Police officers' ability to detect deceit: The benefit of indirect deception detection measures

Purpose. The main aim of the experiment was to examine whether participants would be more accurate at detecting lies while using an indirect measure (i.e. ‘Does the person have to think hard?’) than while using a direct measure (‘Is the person lying?’). Method. A total of 39 police officers watched a videotape of a number of truth tellers and liars being interviewed. Participating police officers were randomly allocated to one of two experimental groups. In one condition, participants were asked whether each of the people they saw on the videotape was lying; in the other condition they had to indicate for each person whether that person ‘had to think hard’. Data were analysed in two ways: (1) the extent police officers could recognize lies and truths by using the two detection methods; and (2) behavioural and verbal cues the observers were actually looking for when answering the questions. Results. The results revealed that police officers could distinguish between truths and lies, but only by using the indirect method. Moreover, it was found that only by using the indirect method did they pay attention to the cues that were actual indicators of deceit. Conclusions. The findings suggest that the use of indirect methods might be useful for police officers when they attempt to detect deceit.