preceded by several standard control stimuli. Novelty was manipulated by either adding or deleting components from the standard stimuli, and significance was defined within the framework of the guilty knowledge paradigm. A change in the number of components of both verbal and pictorial test stimuli affected OR magnitude for significant but not for neutral test stimuli. Similar ORs were obtained regardless of the direction of stimulus change.

Acoustic Stimulation↗

PubMed1996

Is an apple a fruit? Semantic relatedness as reflected by psychophysiological responsivity.

In the present study, we investigated orienting response generalization across various types of semantically related stimuli. Four experiments, based on a modified version of the guilty knowledge technique, were designed to examine whether semantic relations based on abstract features are reflected by electrodermal responsivity. No generalization across coordinates was obtained, but a moderate degree of generalization was demonstrated between a word and its superordinate category (e.g., table-furniture) and between a word and its synonym. Complete generalization occurred from a verbal label of an object to its pictorial representation, and vice versa. These results are compatible with our proposal that partial identification of the test stimulus as relevant is a necessary condition for generalization in the guilty knowledge technique.

Adult↗

PubMed1995

A randomized controlled outcome and follow-up study of Mann's time-limited psychotherapy.

Thirty-three patients were assessed for suitability for time-limited psychotherapy (TLP). A battery of outcome measures was composed of patient self-report measurements and objective judgments by external ("masked") raters. Patients were randomly assigned to either the experimental group, which received TLP immediately, or the control group, whose TLP was delayed for 3 months. Patients were evaluated on outcome measures at TLP termination and again at 6 and 12 months after termination. Significant improvement was observed in the experimental group after TLP, but the control patients did not show any systemic changes after waiting. However, after TLP, the control patients improved significantly. The average effect size measured by the differences between gain scores of the experimental patients (before vs. after treatment) and those of the control patients (before vs. after waiting) was 0.986 SD. The gains achieved after therapy were stable in both groups after 6- and 12-month follow-ups.

Adult↗

PubMed1995

Generalization of the orienting response to significant stimuli: the roles of common and distinctive stimulus components.

This study focused on the effects of common and distinctive stimulus components on the generalization of the orienting response (OR) to significant stimuli. Compound pictorial stimuli were used as the relevant items memorized by the subjects. Skin conductance responses were measured during the subsequent presentation of a stimulus sequence that included a test stimulus that shared some common components with the relevant one. The two types of stimulus components (common and distinctive) were independently manipulated. As predicted by the feature-matching theory, both types of features affected OR generalization, but the distinctive components effect was due mainly to a large decline in OR with the introduction of the first distinctive component. As hypothesized, no interaction was observed between the effects of common and distinctive components. Contrary to expectations, similar OR generalization was obtained regardless of whether the test stimulus was constructed by deleting stimulus components from the relevant stimulus or by adding components to that stimulus.

Adult↗

PubMed1995

Demandingness and belligerence in hospitalized depressed Holocaust concentration camp survivors as perceived by the staff.

Twelve staff members, blind to the hypotheses, rated depressed, hospitalized concentration camp survivors, 40 years after their liberation, as more demanding, belligerent and irritating in their behavior towards staff in comparison with their matched counterparts. Survivors' behavior was discussed in terms of reenactment of traumatic scenes from their past. Staff shows consistent although not significant tendencies to dislike the survivors. Theoretical and clinical implications were drawn.

Concentration Camps↗

PubMed1994

Electrodermal differentiation of deception: the effect of choice versus no choice of deceptive items.

In the differentiation-of-deception paradigm (DDP), the experimental and control conditions, respectively, consist of questions answered deceptively (D) and honestly (H). Previous DDP studies with the electrodermal SCR as the dependent variable have yielded the basic increase in responding to D relative to H questions (D > H), and have indicated that this effect is probably not due to cognitive factors such as differential retrieval difficulty, and is also relatively unaffected by motivational factors. To test the notion that the D > H effect does not represent genuine deception because of the elimination of the element of choice in the DDP, the present study varied, between two groups of 16 subjects, the degree to which subjects could choose which questions they would answer deceptively. If choice were necessary, or even important, for the differentiation-of-deception phenomenon, the D > H effect should have been greater in the free-choice condition, but the (nonsignificant) trend was in a direction opposite to this prediction. Another orthogonally-varied, between-subject manipulation, was the relative frequency of D and H items. The basic electrodermal D > H phenomenon, including the curious lack of response habituation during the session, has now been duplicated over a variety of conditions, but the mechanisms underlying the phenomenon are far from being well understood.

Adolescent↗

PubMed1994

The roles of stimulus novelty and significance in determining the electrodermal orienting response: interactive versus additive approaches.

Two competing approaches for the roles of stimulus significance and novelty in determining orienting responses (ORs) were tested and compared. According to the first, ORs to significant stimuli are determined by sets and expectations and are relatively independent of the contrast between the test stimulus and preceding stimuli, whereas responses to nonsignificant test stimuli are products of a Sokolovian match/mismatch process. According to an alternative approach, novelty and significance contribute independently and additively to the OR. Stimulus significance and novelty were independently manipulated in two experiments, and the electrodermal component of the OR was measured while sequences comprising compound pictorial or verbal stimuli were presented. Each sequence included a test stimulus that was either significant or neutral and was preceded by several control stimuli. Novelty was manipulated by varying the contrast between the test and the control stimuli. The results revealing no interaction between stimulus significance and novelty were interpreted as supporting the theory proposed by Cati and Ben-Shakhar (1990).

