Aldert Vrij‘s Guideline to Catching Liars by Examining Verbal & Nonverbal Behaviour
– Observational Guidelines –
(1): Use flexible decision rules.
Research clearly demonstrates that there’s no one single behavioural or verbal cue relating to deception – there’s no Pinocchio’s nose. Different people show different cues (or clues) to deception in any given situation. Look for clusters (a group of 3 or more cues together, such as clearing the throat, folding the arms and leaning backwards when asked a question – when they hadn’t done it previously). So again, look for clusters outside of the person’s normal behaviour (or baseline behaviour) and avoid fixed decision rules (such as “liars look away” and other lying myths). It’s extremely important to obtain a baseline of the person – their normal behaviour – also called benchmarking.
(2): Clues to deceit are most likely to occur when liars experience emotions or cognitive load, or attempt to control themselves.
The act of lying itself doesn’t affect somebody’s nonverbal behaviour or speech – the liar must experience feelings of guilt (deception guilt) or fear (detection apprehension), or feel excited about the possibility of fooling someone (duping delight). In low-stake situations, lairs often don’t experience these emotions, making lie detection very difficult. In high-stake situations being disbelieved may have serious consequences for the liar, which makes it more likely that liars will experience emotions such as fear or guilt.
(3): Consider alternative explanations when interpreting cues of emotions, cognitive load, and attempted control.
Both liars and truth tellers are more likely to display signs of emotions, show signs of an increased cognitive load, and attempted behavioural control in high-stakes situations than low-stakes situations. For example a truthful person may fear being disbelieved (also referred to as the Othello Error).
(4): Be suspicious but do not show suspicion.
Overall people have the tendency to believe others. Sometimes this is due to a lack of interest in detecting a lies (the ostrich effect), or because of a variety of reasons related to the truth-bias. Perhaps because of the truth-bias, being suspicious is a necessary prerequisite to catching liars, which leads to improved analysis of nonverbal and verbal behaviour. However it’s important not to let on suspicion, as this may make truth tellers feel uncomfortable (which would result in the Othello error), or have liars close up and refuse to talk or they may change their behaviour to come across more credible.
(5): Don’t make up your mind too quickly about whether a person is lying.
Judging whether someone is lying isn’t straight forward, however once people have made up their mind whether someone is telling the truth or not they have a tendency to interpret additional information to support their decision (the confirmation bias). This is where lie detectors run the risk of failing to notice further important information – or misinterpreting the information in order to justify their decision – right or wrong.
(6): Pay attention to the more diagnostic verbal and nonverbal cues to deceit.
Don’t pay so much attention to subjective (believed) indicators; rather lie detectors should focus on objective (actual) indicators.
Subjective indicators (or lie myths). include inaccurate actions that are perceived as deceptive such as an increase in position shifts, fidgeting, eye blinks, pauses and decrease in gaze.
Objective indicators include more accurate actions (in clusters) that are more often shown by liars than truth tellers such as an increase in voice pitch and pause durations, and a decrease in illustrators.
Overall, beware of mythical “lie detection” constructs.
(7): Pay attention to nonverbal and verbal cues simultaneously.
This is harder than it sounds, which is why I personally recommend working in pairs for interviewing, with one person interviewing and the other observing. If two people aren’t available however, here are three approaches that can help.
i) Take into account a mixture of nonverbal and verbal cues, without looking at the relationship between to two sets of cues. This is more accurate than one or the other.
ii) Examine nonverbal behaviour in relation to speech content, mainly the differing types of speech illustrators made during speech.
iii) Examine mismatches between nonverbal behaviour and speech content – micro expressions, emotions and body language that contradict their statement.
(8): Pay attention to deviations from a person’s honest reactions in similar situations: the comparable truth.
Take into account personal differences when making judgments to avoid the Brokaw Hazard (the possibility of misjudging people’s idiosyncrasies as deceit). In other words, obtain a baseline under similar conditions where the truth was told in order to make an assessment of any behaviour that differs; the comparable truth. Be aware of the Othello Error (a truthful subject fearing being disbelieved) and take into account situational stressors.
(9): Employ indirect lie detection techniques.
Rather than answering the question; “Is this person lying?”, observers could attempt to answer a different question, such as; “Is this person having too think hard?” Research has shown that observers are better lie detectors when answering the latter indirect lie detection question then when answering the former direct lie detection question.