Scrutinizing faces catches liars

Liars can control certain facial expressions when facing scrutiny, but they can't suppress them completely or every time.

Behavioural countermeasures are the strategies engaged by liars to deliberately control face or body behaviour to fool lie catchers.

Researchers randomly asked 60 people to either lie or be truthful to an interrogator about taking a pair of movie tickets from an envelope. While being interviewed, the participants were told to attempt behavioral countermeasures, or suppress certain facial expressions, such as raising their eyebrows or smiling.

Meanwhile, the participants were told they would be rewarded if they could convince the interrogator they were telling the truth. They also said anyone found to be lying would be punished. The interviews were taped so researchers could analyse the participants' facial expressions frame-by-frame. They found that although the liars could minimise their facial movements when under scrutiny, they were unable to suppress them all.

And, since the lower face (and smile in particular) is easier to control than the upper face, the researchers predicted that the subjects would more greatly reduce their rate of smiling, compared to their rate of brow movement, when requested to suppress these actions. One can reduce facial movements when trying to suppress them, but can't eliminate them completely.

It was also found that in instructing the participants to suppress one specific facial movement, all of their facial movements were reduced. This response is typically greater when a person is lying because being dishonest raises a person's cognitive load, inhibiting their ability to interact with others successfully and naturally.

Despite the findings, the majority of participants believed they effectively controlled their expressions during their interrogation. Also, the findings could have an impact in security settings.