If you were a police officer, what sort of interview style would offer you the best chance of detecting whether or not your interviewee was telling lies? Aldert Vrij and his colleagues ran a study to find out:
In Experiment 1, we examined whether three interview styles used by the police, accusatory, information-gathering and behaviour analysis, reveal verbal cues to deceit, measured with the Criteria-Based Content Analysis (CBCA) and Reality Monitoring (RM) methods. A total of 120 mock suspects told the truth or lied about a staged event and were interviewed by a police officer employing one of these three interview styles. The results showed that accusatory interviews, which typically result in suspects making short denials, contained the fewest verbal cues to deceit. Moreover, RM distinguished between truth tellers and liars better than CBCA. Finally, manual RM coding resulted in more verbal cues to deception than automatic coding of the RM criteria utilising the Linguistic Inquiry and Word Count (LIWC) software programme.
In Experiment 2, we examined the effects of the three police interview styles on the ability to detect deception. Sixty-eight police officers watched some of the videotaped interviews of Experiment 1 and made veracity and confidence judgements. Accuracy scores did not differ between the three interview styles; however, watching accusatory interviews resulted in more false accusations (accusing truth tellers of lying) than watching information-gathering interviews. Furthermore, only in accusatory interviews, judgements of mendacity were associated with higher confidence. We discuss the possible danger of conducting accusatory interviews.
In the discussion, Vrij and colleagues summarise:
The present experiment revealed that style of interviewing did not affect on overall accuracy (ability to distinguish between truths or lies) or on lie detection accuracy (ability to correctly identify liars). In fact, the overall accuracy rates were low and did not differ from the level of chance. This study, like so many previous studies (Vrij, 2000), thus shows the difficulty police officers face when discerning truths from lies by observing the suspect’s verbal and nonverbal behaviours.
In other words, if law enforcement officers want to increase their chances of detecting deception, they need to make sure interviewers use an information gathering approach. But simply watching that interview (live or on tape) might not help them decide whether or not the suspect is telling the truth – they may need to subject a transcript to linguistic analysis to give themselves the best chance.
Even if it doesn’t result in better ‘live’ judgements of veracity, an information gathering approach has another advantage for the law enforcement officer: it maximises the number of checkable facts elicited from the suspect, and being able to check a fact against the truth is pretty much the most effective means of uncovering false information. Of course, someone can provide false information without deliberately lying: if they have misremembered something, for instance, or are passing on something that someone else lied to them about. But then the point of any law enforcement interview is to get to the truth, which is a higher goal than simply uncovering a liar, in my opinion.
As always with lab-based studies, there are some limitations. Vrij et al., for instance, acknowledge that “in practice elements of all three styles may well be incorporated in one interview” but explain that “we distinguished between the three styles in our experiments because we can only draw conclusions about the effects of such styles only by examining them in their purest form”.
Further problems, which are difficult to overcome in structured lab settings, are caused because participants were assigned randomly to ‘guilty’ (liars) or ‘innocent’ (truth tellers) conditions. In the real world, individuals who are prepared put themselves in a situation in which they might later have to lie may differ in their ability to lie effectively than those who try to stay out of such situations. And real guilty suspects make a decision about whether they are going to lie (a few confess from the start, others will offer partial or whole untruths). It’s an issue that is open to empirical test: let participants choose whether they want to be in the ‘guilty’ or ‘innocent’ conditions (or have four conditions: guilty choice/guilty no choice/innocent choice/innocent no choice).
Also, in this study the liars were told what lie to tell (as opposed to being able to make one up). Real guilty suspects who decide to lie will presumably choose a lie that they they think they stand a good chance of being able to get away with. In real world conditions, the perception by the guilty individual of what sort of situation they’re in, the evidence against them, the plausible story they can tell to explain away the evidence, and their ability to lie effectively are probably all important.
Photo credit: scottog, Creative Commons License