> JKC has noted that evolution has put a tremendous amount of effort into
> detecting and concealing lies, so a perfect truth machine is unlikely.
> I say exactly the opposite: Evolution has put so much effort into lies
> that there's probably a module of the brain devoted to lying (anyone
> know if someone's looked for it?), and thus it might be very easy to
> detect activity with an fMRI.
You could start with [scanning] notorious liars, as their "module", if it exists, should be bigger or otherwise more noticeable than that of "normal" people. Perhaps it could be manipulated too, so that the subject becomes (virtually) incapable of lying. This is certainly something worth further investigation.