fMRI Lie Detection: Good Reasons to be Skeptical

Can a brain scanner allow us to detect if someone is lying?

In the mid-2000s, a wave of articles were published in both neuroscientific and legal journals on a new application of a (relatively new) neuroimaging technique. Functional Magnetic Resonance Imaging or ‘fMRI’ is a technique which allows real time monitoring of blood flow and metabolism in the brain: a strong correlate for locating brain activity. It was (and is) a vital tool in identifying behaviours and perceptions within structures of the brain.

In the early days of ‘neuro hype‘ fMRI was promoted (at times ad naseumas a revolutionary tool that investigators and court rooms could one day use to detect if an offender is lying. Older techniques for lie detection, such as the polygraph, have proven to be woefully inadequate, provoking a need for a more scientifically sound method.

Unfortunately, the days of a scientifically robust lie detection method are not yet upon us, nor will they be for some time.

Among the many issues facing fMRI lie detection is the fact that the interpretation of fMRI images remains a persistent challenge for experts in the field. We still can’t measure ‘brain activity’ directly, instead researchers are limited to monitoring blood flow – which may be telling them something different altogether.

Moreover, studies which demonstrate the use of fMRI for lie detection have also been very mixed, forcing even proponents of the technique to question its reliability. 

Finally, fMRI readings for ‘deception’ are likely to vary dramatically across cultures, as existing studies have been limited to the classic outliers of clinical research – educated, Western, university students.

Overall, there is very little to suggest that fMRI lie detection is a viable forensic tool, at least at this stage. Nevertheless, improvements in fMRI interpretation and larger scale cross-cultural studies may change this position in the future.

For a discussion of the admissibility of fMRI lie detection evidence in Australia courts, check out this paper by Leanne Houston from University of Technology Sydney.


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