Detecting Deception: Non-Verbal Cues

There are a lot of books, and articles, that exist about how to detect deception through a person’s body language i.e. the non-verbal cues they exhibit when lying. Whilst the information given is usually physiologically correct, it is often presented in simplistic terms e.g. if somebody looks up when asked a question they are lying etc. There is a tendency for the eyes to roll upwards when somebody is thinking about how to answer a question, if it requires significant cognitive processing. This could indicate deception i.e. the person is considering whether to lie or not, and what details the lie should contain etc. however if the question is complex and/or the answer needs to be detailed, there is more than a good chance that a truthful person will also look up as the consider and process their answer; so lie detection through non-verbal cues is not as simple as looking at a set of signals – the content and context of the question has to be taken into account as well, and most people lack the training and expertise to be able to bring all of these things together, when trying to detect deception. However, sometimes the general demeanor of a person may indicate that they are engaged in deception, and these nonverbal cues can be easier to spot.

Perhaps one of the biggest issues in detecting deception through body language is that a base-line is required i.e. without knowing how a person acts and behaves when telling the truth, it’s extremely difficult to recognize when they’re lying. There’s also the issue that if we already believe that a person is lying, our confirmation biases, will interpret every movement they make as an indication of lying e.g. if they keep looking away when they talk, we will take this as a signal of deception, without realizing that this is what they do when they’re telling the truth; most experienced liars will know to make and maintain eye contact when they are lying, as they are aware that most people believe looking away is a signal of deception – it may even be that “good” liars will make more eye-contact than truth tellers etc. The importance of having that baseline is important to those who use polygraphs, which is why the first thing the operator does is to try and establish how the person being interviewed responds to truthful questions; as it is the physiological deviations from this base-line, which indicates deceit. If you were interviewing a baby-sitter or somebody you were looking to employ to look after your children, you could start the interview asking relatively benign and mundane questions (from a security perspective), and then lead up to “stressful” ones e.g. “Would you ever have any one over to the house when you are looking after the children?” and/or, “How do you deal with discipline issues when children misbehave?” etc. Having set a baseline, you could then see if their body-language changes when/as they answer these more “high cost” questions.

Perhaps the easiest body-language change to identify when somebody is engaged in deception is “freezing” i.e. they go from talking with their hands and making large gestures, to shutting down most of their movement, even going so far as to sit on their hands, or clasp them, in order to stop them moving. There is believed to be a correlation in the evolution of our hands, with that of our speech; that as our thumbs and fingers became more articulate, so did our language – our ability to communicate verbally is linked to our ability to gesture with our hands. A classic therapist’s trick, when a patient is getting emotional when they speak, is to get them to sit on their hands; the result is that their speech starts to slow down and getting somebody to slow down when talking is one of the tools for de-escalating a situation. When I used to work with collection agencies, I’d advise those who worked on the phones to ask people if they could slow down when talking, if they were ever met with an angry tirade/response; if the person did they would start to interact in a much calmer and more measured manner. When a liar starts freezing up, they are concerned that they may talk too much, and say something that they don’t want to e.g. they might disclose elements of the truth or create a narrative that extends beyond their control. By restricting their hand gestures, they are less likely to over-talk, and this means they have less details to keep track of and manage. If a person goes from talking freely, and expressively, using their hands, to clasping them or limiting their movement in some way – they have deviated from their truthful baseline. What should always be remembered though is that they could be stressed by the question or the change in conversation, for other reasons than deception e.g. because the question brings up a bad memory or trauma etc. and this is why it is important not to put undue significance on a single response to a question, whilst considering whether the verbal cues (talked about in last week’s article), support the person’s change in demeanor.

Detecting deception through physical cues, is interesting – and can be useful – but relying on them solely as a means of identifying whether a person is lying or not, is not advisable. This is especially true when we consider that people with anti-social/psychopathic personalities often give of different non-verbal cues; and as this section of the population actively seeks out opportunities to be deceptive, they may be the most common and significant liars we engage with. Statement analysis i.e. the content of what is said, if often more accurate at identifying deception, than how a person physically responds and behaves – especially if they can reduce their non-verbal cues to micro-expressions, which are difficult to detect in the moment – and so we should really look on the physical cues which may be present, as supporting the verbal cues which accompany deception.