Polygraph tests have been proven internationally through extensive study to be no more effective than guessing whether an individual is truthful or not and can be beaten (reasonably) easy through physical techniques that trigger false positives and negatives. There's a good reason why police and other legal departments around the world (including here) do not make use of polygraphs and they are not considered evidence admissible in court, as their accuracy is spotty at best. This of course doesn't prevent 3rd parties from using polygraph tests (lets stop calling them lie detectors) against employees, and individuals to "weed out" potential dangers - which is bad news.
A polygraph test measures typical stress indicators such as elevated heart rate, breathing, increased skin conductivity (perspiration), etc. to determine whether someone is most likely lying or not. Unfortunately these are just STRESS indicators, not lie indicators (and painting them as such is just disingenuous) and the simple act of taking place in a polygraph test can trigger these responses despite telling the truth.
There are 2 things going on during a polygraph test that are the real "trick" to the system:
1) The false belief imprinted on a interviewee that the system they are partaking in is "lie detection" and that this magical machine will instantly know if they are telling the truth or not. This false belief can result in the interviewee ultimately giving away a lie without realising it.
2) The cold reading and observation being done by the interviewer is the real "lie detection" taking place. During the interview many experienced polygraph testers are using various observation skills to determine possible lies with the machine giving indication of whether there is any undue stress associated with a particular question.
Unfortunately, due to this, #2 amounts to a Q&A session, and without actual confession it's no more admissible than a police enquiry because the machine is NOT detecting lies, the interviewer is (and who knows how good that person is at actually spotting lies).
Polygraph testers such as Coen, while I'm sure having good intentions, have every reason to continue lying about the efficacy of polygraph testing and their accuracy in detection. Their whole premise revolves around keeping people believing that the "machine" is a magic lie detection box, because without that, other than some A+ observation skills, they're unlikely to come away with anything useful and they're all out of a job.
Now as for brain scan techniques, I would say those hold far more promise, though again it's going to be dependent on how they work. If they don't actually measure LIES, then they're going to be just as bad as polygraphs, perhaps even more-so because people are always quick to misrepresent anything about the brain as "fact" (violent video games cause the brain to light up under CT scans, so that means it's getting trained to kill. FACT!) when in "fact" it's still largely uncharted territory.
What this is doing on the front of MyBroadband is absolutely beyond me.
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