Expert Evidence

, Volume 7, Issue 1, pp 25-36

First online:

Accuracy and confidence in detecting truths andlies in elaborations and denials:Truth bias, lie bias and individual differences

  • Aldert VrijAffiliated withPsychology Department, University of Portsmouth
  • , Mark BaxterAffiliated withPsychology Department, University of Portsmouth

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Accuracy in the ability to detect truths and lies isimportant in a legal setting. It might be used as atool in police investigations to eliminate potentialsuspects, to check the truthfulness of informants orto examine contradictory statements of witnesses andsuspects in the same case. A consistent finding in thedetection of deception literature is the truthbias: People's accuracy at detecting truths isusually higher than their accuracy at detecting lies.The present article examines whether the existence ofa truth bias depends on the type of lie. It is arguedthat a truth bias may occur when people judgeextensive statements (e.g. elaborations), but that alie bias may occur when people judge statements whichdo not provide much verbal information (e.g. denials).Fifty participants (college students) were exposed to20 video fragments of 20 people telling elaborations(10) or denials (10). Half of the elaborations anddenials were truthful, the other half were deceptive.After each fragment, the participants were asked toindicate whether the person was lying or telling thetruth and how confident they were in their decisionmaking. As predicted, with regard to elaborations atruth bias was found and with regard to denials a liebias was found. In other words, people have difficultyin accurately judging deceptive elaborations andtruthful denials. The study further revealedindividual differences in participants' confidence atdetecting deceit. The more socially anxious/shy theparticipants reported themselves to be, the lessconfident they were in their ability to detect deceit.Also, the more extraverted they themselves reported tobe, the more confident they were in their ability todetect deceit. The importance of confidence onimproving people's ability to detect deceit will bediscussed.

detecting deception elaborations falsifications individual differences lie bias police truth bias