The Detection of Deception: The Effects of First and Second Language on Lie Detection Ability

An experiment was designed to test behavioural differences in the detection of deception arising from investigative interviews conducted in either a first or second language. A two (Cantonese or English) by two (deception or truthfulness) between-subjects factorial design was used. Twenty-six postgraduate criminology student observers provided judgments of lying in 20 video-taped interviews of undergraduate subjects randomly assigned to either telling the truth or lying about their opinions on capital punishment. Observers did less well in identifying liars in their first language but were more successful in identifying liars speaking in a second language. However, observers made more mistakes with those telling the truth in a second language. The degree that deceivers deployed countermeasures also varied with second language users reporting less ability to control verbal and non-verbal behavioural cues. Deceivers, irrespective of language, found lying required more cognitive resources than telling the truth and lying in a second language tends to alter one's facial expression or emotion. Behaviour associated with deception is discussed in the context of bilingual 'code switching' that appears to lessen cognitive load while lying and may be a potential marker of deception. Disbelieving-the-truth mistakes, or 'false positives' are as troublesome as false negatives and require attention in the context of cross-cultural interrogations.