Lie detectors and neurononsense

Posted by on Oct 3, 2008 in Uncategorized | 2 Comments


When I got home last night, I flicked open this week's New Scientist to find this stinging rebuke of Cephos, the Massachusetts firm trying to persuade US courts to adopt their fMRI technology as a lie-detector.

I've tried to edit it down but it's worth reading the bulk of it. Just keep asking yourself – how would this critique relate to the use of neuroscience in marketing?

Put simply: if proper neuroscience isn't comfortable with diagnosing this relatively simple question of lying in legal testimony, then how can we hope to use the same technology with any confidence for the much broader range of stuff we're interested in and make the predictions we want to extrapolate from these measurements with any assurance?

OK here goes:

"You will not find many neuroscientists celebrating…[at the proposal the fMRI scans be used as admissible lie-detector evidence in US courts]. Despite the
company's optimism, the ability of fMRI to detect deception is far from
proven. In particular, the technology has not been properly tested in
real-world situations, where different kinds of lies and the diverse
contexts in which they are told may elicit different brain responses.
Does the principle behind the test – that certain parts of the brain
work harder when a person is lying – apply in every case?

don't know the answer because those studies that have been done on fMRI
and deception have not yet been replicated. More research – and
regulation – are badly needed….

the technology is eventually deemed reliable enough for the courts will
ultimately be decided by the judges. Let's hope they are wise enough
not to be seduced by a machine that claims to determine truthfulness at
the flick of a switch.

should also be sceptical of the growing tendency to try to reduce all
human traits and behaviours to the level of brain activity. Often they
do not map that easily. People engaged in demanding tasks have a
tendency to show activity in a small region of the lateral frontal
cortex, for example, but it is a far cry from there to declaring a
neural signature for intelligence.
Moreover, understanding the brain is not the same as understanding the
mind: some researchers suggest that thoughts cannot properly be seen as
purely "internal", but make sense only with reference to the thinker's
external world.

while there may be insights to be gained from matching behaviour to
brain activity, they will not necessarily lead to justice in a court of
law. The difficulty of linking particular neural structures with
specific behaviour hasn't prevented lawyers from using fMRI as evidence
that violent criminals have frontal lobe damage, though many
neuroscientists are uneasy about this.

Similar problems surround the use of fMRI to spot deception, at least until it has been rigorously tested….

….The history of the legal system is littered with stories of
technologies co-opted by lawyers before being properly tested. Let's
not make the same mistake again.

Time to put the light sabres away, methinks.


  1. Stan Lee
    October 3, 2008

    Interesting post. But not as interesting as the photo. The guy in the chair has the strangest look on his face.

  2. Mark
    October 3, 2008

    Thanks, Stan