Deception is much harder to spot than most people think.
We all have ideas about what it looks like: shifty eyes, fidgeting, bouts of bull and bluster. But even honest people, under pressure, will exhibit most of those symptoms.
I'd like to share with you some of the techniques that are fast becoming best-practice amongst the leading researchers and practitioners of investigative interviewing.
Spotting the liar
Concocting a lie is difficult. It's harder to tell a lie than the truth. The process sucks up our brain's effort and energy as it marshals its resources to create an alternative version of events.
When so much of our energy is being expended on creating the lie, other activities such as body language, verbal interaction and eye contact start to show the strain. If we can increase that ‘cognitive load' on someone we suspect is lying to us, we may spot the tell-tale signs of their deceit more easily because they will occur more often.
Research suggests that the tell-tale signs of deceit when we add cognitive load include...
- more or less blinking than in the baseline behaviour
- more pauses than in normal baseline communication
- fewer and/or smaller hand/finger movements than in normal baseline communication
- less direct language, for example ‘the table was knocked over' as opposed to ‘Jim knocked over the table'
- fewer ‘I' references than are used in normal baseline communication.
So how do we get cognitive load working in our favour? Here are some ethical and effective tactics to help you increase the cognitive load on your interviewee and raise your chance of spotting the liar...
- Impair their storytelling ability. Ask them to recall events in reverse order. A lie is made up from beginning to end and recalling it backwards is very difficult, maybe impossible. At the very least, it will add some serious cognitive load to the poor brain as it attempts this process.
- Insist on direct eye contact. Asking interviewees to maintain eye contact with you also adds load by forcing them to concentrate on several things at once. Since the brain only has a limited amount of energy to use for these tasks, it becomes harder to complete them simultaneously.
- Ask odd questions, after the free recall stage is complete. Ask spatial or temporal questions that go beyond coaching or preparation. Here are some examples...
- Spatial questions: ' Where did the owner sit? What could you see from where you were?' In a research test, interviewers spotted the liars 80% of the time when they used spatial questions.
- Temporal questions: ‘What time were you there? How many others were there? How long did it take? When did you notice...? How long before...?' Time is most often what interviewees lie about when they have scripted their version of events. In the test, liars were caught 55% of the time when interviewers used temporal questions.
A lie is not stable like the truth. So keeping all the pieces straight in our head becomes more difficult as the lie grows in complexity. Telling the story under increased cognitive load may reveal new information and reveal any discrepancies.
Art as interview
Imagine you have interviewed your subject, and you believe there are some inconsistencies with his story. You have tried changing the order of the recount and added in spatial and temporal questions. You have a lot of information now, but you may still be confused about what really happened.
Try this: Ask your interviewee to draw the event as he experienced it.
Drawing is effective as an addition to the cognitive interview, where the interview is about an event, because...
- it transcends speech so it's effective with foreigners, disabled people or children
- it provides an immediate assessment tool for information already collected
- it's easy to apply as a technique and materials are readily available
- it's easy to check for accuracy against statements
- different people can be ‘interviewed' at the same time.
Drawing is a wonderful tool because it's unpractised, it's unanticipated and it forces the interviewee to take a position.
Incidentally, liars were also more likely to use an aerial shot for their diagram, whereas truth-tellers were more likely to draw the event as if they had filmed it with a camera on their shoulder. If you need any more persuasion, interviewers caught liars 75% of the time when they used drawing as an addition to the cognitive interview.
Points to ponder
If we want to catch liars in the act we need to rethink our beliefs about what liars do so that we can look for the real indicators of deception.
We need to become fluent at using cognitive interview methods such as PEACE so that we get good quality information to assess. And we need to use techniques that add cognitive loading so we can spot the spontaneous and the rehearsed liar more often and with greater accuracy.
For more information on this topic see research articles by Vrij, Leal, Mann, Warmelink, Granhag and Fisher; 2009, Sperry and Hillman; 2008, De Paulo et al; 2003, Buller and Burgoon; 1996.
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