How we change what others think, feel, believe and do
Four Factors in Facial Expression
When reviewing facial expressions there are four factors you can use, particularly when considering the possibility that the person is telling lies.
The shape of the facial expression is different when emotion is felt as compared with when the expression is faked.
Darwin described the 'inhibition hypothesis' where emotions involuntarily leak out. Similarly, Duchenne identified a genuine smile as using the orbicularis oculi muscle around the eyes which cannot easily be consciously manipulated.
We do not normally hold some facial expressions for long periods and natural expressions (notably smiles) have definable durations, typically between about half a second and four seconds. When people fake expressions they seldom get the timing right, typically holding the expression for too long.
Paul Ekman has also identified 'micro-expressions' as very brief flashes that betray inner feelings, such as when the corners of the mouth momentarily turn down in showing disgust. Most people miss this although recognizing these short displays is a learnable skill.
It has been noted that faked emotional displays can be asymmetrical, with emotional components being displayed more intensely on the left side of the face (although brain hemisphere dominance could possibly reverse this), whilst spontaneous emotional displays are more symmetrical.
When people tell the truth, their whole speech and non-verbal language are cohesive, each agreeing with the other.
When language is that which is not normally used, it can indicate lying. This includes hesitations, changes in emphasis, speech errors and indirect or distancing language (eg. Bill Clinton's 'that woman' remark). Other indicators include slips of the tongue, implausible statements, contradictions between what is said at different times and statements that contradict known facts.
There may also be misalignment between words, tone and body language, such as gestural slips, which are physical equivalents of speech errors and indicate internal conflicting thoughts.
So use these four areas as guides when watching the other person, particularly in their facial expressions as well as their speech and broader body language.
Ekman, P. and O'Sullivan, M. (2006). From Flawed Self-Assessment to Blatant Whoppers: The Utility of Voluntary and Involuntary Behavior in Detecting Deception, Behavioral Sciences & the Law, 24, 673–686