Acoustic Stimulation↗

PubMed1992

The effect of common versus distinctive stimulus features on electrodermal orientation to significant stimuli.

The relationship between electrodermal responsivity and stimulus similarity was previously demonstrated in a series of studies. These studies were guided by a feature-matching model according to which similarity is an additive function of the common and distinctive features of the stimuli. In these experiments common and distinctive features were simultaneously manipulated, thus confounding the effects of the two sets of features. In the present experiment, we examined the separate effects of these two sets of features by an independent manipulation of common and distinctive components of the stimuli. A modified version of the guilty knowledge technique was employed, with compound pictorial and verbal stimuli (schematic faces and verbal descriptions of people) as the relevant items memorized by the subjects. Skin conductance responses were measured during the subsequent presentation of a stimulus sequence comprised of a test stimulus, which shared some common components with the relevant stimulus, and several neutral control stimuli. As hypothesized, a larger number of distinctive components resulted in decreased responsivity. Yet, contrary to our expectation, the number of common components of the relevant and test stimuli had no effect on responsivity. Several hypotheses are suggested to account for this unexpected result.

Adult↗

PubMed1991

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↗

PubMed1991

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↗

PubMed1990

Novelty and significance in orientation and habituation: a feature-matching approach.

A feature-matching model to account for the effects of novelty and significance on psychophysiological responsivity is presented. 2 experiments based on a modified version of the Guilty Knowledge Technique were designed to test predictions derived from the proposed model. Results of Experiment 1 demonstrated that electrodermal responsivity to the test stimulus reflected the degree to which the subjects were habituated to its components. Experiment 2 provided additional support for the proposed model and suggested that the effects of novelty and significance were additive. These findings support the hypothesis that responsivity is positively related to the degree of match between the input and the representation of significance, and it is negatively related to the similarity between the input and the preceding stimuli. It is argued that the proposed model clarifies the processes involved in orienting response elicitation.

Arousal↗

PubMed1989

Effects of motivation and verbal-response type on psychophysiological detection of information.

Two independent experiments were designed to investigate the effects of motivation to deceive and the type of verbal response on psychophysiological detection using the Guilty Knowledge Technique. The first was a field experiment in which 72 subjects were randomly assigned to 8 experimental conditions. These conditions were created by a 2 x 4 factorial design (two motivational states crossed with four verbal response modes--affirming, denying, repeating, or no verbal response to questions about personal information). The second experiment was a laboratory experiment in which 160 students were assigned to the same 8 conditions. Results of both experiments indicated that highly motivated subjects were detected better than less motivated subjects. The act of lying was associated with enhanced differential responsivity, but no effects were obtained for verbal response versus no response or for variable versus standard verbal response. Differential responsivity tended to decline when questions were repeated. The first experiment revealed a clear advantage of electrodermal measures over respiration and cardiovascular measures. The results were discussed in relation to previous findings, a new theoretical formulation, and practical implications.

Adult↗

PubMed1989

Stimulus novelty and significance as determinants of electrodermal responsivity: the serial position effect.

Three experiments examined the effects of stimulus novelty and significance on the skin conductance component of the orienting response. The test stimuli used in the different experiments involved either a neutral change in stimulation (i.e., adding or deleting components to the standard stimuli), or an introduction of a significant element to the standard stimulus. The serial position of the test stimulus was manipulated in all three experiments. In Experiment 1, nonsignificant test stimuli were introduced at the second, fourth, sixth, or eighth trial of the complex sequence of eight stimuli (i.e., a sequence comprised of varying standard stimuli). None of the test stimuli produced enhanced skin conductance responses under these conditions. Experiment 2 utilized the same design with only one difference: the test stimuli were presented following a simple stimulus sequence (i.e., repetition of a fixed standard stimulus). In this design enhanced skin conductance responses to the test stimuli were observed in almost all experimental conditions, with an advantage of a late over an early presentation of the test stimulus. Experiment 3 was designed to compare serial position effects of significant and neutral test stimuli. A serial position effect was obtained only for the neutral test stimuli, showing once again an advantage for late presentations. It was suggested that different mechanisms might underlie skin conductance responses to significant stimuli and to novel neutral stimuli.

Adult↗

PubMed1988

Selecting candidates for a medical school: an evaluation of a selection model based on cognitive and personality predictors.

Two studies were conducted to attempt to evaluate the selection procedures used in Hadassah Medical School. The predictors assessed were the Israeli high school matriculation examinations, a general aptitude test, an interview and a semi-projective test designed to assess personality pathology. In the first study 145 students of the 1975 and 1976 cohorts were assessed, the criteria being a combination of peer evaluations, evaluation of supervisors and academic record. Results showed the matriculation average score to be the only effective predictor for all criteria. In the second study 155 students of the 1979, 1980 and 1981 cohorts were assessed, the criteria being evaluation of supervising doctors, BSc grades and grades during the clinical period. Results again indicated that the matriculation test is the most effective predictor. In this study, however, the other variables added to the prediction of criteria based on clinical evaluations. The results were discussed, raising several possible explanations for the relatively high validity of the matriculation scores. It was suggested the matriculation scores capture personality dimensions, such as motivation and adjustment to the learning environment, which are important factors for success in medical training.

Aptitude Tests↗