For some reason I'm not sure about, this post, which originally appeared on Poe's Deadly Daughters in September 2011, has been used in two textbooks published by Pearson, and now I've received a request for its use in a third. Since few people read it the first time around, I thought it might find some new readers here.
Do you think you’re pretty good at spotting a liar?
Sorry, but I’ll bet you’re not as sharp as you think you are.
Researchers have found
that most people have a dismally low success rate, even in a lab setting
where they know for certain that some of those they’re studying are
lying. If we’re especially vigilant, we might spot half of all lies –
which means we’ll miss half. Police officers aren’t much better than the
rest of us, although they improve with experience. Those super-cops who
can always detect a lie, like the fictional Special Agent Gibbs on the
TV show NCIS, do exist in reality, but they’re extremely rare and psychologists have yet to determine how they do it.
Since the detective’s
ability to spot lies is crucial to crime-solving, some scientists are
finding ways to teach the skill to cops. Scientific American Mind
magazine’s September/October issue reports on experiments conducted by
one of them, social psychologist Aldert Vrij of the University of
Portsmouth in England. Vrij’s work is based on the human mind’s
inability to think along multiple tracks simultaneously. Lying is more
demanding than simply telling the truth, so if the interrogator gives
the suspect’s mind too much to process at one time, the person being
questioned is likely to slip up if he’s trying to sell a phony story.
Here’s the premise: The
liar has to worry about keeping his story consistent and believable,
first of all – which means suppressing all thought of the truth so it
doesn’t inadvertently slip out – but he also has to “look honest” by
controlling his expression and body movements. And he’s constantly
monitoring the cop’s reaction to what he’s saying. All that is
exhausting, and if the interrogator adds even a little more pressure,
that may be enough to trip up a liar.
Vrij and his colleagues have found several useful strategies for applying that extra pressure.
First, discount sweating and general nervousness. Even an honest person will be nervous under police scrutiny.
One way to trip up a liar
is to ask the suspect to tell his or her story backward, beginning at
the end. Devising a false story and keeping it straight is hard enough
without the burden of having to recount phony events in reverse. In lab
tests, this greatly increased mistakes and the likelihood of catching a
Interrogators can also
rattle a suspect by insisting that he maintain eye contact. Liars have
trouble concentrating on their stories if they’re looking directly into
the eyes of the people they’re lying to.
Asking suspects to draw
pictures of what they’re describing can also reveal the liars. Their
pictures will show fewer details than those drawn by truth-tellers, and
often the pictures won’t be consistent with verbal descriptions.
These easy techniques
have proven highly effective in the lab and should help police in the
real world do their work more efficiently. Best of all, they’re simple
enough to be used by fictional cops who aren’t endowed with the special
mental powers of Special Agent Gibbs.