To my knowledge traditional lie detectors don't really detect lies but rather blood pressure, pulse, etc. and can be fooled with sufficient self control.

What about Functional MRI? Can FMRI be used to develop a definitive lie detector? Is there a part of the brain which is active when telling lies versus the truth? and does this work cross-culturally?

  • Using your reasoning, an FMRI just detects brain activity (well, not even that, just blood flow). It can't definitively tell if you're lying. – Nick T Mar 16 '11 at 2:51

Currently the jury is still out on this technique. Getting an fMRI admitted in court has not met with great success, mostly due to the immaturity of the technology, as well as the cumbersome equipment needed to perform the scan. Dr. Sam Harris thinks that this technology may become more reliable in the future. However, many advances still need to be made in the technology, as well as understanding the human brain.

Dr. Paul Ekman is also doing a lot of work in this field. I see we had a good chat session on this (thank you anthony137 for reminding me of this).

  • With an fMRI you'd still have to get a baseline first, so couldn't you simply lie "in your head" while speaking the truth to skew the results? And what about false positives? When you first think about lying or holding something back, but then decide to tell the truth, the "deception" area of your brain would still light up. How would you distinguish "thinking about lying" from "actual lying"? – Oliver_C Mar 15 '11 at 10:18
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    Actually, there are specific areas of the brain that are only active when speaking a lie (a known untruth). Of course, withholding hasn't been researched as much yet, although this is still new technology, so a lot more work needs to be done. We didn't have 747s in the 1920s. – Larian LeQuella Mar 15 '11 at 22:14
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    the jury is still out I see what you did there! :D – JasonR Nov 22 '11 at 20:23

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