Practising the Fake Smile

As we've said, most people can't consciously differentiate
between a fake smile and a real one, and most of us are
content if someone is simply smiling at us — regardless of
whether it's real or false. Because smiling is such a disarming
gesture, most people wrongly assume that it's a favourite of
liars. Research by Paul Ekman showed that when people deliberately
lie, most, especially men, smile less than they usually
do. Ekman believes this is because liars realise that most
people associate smiling with lying so they intentionally
decrease their smiles. A liar's smile comes more quickly than a
genuine smile and is held much longer, almost as if the liar is
wearing a mask.
A false smile often appears stronger on one side of the face than the other, as both sides of the brain attempt to make it
appear genuine. The half of the brain's cortex that specialises
in facial expressions is in the right hemisphere and sends
signals mainly to the left side of the body. As a result, false
facial emotions are more pronounced on the left side of the
face than the right. In a real smile, both brain hemispheres
instruct each side of the face to act with symmetry.

Smugglers Smile Less
We were commissioned by Australian Customs, in 1986, to
help create a programme to increase the number of seizures of
illegal contraband and drugs being smuggled into Australia-
Until that time, it had been assumed by law enforcement officers
that liars increased their frequency of smiling when they
were lying or under pressure. Our analysis of film of people
who were intentionally told to lie showed the opposite - when
the liars lied, they smiled less or not at all, regardless of
culture. People who were innocent and telling the truth
increased their smiling frequency when being honest. Because
smiling is rooted in submission, the innocent people were
attempting to appease their accusers while the professional
liars were reducing their smiles and other body signals. It's the