In research published earlier this year but of interest today for a reason or two we can think of, boffins at the University at Buffalo looked at the difficulty people have in suppressing give-away facial contortions when uttering an untruth.
In a study entitled Executing Facial Control During Deception Situations," Mark Frank PhD, a professor of communication at the University at Buffalo, drew on two decades of experience studying the faces of people lying when in high-stakes situations.
Together with former graduate student Carolyn M. Hurley, PhD, Frank reports that although liars can reduce facial actions when under scrutiny, they can't suppress them all.
Their study examined whether subjects could suppress facial actions like eyebrow movements or smiles while telling lies. And it turns out that they can, but only to a degree and some give-away indicators often remain daubed on the faces of the liars.
The results are derived from frame-by-frame coding of facial movements filmed during interrogations in which participants, some lying, some telling the truth, were asked to suppress specific parts of facial expressions. Hurley and Frank found that these actions can be reduced, but not eliminated, and that instructions to the subjects to suppress one element of expression resulted in reduction of all facial movement, regardless of their implications for veracity.
Most of the 60 study participants said they thought that they had controlled all facial movement and had remained "poker faced" during the interrogation, but the evidence suggested otherwise.
"Behavioural countermeasures are the strategies engaged by liars to deliberately control face or body behaviour to fool lie catchers," the report states. "Until this study, research had not shown whether or not liars could suppress elements of their facial expression as a countermeasure.
It continues: "There is great significance in observing and interpreting nonverbal behaviour during an investigative interview, especially when the interviewee is trying to suppress certain expressions."
The study involved 33 female and 27 male undergraduate subjects who were introduced into a mock crime scenario in which they were randomly instructed to either take or not take a pair of movie tickets from an envelope. Those that took the tickets had to lie to cover up their "crime".
They were then interviewed about the "theft" of the tickets by an experienced interrogator who was not previously made aware of whether the subjects were lying or not. Participants were told they would be rewarded if they convinced the interrogator of their honesty and punished if not. All denied taking the tickets.
Some subjects has been additionally instructed to suppress upper facial activity, like raising their eyebrows, and lower facial activity, such as smiling.
"Although these facial movements are not necessarily guaranteed signs of deception," said Frank, "expression suppression - regardless of its validity as a clue to deception - is clearly one of the more popular strategies used by liars to fool others. What we didn't know was how well individuals can do this when they are lying or when they are telling the truth.
He added: "We correctly predicted that in interrogations in which deception is a possibility, individuals would be able to significantly reduce their rate and intensity of smiling and brow movements when requested to do so, but would be able to do so to a lesser degree when telling a lie.
"And, since the lower face (and smile in particular) is easier to control than the upper face, we predicted that our subjects would more greatly reduce their rate of smiling, compared to their rate of brow movement, when requested to suppress these actions, and that turned out to be the case as well. We can reduce facial movements when trying to suppress them but we can't eliminate them completely.
According to Frank: "the findings of this study have important implications for security settings."