"I Know You're Lying," the keys to becoming a better lie detector, by Paul Ekman
This topic may seem far removed from marketing and neuroscience. However, Paul Ekman, a renowned American psychologist known for his work in the field of emotion recognition and deception, has contributed to the vast field of neuromarketing. His work on the identification of six universal emotions, his work on recognizing microexpressions and their potential meanings, and his study of behaviors that can betray a liar have contributed to our understanding of consumer behavior.
In his book “I Know You’re Lying,” Ekman explores the complex world of lying, drawing on decades of research in psychology, facial expression, and behavioral analysis. We will review the main points and key concepts to take away from his book.
1. Not all lies are equal
Lying isn’t just about making up a story. There are several forms of lying: omission (not telling the whole truth), concealment (hiding a key element), and falsification (pure fabrication). These distinctions are important because they imply very different levels of complexity and detection.
🔍 Example: A freelance consultant claims to have “worked with CAC 40 companies.” In reality, he was simply a subcontractor. He didn’t lie in the strict sense, but he intentionally gave a distorted image of reality.
🎯 In marketing: This type of vague communication may be attractive in the short term, but it undermines trust. And in a world saturated with information, trust is the most valuable currency.
2. Lying involves a deliberate intention to deceive
An essential point: a lie is not simply a mistake or an inaccuracy. What characterizes it is the intention to deceive. It is this ethical and conscious dimension that distinguishes a lie from simple clumsiness.
🔍 Example: A web professional republishes an old customer testimonial, presenting it as “very recent” to attract new prospects. This is not a careless error: it is a deliberately misleading strategy.
🎯 Food for thought: Any communication that aims to manipulate perception without any real basis is a form of lying. Transparency then becomes a powerful marketing strategy.
3. Emotions are not easily hidden.
Even when we try to hide an emotion, it can leak through our gestures, our tone of voice, or especially our face. What we feel deeply ends up showing through, sometimes without our knowledge. This is when the body “speaks in spite of ourselves.”
🔍 Example: During a Zoom call, an employee assures us that everything is going well on the project, but their brow furrows slightly when it comes to discussing deadlines. This micro-change, imperceptible to many, may be an indication of anxiety they are trying to hide.
🎯 In communication: By picking up on these weak signals, we become better able to detect misalignments between what we say and reality. This allows us to adapt our communication in real time
4. Microexpressions are the fingerprints of emotions
A microexpression is a facial expression that lasts less than half a second. It appears before the brain regains control. These emotional micro-cues are universal (present in all cultures) and almost impossible to inhibit.
🔍 Example: A customer examines your quote. They smile politely, but a micro-expression of rejection (puckered upper lip, slight sneer) appears for a moment. They don’t say anything, but this nonverbal signal suggests that they find the price excessive.
🎯 In communication: By refining our ability to spot these micro-expressions, we can better decode the other person’s real reactions—beyond their words.
5. Lying uses more mental energy
Lying is cognitively costly: you have to invent a credible version, remember what you said, manage your body language, and control your emotions. This extra mental activity can lead to inconsistencies, hesitations, or unusual behavior.
🔍 Example: During an interview, a candidate claims to have run a viral campaign. He searches for words, avoids concrete details, and gives a vague account. The lack of spontaneity and precision is revealing.
🎯 In business: Authentic communication is fluid and natural. A story that’s too well-crafted, without any rough edges, can sometimes be a red flag.
6. Stress ≠ lies
This is a fundamental point: a stressed person isn’t necessarily lying. Stress can come from anxiety, social judgment, or introversion. It’s therefore important to avoid jumping to conclusions based solely on nervous behavior.
🔍 Example: A startup founder sweats profusely during a pitch. He stammers, looks at his cards. He’s not a liar: he’s just unaccustomed to public speaking.
🎯 The trap: Mistaking stress for a sign of lying is a classic mistake. Ekman emphasizes the importance of combining several clues before making a judgment.
7. Some emotions are easier to play than others
A social smile is easy to imitate. However, emotions like fear, anger, or disgust involve involuntary muscle groups and are therefore much more difficult to simulate.
🔍 Example: A salesperson says he’s excited to sign a contract, but his smile doesn’t touch his eyes: no crow’s feet, no genuine crinkle. It’s a fake smile, with no real emotion behind it.
🎯 In marketing: A video with an inauthentic smile can cause discomfort in the audience, even without them knowing why. The human brain is wired to detect authenticity.
8. The higher the emotional stakes, the more likely leaks are.
When the pressure increases (personal stakes, stress, fear of being exposed), the liar is more likely to let slip signs. Emotion takes over rational control.
🔍 Example: A freelance subcontractor discovers a major technical problem before delivery. In a meeting, he assures everyone that everything is “managed,” but his breathing accelerates and he blinks more frequently—physiological warning signs.
🎯 Key takeaway: It’s in situations of high emotional intensity that leaks are most visible—if you know how to spot them.
9. Les indices ne sont pas uniquement visuels
Le mensonge s’entend aussi dans la voix (intonation, débit, silences), dans les mots employés (langage flou, contradiction), ou dans les gestes (auto-contacts, agitation des mains). L’analyse du mensonge est multidimensionnelle.
🔍 Exemple : Un client dit “je suis sûr que ça ira”, mais son ton monte à la fin de la phrase, comme s’il posait une question. Son débit ralentit. Cela peut trahir un doute non exprimé.
🎯 En entretien ou prospection : Prêter attention au rythme de parole, aux silences ou aux formulations (“je pense que…”, “peut-être que…”) peut fournir des informations précieuses.
10. Plus on connaît quelqu’un, plus il est difficile de croire qu’il ment
Les relations de confiance peuvent aveugler. On accorde plus de crédibilité à ceux que l’on apprécie ou côtoie régulièrement. Pourtant, les personnes les plus proches peuvent elles aussi mentir – parfois même plus habilement.
🔍 Exemple : Un associé de longue date affirme avoir rempli sa part du travail. Vous le croyez sur parole… mais découvrez qu’il a pris du retard sans rien dire. Votre biais de confiance a brouillé votre vigilance.
🎯 Le piège : Croire que seuls les inconnus mentent est une erreur fréquente. Ekman démontre que l’intimité n’est pas un filtre fiable pour détecter le mensonge.
En conclusion : Pourquoi est-ce si précieux dans notre métier ?
Comprendre les mécanismes du mensonge, c’est développer une écoute plus fine, une lecture plus précise des signaux faibles, et une capacité à ajuster son discours pour créer des relations plus sincères. C’est aussi un levier de différenciation pour toute personne travaillant dans la communication, la vente ou le marketing.
Dans un monde saturé de discours trop bien calibrés, l’authenticité est la clé.