Discrepancy between our own values and another's can impair lie detection

One of the key barriers to successfully tell if someone is lying is inconsistency in the opinions between the person trying to detect a lie and the individual they are judging, according to a new study led by the Institute of Psychiatry, Psychology & Neuroscience (IoPPN).

The findings, published in Current Biology, suggest that we are consistently poor at detecting deception and only slightly better than chance at detecting lies; 54 per cent compared to 50 per cent.

However, we may be able to improve our own lie detecting capabilities by actively taking into account that our opinions may differ from those of someone else, and by selectively paying attention to their opinion, whilst inhibiting our own.

In the first experiment in this study, researchers at the Medical Research Council (MRC) Social, Genetic and Developmental Psychiatry Centre, IoPPN at King’s College London, tested how well people were able to detect lies if another’s views differed from their own. When the opinion of the person detecting the lie and the person being judged were the same, truths and lies were successfully identified 55 per cent of the time. But this fell to 51 per cent if their views on the topic were different.

To demonstrate which area of the brain might help us to prevent our own views clouding our judgement when detecting lies, the researchers delivered transcranial direct current stimulation to a part of the brain that influences our representations of ourselves and others. This improved lie detection when views were inconsistent to 60 per cent.

Sophie Sowden, lead researcher based at the MRC Social, Genetic and Developmental Psychiatry Centre at King’s College London, said: 'While there are many other factors at play when we try and detect if someone is lying, by understanding that our own views can cloud our judgement we can find one small way to improve our lie detection abilities. If an individual is confronted with an opinion that differs from their own, their lack of experience in justifying that stance means they are less able to judge the veracity of the statement.'

While the technique used in this study is useful to understand more about the processes underlying lie detection, it can’t be used to improve our abilities to spot liars in our everyday lives.

There is little evidence that the impact of brain stimulation can be sustained over long periods of time and the improvements, whilst noticeable, were still minimal. The improvement in lie detection success to 60 per cent still falls some way short of the 87 per cent accuracy achieved by polygraph tests. Despite this, the research provides clues as to how our opinions can affect our ability to judge whether someone is lying.

This study was funded by the MRC and the Economic and Social Research Council.

Notes to editors

Paper reference: Sowden, S et al (2015) ‘Transcranial Current Stimulation of the Temporoparietal Junction Improves Lie Detection’ Current Biology

For further media information please contact Jack Stonebridge, Press Officer, Institute of Psychiatry, Psychology & Neuroscience, King’s College London on +44 (0) 20 7848 5377 or jack.stonebridge@kcl.ac.uk.

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