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June 5, 2008

fMRI, Lie Detection, and Statistics

I'm blogging from the AALS Mid-Year Conference on Evidence in Cleveland, where I just moderated a discussion this morning on fMRI and Lie Detection featuring Steve Laken (Cephos Corp.) and Mike Pardo (Alabama).  Although the studies on fMRI lie detection have their limitations, the results so far are quite impressive, with accuracy rates in the 90% range.  One wonders how soon they will make their way into court, where admissibility questions loom large.  Even if the technology is in fact sufficiently reliable for Daubert (and what I saw this morning suggests that this is true), the inherent conservatism of the legal system, coupled with the bias against analogs to polygraphs, will make admissibility a tough hurdle for the technology.  (For more on the bias against mind-reading devices, see this Note written by my student Leo Kittay.)

One striking aspect of the various discussions on fMRI during and after the session was the focus that people had on mechanism.  Many people are concerned that researchers have not yet pinpointed specific areas of the brain associated with lying, or have not determined specific pathways for deception.  Often, they are similarly concerned that other brain activities may "light up" the same regions.  I'm skeptical, however, that these concerns really matter.  While it may be desirable and interesting to know the specific mechanisms associated with deception, we really don't need to make such discoveries to have a practically useful lie detection machine.  All that matters is that some model exists (here, presumably using brain scans) that can with reasonable accuracy separate liars from non-liars.  How the model does that is in many ways beside the point.  As Laken pointed out during the discussion, medical researchers often have little or idea about the specific mechanism for a drug's success, yet such a limitation never prevents us from using its therapeutic benefits as proven through statistical/epidemiological studies.


June 5, 2008 | Permalink


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Thank you for the article on the fMRI. I agree with you that all the details about how the technology works is not essential to it's credibility in it's current limited form of use. It just has to be consistant and scientifically valid based on what they do know. Scientists never have said they must know everything about a topic before they use what they do know. Take brain surgery for example. Even though doctors do not know everything about the brain and all its complexities they are able to do certain types of proceedures with very high success rates. The important thing is knowing the abilities and limitations of what is being done and not, in this example, ban brain surgery from patients who need it because the brain is not fully understood yet. To put this extreme limitation on the use of scientifically valid testing shows a greater response to caution and fear than to benefits and opportunity. Caution and opportunity need to be in balance, not one pitted against the other as enemies. That is how good science will move forward to the benifit of boths sides of an issue.

Posted by: Tom WIlson | Jun 6, 2008 6:37:37 AM

As someone familiar with the intricacies of neuroscience, I would urge extreme caution in endorsing a method which can "light up" an area of the brain in response to particular stimuli. It is a leap well beyond faith to presume that a 1:1 correspondence exists between brain activity and the combined variables of semantic and moral meaning.

The brain is far more complex than most people imagine. A similar miscalculation was made by computer scientists --- back to Norbert Weiner --- in believing that it would just be a matter of time before computers would be able to model the human brain and silicon would become superior to carbon based lifeforms. That was some 40 years ago, and what passes for AI is a far cry from what the brain can do, even if you isolate a single network such as audition, the complexity of the brain system is daunting and far from being a well-understood organ.

A fMRI picture may be persuasive in the same sense that mentioning "neuroscience" lends credibility to expert testimony, but it needs far more replication and falsifiability studies before even contemplating its use as forensic evidence.

Posted by: Michael Urban | Aug 6, 2008 11:01:58 AM

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