Instead of showing a true self, one would prefer to censor own self so as to be perceived in a positive light. According to Hart, Fillmore, and Griffith (2009), psychological lies would be used for self-protection, avoiding conflict and tension and minimization of ill will and hurt feelings. The history of psychological measures of deception such as the use of polygraphs has long been in existence. Recently, researchers have sought to identify liars by measuring their brain activity (Kranacher, Riley & Wells 2011). However, Hart, Fillmore, and Griffith (2009) indicate that such psychological measures indirectly measure lying and hence the concern for validity. Speech content could reveal deception especially if the observer knows that what is being said is untrue. Comparing statements from the liar to facts could reveal deceit (Vrij 2008). Hence, it would be critical for the listener to identify any verbal cues that could lead to the identification of deceit. As argued by Gamson et al. (2012) and Kapardis (2003), verbal cues have generally been accepted as being more reliable than non-verbal cues in detecting lies. An attentive listener would, therefore, be able to identify such cues.
Liars at times face guilt and could be afraid of getting caught. This fear would cause such persons to become more nervous and concerned than those telling the truth. This is the guiding principle used to detect lies as given in police manuals (Hartwig, Granhag & Strömwall 2002; Matsumoto, Hwang, Skinner & Frank 2011; Vrij, Granhag & Porter 2010; Whelan, Wagstaff & Wheatcroft 2013). Detecting such emotions in a liar’s speech would involve being sensitive to their guilt and fear which according to Vrij (2008) could be expressed verbally when liars make negative comments. Negative comments like hate, dislike, useless, uncomfortable and the likes reflect negative affect which could reveal deceit.