An Investigation of the Guilty Knowledge Test Polygraph Examination

The Guilty Knowledge Test (GKT) is a psychophysiological questioning technique that can be used as part of a polygraph examination which purports to assess whether suspects conceal “guilty knowledge” by measuring their physiological responses while responding to a series of multiple choice questions. The present study sets out to consider a number of key issues in relation to the GKT paradigm. Specifically, the following questions were considered: Does response mode matter? Does motivation influence outcome? Are combined physiological measures better than single ones? Does gender have an effect on physiological responsivity during a polygraph examination? Results demonstrated real variations between the physiological measures used. Gender differences were also observed in polygraph response patterns. These findings are discussed in relation to the validity of the Guilty Knowledge Test.