Deception Detection

Deception Detection


What is deception detection?


Deception detection refers to the investigative practices used to determine a person’s truthfulness and credibility. This is largely determined through the consideration of certain behavioral and physiological cues as well as larger contextual and situational information.


What methods are used to detect deception?


While historians are not entirely sure where or when deception detection practices originated, it is clear that humans have been trying to figure out how to tell if someone is lying for centuries. 

Fortunately, the methodologies have evolved drastically over time, shifting first from non-scientific testing (i.e., Salem Witch Trials) to more biologically-oriented ones (i.e., phrenology and graphology). Today’s deception detection generally combines behavioral psychology (i.e., human observation) and technology (i.e. polygraphs and artificial intelligence). 

Timeline Showing History of Deception Detection

Dr. Ekman’s work in the field of deception detection largely focuses on nonverbal communication of emotion observed in the face and body.

The challenges of deception detection

There is no single, definitive sign of deceit itself; no muscle twitch, facial expression, or gesture proves that a person is lying with absolute certainty. Therefore, most modern-day methods of deception detection heavily rely on a variety of methods to collect, analyze and interpret emotional and physiological data. 

However, any data collected merely expose emotional clues that may or may not be related to deception. For example, sweaty palms during a job interview could indicate an interviewee’s fear of being caught in a lie about their qualifications. Or, sweaty palms could be illustrating their fear that the interviewer won’t believe their qualifications despite being totally honest on their resume. Or, their palms could be sweaty because they’re worried about something else entirely, like a sick child at home.

There are still many more possible reasons why a person might experience sweating palms, especially during high stakes scenarios. To determine the actual cause, further investigation and analysis is needed. Jumping to conclusions, while easy to do, can be harmful to everyone involved and must be avoided.

Do lie detectors actually work?

The polygraph lie detector works on the same principles as detecting behavioral betrayals of deceit, and it is vulnerable to the same problems. The polygraph exam does not detect lies, just signs of emotion and requires further investigation.


What do lies look like?


Many observable signs have been linked to lying, but they are not always shown by everyone. The absence of these signals does not mean a person is truthful, but their presence, especially when there are multiple signs, is very suggestive of potential deceit.

An invaluable aspect in deception detection is first establishing a “baseline”, or behavior considered to be “normal” for the individual in question. The basic process of behavioral deception detection then involves looking for clues that signal some kind of change or deviation from this baseline. These can be noticed through “hot spots” across a number of different observable channels such as: facial expressions, body language, voice, verbal style and verbal content.

Chart Showing 5 Lying Signs to Observe

What is a "hot spot"?

Dr. Ekman coined the term “hot spot” to refer to signs that something is amiss; either that the full story is not being told or that details of the story are being falsified. Hot spots flag some kind of emotional or cognitive stressor though, importantly, do not reveal why. Further investigation and consideration of context is required to test your hypothesis. 

Typical hot spots are:

  • a deviation from baseline (e.g., a talkative child is uncharacteristically quiet when asked about a broken vase)
  • a momentary conflict between what is being communicated verbally and what is being presented nonverbally (e.g., assuring someone you don’t feel angry with them while clenching your jaw and raising your voice).

Facial clues to deceit


Micro Expressions

When lying, the face often contains two messages- what the liar wants to show and what the liar wants to conceal. Often, these hidden emotions leak in the form of a micro expression, a brief (half a second or less) involuntary facial expression revealing true emotion.


While Dr. Ekman cautions that a single micro expression or flash of leakage does not offer conclusive proof of lying, micro expressions are one of the most effective nonverbal behaviors to monitor to indicate a person is being dishonest.

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False Expressions

Any emotional expression can be falsified and/or used to conceal any other emotion. Across all emotions, studies have shown that often faked emotional facial expressions are asymmetrical. Some felt expressions are asymmetrical; it is just that most are not. 

In fear or sadness, a clue that an emotion is falsified is the absence of reliable forehead expression. 

A key clue that a happiness expression is false is when the eye muscles are not involved when smiling. The absence of movement in the outer part of the muscle that orbits the eye (orbicularis oculi pars lateralis, in Latin or AU 6 in FACS terms) distinguishes a fabricated smile from the genuine thing. This difference is sometimes difficult to recognize, and most of the time we are easily fooled by broad smiles that are fabrication, which might also explain why it is such a common emotional mask.


A lie catcher should never rely upon one clue to deceit; there must be many. The facial clues should be confirmed by clues from voice, words, or body. Even within the face, any one clue shouldn’t be interpreted unless it is repeated and, even better, confirmed by another type of facial clue.



Why is Dr. Ekman considered the world’s foremost human lie detector?


Dr. Ekman is irrefutably a leading expert in the field of human emotion and nonverbal expression. His work in these two areas tangentially led to a great deal of insight and expertise into the science of deception given the inherent links between the fields

However, Dr. Ekman does not consider himself to be a human lie detector and states that it is impossible for anyone to perfect the art of lie detection. Instead, he advocates that with more skills and data we can make determinations with greater certainty, though it’s important to remember that we can never know with 100% accuracy whether or not someone is lying. 

Lie Detection Expert - Dr. Paul Ekman

Even though Dr. Ekman rejects the title of “human lie detector”, it’s easy to see why others still call him that. Seeking his consultation, Dr. Ekman has worked closely with the world’s top security and anti-terrorism agencies including the FBI, CIA, and Scotland Yard. His prowess even attracted Hollywood executives, resulting in the hit tv show, Lie to Me

Wanting to prevent government or private entities from monopolizing this knowledge, Dr. Ekman translated his findings into online training tools for the public.


Additional Resources


Learn to recognize and respond to the emotional expressions of others with our online micro expressions training tools to increase your ability to detect deception and catch subtle emotional cues.


Expand your knowledge of emotional skills and competencies with in-person workshops offered through Paul Ekman International.


Delve into personal exploration and transformation with Cultivating Emotional Balance.


Build your emotional vocabulary with the Atlas of Emotions, a free, interactive learning tool created by Drs. Paul and Eve Ekman at the request of the Dalai Lama.


Read Dr. Ekman’s guide to emotions in his best-seller, Emotions Revealed


Additional Resources

Develop and hone deception detection techniques with Paul Ekman International’s three-day Evaluating Truthfulness and Credibility in-person workshop.
Discover how to heighten your communication skills, improve your emotional intelligence, and detect deception with micro expressions.
Inspired by Dr. Ekman’s expertise, learn about the science behind the television series and differentiate fact from fiction.