Detecting self-deception in a leader, in a colleague, or in oneself is an essential step in preventing behavior that is self-destructive and damaging to others. There are definite signs of self-deception. Some cues are overtly verbal, some are exposed through someone’s writing, and some are more hidden in nonverbal communications. These signs can leak out from an individual who tries to hide them as they exact their taxing mental strains. The antidote to a leader barreling down the path of self-destructive behavior caused by self-deception and taking the organization with them is self-awareness.
Why Detecting Self-Deception is Important
Individuals should first recognize the characteristics of self-deception so they can better identify when they, or others, are being self-deceptive. Understanding how, when, and in what form self-deceivers display the tell-tale signs of self-deception will increase one’s ability to spot these behaviors and will decrease their likelihood of being vulnerable to the phenomenon of deceiving oneself.
Detecting such behavior is evolutionarily advantageous. Self-deceptive behavior can be costly in interactions with members inside one’s in-group. From an evolutionary perspective, the in-group may be a tribe. From a contemporary perspective, an in-group may be a work or social group. When interacting within the social commune one belongs to, the overlap of self-interest and group interest plus the feedback provided by in-group members can serve to discourage self-deceptive behavior in a group member, thus, giving some partial correction to the behavior. 
Such in-group members may not see the dangers to the group until it’s too late. Cooperation and reciprocity within a group are fundamental in cognitive adaptation to in-group hierarchies. Detecting those in-group members who are attempting to cheat the in-group, either through outward deception or by deceiving themselves to deceive other members, has always been crucial to the survival of the in-group.
Delroy Paulhaus and Kevin Williams studied the differences in individual personalities of what they called the Dark Triad: Machiavellianism, narcissism, and psychopathy. Narcissists, those who are more self-centered, egocentric, and fascinated with themselves, exhibited the most significant self-enhancement. That is, they over-claim their knowledge on any subject, which triggers a response bias that favors one’s overinflated view of their attributes. On the other hand, Machiavellians (those characterized by a manipulative personality) showed almost no signs of self-enhancement. Narcissists and Machiavellians exhibit more malevolent personalities. These people show different levels of self-deception that Paulhaus and Williams attributed partially to their frustration from their inability to communicate their ideas effectively. 
Giving Themselves Away
Self-deception may be difficult to detect. In my interview with Anthony Pratkanis, he acknowledged that it’s difficult to detect self-deception because self-deception is internal to that person. However, there are sometimes signs that someone is feeling the stress of lying. Behavior that one intends to keep hidden may leak out.
If one knows what the signs of deception look like as they emanate from a deceiver, then one can uncover an intent to deceive. A person who intends to deceive others must keep the lies straight in their heads while at the same time guarding against letting indicators slip that they are engaged in a juggling act with truths and fabrications. This is no easy task, and signs of this struggle are bound to slip out for their targets to see. Deceiving oneself or others creates stress, guilt, and fear in the deceiver. The added cognitive burden of hiding the truth and dealing with the consequences on the mind may make such activity detectable.
Verbal Communication and the Written Word
Leaking indicators of something afoot can take many forms. Researchers have identified verbal, nonverbal, and written indicators that something wicked may be in the works. Language euphemisms, vague expressions, and more disarming word substitutions in written and spoken language for something negative are ways deceivers downplay their true intent. Deceivers may replace morally repugnant language, which is sure to raise suspicion, with more abstract, vague, and neutral verbiage and descriptors. They may do this in the hopes of concealing the immoral or unethical implications of their intentions and actions. 
Russell Craig, Tony Mortensen, and Shefali Iyer used a case study of Ramalinga Raju, Chair of Satyam, a multinational Indian company, to illustrate this point. Raju confessed to deceptive conduct as Chair of Satyam in 2009. These researchers examined his annual report letters prior to his admission of guilt to discover his overt signs of deception. They observed over the course of the years preceding his confession that Raju’s language in his written communication changed. His letters began to give away his deceptive behavior. They analyzed his letters for changes in the use of personal pronouns, positive and negative words, the intensity of the words, tone of speech, and the diversity of his language. Raju’s changing word choice was exposing his secrets even before he confessed to his dishonesty.
On top of controlling what one says and writes, someone practicing deception must also manage their physical actions. They must control their body language and facial expressions to maintain credibility and the consistency of their story and the congruence between what they say, write, and exhibit through actions. This is an even higher cognitive task that creates more stressful side effects. Under scrutiny from colleagues or superiors, the added mental burden may be too much to bear, leading to a slippage of the truth.
Theories about deception detection have stated that deceivers leak tells indicating that they are lying. They leak emotional states through facial expressions and other nonverbal communications. However, Truth-Default Theory (TDT), by Timothy Levine, holds that reliance on detecting these tells proves to be an inaccurate detection aid. Lies are better detected by comparing what is said by an individual to what is known and less detected by verbal, nonverbal, and written signs. Deception is not usually detected in real time through passive observation, and is usually discovered after the fact based on confessions or the discovery of evidence.
Although self-deception is an internal phenomenon, there are external signs that give this dishonesty away. Self-deceivers may display verbal, nonverbal, and written indicators that the stress of lying is taking a mental toll. Detecting that someone is self-deceiving is the first step in rooting out and correcting this destructive behavior.
self-deceptive and others-deceptive behavior can be costly in interactions within a group
signs of deceptive behavior can leak out in the form of verbal, nonverbal, and written communication
 Pienaar & Nel (2017)  Caldwell (2009)  Trivers (2006)  Cummins (1999)  Paulhaus & Williams (2002)  Pratkanis, A., in discussion with the author (February 2021)  Nicolaides et al. (2018)  Vrij et al. (2000)  Tenbrunsel & Messick (2004)  Craig et al. (2013)  Porter & Brinke (2010)  Von Hippel & Trivers (2011)  Levine (2014)