The role of comparison questions in physiological detection of deception

Comparison questions in physiological detection of deception were studied with 60 "guilty" and 60 "innocent" participants in a mock crime experiment. Different types of comparison questions were used in four conditions: relevant-irrelevant (R-I) participants answered only relevant and neutral questions; trivial directed lie participants were instructed to lie to three of the six neutral questions; personal directed lie participants were instructed to lie to personally relevant questions; and probable lie participants received traditional probable lie comparison questions. Respiration, cardiovascular, vasomotor, and electrodermal activity were recorded. Manipulation of the comparison questions produced different patterns of physiological responses for innocent but not for guilty participants. The R-I test produced an unacceptable rate of false positive decisions.