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The effects of diazepam and methylphenidate on the electrodermal detection of guilty knowledge Boisvenu, Guy Antonio


Sixty male undergraduate students participated in an experiment designed to investigate the effects of anti-anxiety and stimulant drugs on polygraphic interrogation. Subjects were randomly assigned to one of four groups. Three of the groups watched a 12 minute videotape depicting the burglary of an apartment through the eyes of the thief. Each subject was asked to imagine that it was he who was committing the crime and was given instructions to encourage his becoming absorbed in the videotape. Afterwards, they were accused of committing this crime. Each subject received one of three look-alike capsules containing a drug which, they were told, would help them to escape detection. Capsules for the first group contained 10 mg of diazepam; those for the second group, 20 mg of methylphenidate; a placebo was given to the third group. Subjects in the fourth group, the innocent control condition, viewed a 10 minute videotape sequence showing the interior of another apartment, this time with no crime committed. They did not receive any medication or placebo after they were accused of committing the crime. After a one hour wait, all subjects were interrogated by the experimenter, who was blind to both their guilt or innocence and drug status. Skin conductance, heart rate and respiration were monitored; all charts were scored blindly. No drug effects were found in the guilt/innocence classification or in any of the physiological channels being monitored. The overall hit rate, including inconclusives, was 81.7%. A significant relationship between recall of guilty information and detectability was also found.

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