This study is based on a Ph.D. thesis conducted by the first author under the supervision of the second author. The authors would like to thank Dr. Joseph Almog, head of the Division of Criminal Identification. Israel National Police, and Dr, Avital Ginton, head of the Behavioral Section, for permission to use the Scientific Interrogation Unit's equipment in this research. The authors also wish to express their appreciation to Mr. Murray Kleiner, for his help in testing subjects and in evaluating the polygraph charts, and to Talta Robobitz, for her assistance in conducting the laboratory experiment.
Effects of Motivation and Verbal Response Type on Psychophysiological Detection of Information
Version of Record online: 30 JAN 2007
Volume 26, Issue 4, pages 442–451, July 1989
How to Cite
Elaad, E. and Ben-Shakhar, G. (1989), Effects of Motivation and Verbal Response Type on Psychophysiological Detection of Information. Psychophysiology, 26: 442–451. doi: 10.1111/j.1469-8986.1989.tb01950.x
In a reanalysis of Bradley and Warfield's (1984) data we tested whether the mean detection score of informed innocent subjects was greater than a chance expectation score. Using a normal approximation to the detection in dex distribution, it was demonstrated that the mean detection score based on the pooled data of all three informed innocent groups was significantly greater than chance (Z = 2.30, p < .05).
- Issue online: 30 JAN 2007
- Version of Record online: 30 JAN 2007
- (Manuscript received June 8, 1988; accepted for publication September 21, 1988)
- Guilty Knowledge Technique;
- Detection of deception
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 × 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.