Drawing out the truth

Forget expensive fMRI-based lie detection or iffy polygraph tests, give your suspect a pencil and paper and get them to draw what happened - a new study suggests their artistic efforts will betray whether they are telling the truth or not.

Aldert Vrij's new study involved 31 police and military participants going on a mock mission to pick up a package from another agent before delivering it somewhere else. Afterwards the participants answered questions about the mission. Crucially, they were also asked to draw the scene of the package pick-up. Half the participants acted as truth-tellers, the others played the part of liars.

Vrij's team reasoned that clever liars would visualise a location they'd been to, other than where the exchange took place, and draw that. They further reasoned that this would mean they'd forget to include the agent who participated in the exchange. This thinking proved shrewd: liars indeed tended not to draw the agent, whereas truth-tellers did. In fact, 80 per cent of truth tellers and 87 per cent of liars could be correctly classified on the basis of this factor alone.

'These are high accuracy rates and will be difficult to exceed by any traditional verbal, nonverbal or physiological lie detection tool,' Vrij's team said. 'In fact, we would certainly expect such tools to fare worse.'

Another distinguishing factor was the perspective of the drawing. Fifty-three per cent of truth-tellers penned a drawing from their own first-person perspective at the scene; 47 per cent opted for a birds-eye view. By contrast, 81 per cent of liars went for the birds-eye view and just 19 per cent for the first-person perspective.

The researchers said theirs was the first study of its kind and they acknowledged many questions were left unanswered. 'We believe that our findings justify taking drawing seriously as a lie detection tool, and that it will encourage researchers to carry out drawing research.'
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Vrij, A., Leal, S., Mann, S., Warmelink, L., Granhag, P., & Fisher, R. (2010). Drawings as an innovative and successful lie detection tool. Applied Cognitive Psychology DOI: 10.1002/acp.1627