Page 54 - BBC Focus - August 2017

CRIME

LIAR,

LIAR,

BRAIN’S

ON FIRE

Can brain scans

reveal when
someone is fibbing?

Since 2000, neuroscientists have
been investigating whether fMRI
Brain analysis using fMRI
(functional magnetic resonance scanners can help spot
imaging) brain scanners could when someone is fibbing
make the ultimate lie detectors.
fMRI works by measuring blood
flow of blood in the brain – the psychologist at Stanford
harder a specific region is working, University. “Is an instructed lie in a “MANY NEUROSCIENTISTS
the greater the blood flow to it. low stakes situation about a
Research on fMRI and lie detection meaningless event the same as a ARE SCEPTICAL OF FMRI’S
involves popping a bunch of person choosing to lie about
volunteers into a scanner and something they observed or an act
inviting them to tell porky pies. In they committed which, if caught, ABILITY TO DETECT LIES.
some instances, researchers have could see them paying a significant
found the tests to be 100 per cent fine or going to jail?” he says. FOR ONE THING, THE TEST
accurate, with brain regions such as Such concerns haven’t stopped
the ventrolateral and medial US lawyers trying to get fMRI SEEMS EASY TO BEAT”
prefrontal cortices springing into evidence admitted in court to
life and giving away the deception. prove that their client is telling the
And in one study, published in the truth. Judges have refused the
Journal Of Clinical Psychiatry in requests – so far. “Sooner or later,
2016, fMRI was 24 per cent more there will be a judge who will
likely to spot fibs than a traditional decide to go against the
polygraph test. mainstream and allow this,” says
But many neuroscientists are Dr Daniel Langleben at the
sceptical of fMRI’s ability to detect University of Pennsylvania. “It will
lies. For one thing, the test seems be a precedent and there will be
easy to beat. In a piece of research, another case, and another one,
Harvard students were asked to lie then there will be a free-for-all. It’s
while they were in an fMRI not a good outcome.”
machine. The accuracy of the tests Langleben argues that it would PHOTOS: SCIENCE PHOTO LIBRARY X2 ILLUSTRATION: VLADO KRIZAN
slumped to 33 per cent when the be better to conduct a large trial of
lying students wiggled their fingers fMRI lie detection to shine a light on
and toes. issues such as how sensitive the
Designing a test that’s realistic is technique is to attempted trickery,
tricky, too – something that such as a criminal wiggling their
worries Dr Anthony Wagner, a fingers and toes.

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