(In)Consistencies as Cues to Deception

Abstract: The aim of this thesis was to examine statement consistency types (between-statement consistency, within-statement consistency, within-group consistency, and statement-evidence consistency) within various contexts of deception. In Study I (N = 150), between-statement consistency was examined when question format was changed across two interviews. Participants provided free recall accounts of two events in the first interview. In the second, they either freely recalled the events again or responded to specific questions sequentially (one event at a time) or non-sequentially (both events together). Liars uttered fewer repetitions across interviews (less between-statement consistency) than truth tellers, particularly when questions were non-sequential, but they unexpectedly showed more within-statement consistency than truth tellers. In Study II (N = 98), the Devil’s Advocate approach was used to investigate within-group consistency for opinions. Pairs of participants who shared strong opinions about a controversial topic were matched and permitted to prepare for individual interviews about their true/false opinions. They were asked an ‘opinion-eliciting question’ for arguments supporting those opinions followed by a ‘devil’s advocate question’ for opposing arguments. Prepared truth telling pairs were more consistent with each other on the opinion-eliciting question than on the devil’s advocate question. As predicted, deceptive pairs were equally consistent in response to both questions. In Study III (N =144), the effects of counter-interrogation strategies and familiarity with the alibi on statement-evidence consistency and between-statement consistency were examined. All participants visited a restaurant for 10 minutes (high familiarity) or 30 seconds (low familiarity) to use it as an alibi in two interviews involving visuospatial tasks. Liars who knew about the interview technique prior to committing a mock crime provided significantly more non-salient (particularly if they were highly familiar with the alibi) and salient details than truth tellers and liars who did not possess this knowledge, but they did not differ on statement consistency types. In Study IV (N = 71), police officers were surveyed about their perceptions of suspects’ statement (in)consistency types. Officers were most likely to look for statement-evidence inconsistency and least likely to look for within-statement inconsistency. This finding was explained by their belief that liars attempt to eliminate within-statement inconsistency more than other types of inconsistency unless incriminating evidence is strategically disclosed during the interview. The results of this thesis extend previous findings demonstrating that liars attempt to maintain statement consistency types unless specific interview techniques are used to increase differences between liars and truth tellers. Critically, familiarity with the reported event seems to help both liars and truth tellers to provide consistent statements, whereas counter-interrogation strategies may fail or may succeed at the expense of one or more consistency type(s). Practitioners need to be aware of these effects and to consider all consistency types simultaneously rather than separately to detect deception.