Detecting Lies through Behavioral Changes

Detecting lies can be difficult. It's helpful to look for red-flag behavioral changes.

loss prevention investigator, detcting lies

Many people believe when an individual refuses to make eye contact there is a strong indication the person is being deceptive. People also believe the gestures of the hands and arms while telling a story is an indication of a lie being told.

Academic researchers have spent a considerable amount of time learning what behaviors investigators rely on to determine if an individual is being deceptive. Researchers have also decided our ability at detecting lies is at a chance level: 50-50, a flip of a coin. In a classroom setting with low levels of stress on the study participants and using an artificial experience, it is extremely difficult to detect a deception. However, this is nothing like the real-world situations we work in where a person’s liberty, reputation, and livelihood might be at risk. Our experience indicates that investigators are much better at detecting lies than chance levels.

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Spotting Concern

Academics have studied individual behaviors looking for that single, nonverbal cue that strongly indicates a person is lying. Not surprisingly, they have not identified a single behavior that always strongly indicates an individual is being deceptive. In fact, most behaviors, when viewed individually, are not strongly associated with deception. This shouldn’t be surprising since people will often lie differently within several sentences. For example, in one instance a person might cross their arms, while in another they may avert their eyes, and then in another situation they may lock themselves in place.

The best lie detectors are not looking for individual behaviors, but rather one-time changes in behavior that indicate a potential concern. We could call these spots of behavioral change red flags, hot spots, concerns, trigger points, or any other name, but they indicate a moment of stress in the dishonest employee or other subject with whom we are speaking. These behaviors may be triggered by a change of topic, presentation of information, use of a particular word, or a question posed by the interviewer and can occur in a variety of conversations.

Establishing a behavioral norm for an individual before beginning the interview is an important component in establishing a baseline of behavior for comparison. When a change of behavior is noted, it may be due to a number of reasons:

  • The individual was deceptive
  • The individual was surprised by the inquiry or topic
  • The individual was fearful of a secondary issue
  • The individual was concerned about their previous statements in light of new information
  • The individual was embarrassed

A person who is embarrassed or concerned about a secondary issue may, in fact, offer behavioral clues or concerns that would be similar to the deceiver.

In the context of this post, we will use Dr. Paul Ekman’s definition of lying: “Lying is an act whereby someone deliberately misleads another and does so without notifying that person that he or she will be misleading them. The key here is that the individual is deliberately and knowingly presenting inaccurate information to another to conceal the real situation.”

Unfortunately, when we observe a behavior occurring at a particular point in the conversation, we may not be able to discern whether the individual is lying to us, is concerned about some other issue, or whether the behavior was an anomaly. What we can do is further explore that particular area of the conversation to determine the true reason for the behavioral change and its consistency.

Cognitive Load

The interviewer has several advantages, both physiologically and psychologically, to assist them in determining whether the subject is attempting a deception. The autonomic nervous system causes physiological changes in the body in response to emotions, such as fear, in order to protect the individual by preparing them to fight or flee. These emotional triggers cause changes such as an alteration of the breathing pattern, dilation of the pupils, blanching or flushing of the skin, perspiration, or any of a multitude of other notable observations.

Besides having to deal with the physiological changes of the body, the liar must also cope with psychological changes and related pressures that manifest on the individual’s thought process. Researchers call this “cognitive load.” Essentially, cognitive load is the pressure an individual is under when they are thinking on their feet as they attempt to lie, continue to lie, or decide what to do next.

There are several behaviors an interviewer can observe that indicate a person is thinking about their answer. By the way, just because a person is thinking about their answer does not mean they are attempting to deceive. They may merely be gathering their thoughts to provide a thorough answer. The context of the person’s pause should provide the interviewer with some sense of whether there is an attempt to deceive in play or an effort to make sure the answer is correct.

When an individual attempts to deceive, they must balance the lie against what they believe might be known or potential evidence that could contradict their statements. Clearly, this will require time to evaluate their situation before they present their next statement. This pause will often cause the deceiver to appear tense, stiff, and less cooperative in giving a complete rendition of events. The more general a lie, the easier it will be to avoid contradictions with other witnesses or evidence. Simply stated, the less detailed the lie, the safer it is to tell.

The easiest type of lie for a person to tell is one that reduces the cognitive load and the concern about contradictory witnesses or evidence. That type of lie is a lie of omission. A lie of omission uses the truthful events while omitting those details that would be incriminating. “I went to the mall this afternoon and then came back to the house.” Here, the deceiver left out the fact that between leaving the mall and arriving home, they had robbed a convenience store. Otherwise, their story is the truth. Because of the general nature of the story, the liar can alter or fabricate information or other details if it proves necessary later.

Cognitive load, or thinking, requires time to decide what to say next. To cover their delay, the deceiver may use a variety of tactics, such as repeating the question, offering non-responsive statements before answering the question, body shifts, hand and arm movements, created jobs, and language artifacts, such as “ah,” “um,” or clearing the throat. Another common response is for the subject to sit stiffly with little or no movement of the arms and body while the individual focuses on the interviewer’s questions.

The liar may also have additional pauses during their answers as they search for and test each word and sentence against what they have said previously or what they may have to say in the future. These pauses during the sentences may cause repeats of words, such as “I … I … I guess then we went to … ” or simply a slowing of the words as they become more careful in their selection of them. The voice around these pauses becomes garbled, soft, or trails away as the person speaks about an area of concern.

Observation Trumps Chance when Detecting Lies

Having a conversation with a deceiver is an especially difficult communication model. The interviewer who is able to observe changes in the voice, the pattern of speech, and the body can identify areas of concern where the deceiver fears their lies could be detected. By identifying these areas in loss prevention investigations, the interviewer can explore them in detail to determine if it is deception or an unrelated issue causing the changes.

Unfortunately, it’s unlikely that there will ever be a single or group of behaviors identified that an interviewer can use with high reliability to identify a lie. It is much more likely that the interviewer will be able to identify a subject’s concerns about a topic, word, or question that will require additional probing to ascertain its real meaning. If the individual is already concerned about a particular topic or point in their alibi, the interviewer’s probing of that area should increase the cognitive load and fear of detection, thus increasing the leakage of behavioral clues for evaluation.

“A Lie, Is It? Or Isn’t It?” was originally published in LP Magazine Europe in 2016 and updated May 8, 2017.


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