how effective are lie detectors?

[hedge]

How effective are lie detectors?

[andy-hughes]

It depends.

If someone believes what they say to be the truth, then they will pass a LD test, but that simply proves that they think what they say is true, it doesn't mean that they are speaking the truth.

If someone believes that the earth is flat, and they are asked that question in an LD test, the test will show that they speak the truth, even though what they say is not true.

So the answer is - it depends on the questions asked, and the beliefs of the person being tested.

[briar-rose]

Attach some of the people on here to one - the results'd have me laughing my socks off.

[Neilzulu1]

With no outside influences, ie alcohol. Around 96 %.

[dzug]

Their effectiveness depends in part on the subject believing they work.

They are not used in the legal system this country because they leave room for 'reasonable doubt' as to their accuracy.

[newtron]

My psychology professor said that they were not very accurate and the whole process of conducting a lie detector test was really based on intimidation to get the person to confess. Apparently, prior to asking the actual questions of concern, they need to ask you questions that they they know you will answer truthfully, such as "What is your name?". So if step on a tack (or do something similar ) while answering these preliminary questions, the weird results will probably make the whole test invalid. That was a recommendation by my psychology professor.