PSYCHOLOGISTS call them 鈥渨izards of deception鈥�: those rare individuals with a natural ability to tell with complete confidence whether someone is lying. For decades, researchers and law enforcement agencies have tried to build a machine that will do the same thing. Now claims it has succeeded, and that using fMRI brain scans it can determine with 97 per cent accuracy whether someone is speaking the truth. It hopes the technology will be cleared for use in a US courtroom by early next year (see 鈥淏rainscans prepare to enter the courtroom鈥�).
You will not find many neuroscientists celebrating. Despite the company鈥檚 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 鈥� that certain parts of the brain work harder when a person is lying 鈥� apply in every case?
We don鈥檛 know the answer because those studies that have been done on fMRI and deception have not yet been replicated. More research 鈥� and regulation 鈥� are badly needed. Initiatives such as the , which aims to establish criteria for reliable lie-detection technologies, and the for a regulatory scheme to license their commercial use, will be crucial.
Advertisement
Whether the technology is eventually deemed reliable enough for the courts will ultimately be decided by the judges. Let鈥檚 hope they are wise enough not to be seduced by a machine that claims to determine truthfulness at the flick of a switch.
They 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 (see 鈥淥uter limits of the brain鈥�). Moreover, understanding the brain is not the same as understanding the mind: some researchers suggest that thoughts cannot properly be seen as purely 鈥渋nternal鈥�, but make sense only with reference to the thinker鈥檚 external world (see 鈥淢indfields: The marvellous mystery of mind鈥�).
So 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鈥檛 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. And even if neuroscientists can be satisfied, privacy advocates may not be. If the technology makes it to the courtroom, how will that affect a defendant鈥檚 right not to incriminate themselves? Does the Fifth Amendment apply in a scanner?
The history of the legal system is littered with stories of technologies co-opted by lawyers before being properly tested. Let鈥檚 not make the same mistake again. A high-tech test for truthfulness sounds enticing, but committing someone to jail, or worse, on the strength of it is not something we should be contemplating any time soon.
鈥淭he legal system鈥檚 history is littered with technologies co-opted by lawyers before they were properly tested鈥�
The Human Brain 鈥� With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report.
