Sophie Sowden, Gordon R.T. Wright, Michael J. Banissy, Caroline Catmur, Geoffrey Bird

The ability to detect deception is of vital importance in human society, playing a crucial role in communication, cooperation, and trade between societies, businesses, and individuals. However, numerous studies have shown, remarkably consistently, that we are only slightly above chance when it comes to detecting deception [1]. Here we investigate whether inconsistency between one's own opinion and the stated opinion of another impairs judgment of the veracity of that statement, in the same way that one's own mental, affective, and action states, when inconsistent, can interfere with representation of those states in another [2]. Within the context of lie detection, individuals may be less accurate when judging the veracity of another's opinion when it is inconsistent with their own opinion. Here we present a video-mediated lie-detection task to confirm this prediction: individuals correctly identified truths or lies less often when the other's expressed opinion was inconsistent with their own (experiment 1). Transcranial direct current stimulation (tDCS) of the temporoparietal junction (TPJ) has previously been shown to improve the ability to selectively represent the self or another [3-5]. We therefore predicted that TPJ stimulation would enable lie detectors to inhibit their own views, enhance those of the other, and improve their ability to determine whether another was presenting their true opinion. Experiment 2 confirmed this second prediction: anodal tDCS of the TPJ improved lie detection specifically when one's own and others' views were conflicting.