Lie Detector

How can you tell if a person lies? That is an interesting question. Can you tell from a person's behavior? If he avoids eye contact when talking to you or if his timing is off between emotions gestures/expressions and words when speaking to you he could be lying. Also, if the person rubs her eyes or touches her nose she could be lying. Then again her nose may just itch. You would have to look at multiple behaviors to get a more accurate reading. Also, it helps if you observe the person over a long period of time to look for lying patterns. You actually need a more independent way to detect a lie that has a low rate of chance.

How about polygraph tests? Polygraph tests only measure several physiological variables such as blood pressure, heart rate, respiration and skin conductivity. If you are nervous taking the test you can possibly fail the test. There is even web sites that will tell you how to beat a polygraph test. The unreliability of polygraph tests is why in some criminal trials it is not admissible even though police departments use them. Polygraph tests are better but not by much.

What we need a way to measure the lie where the person cannot beat the measuring device. What about just measuring physical reactions of the brain? It appears that there are physical manifestations in the brain when you lie and the functional magnetic resonance imaging (fMRI) brain scanner can measure it. There is no way a person can control the behavior of your brain--ie the communication among the neurons in your brain. Brain scientists are saying measuring these manifestations are pretty reliable.

Scanning a person's brain to see if she is lying would probably eventually do away with polygraph tests. Businesses, CIA, FBI and NSA could scan potential employee's brains to see if they are trustworthy. The police could scan suspects to see if they are guilty of a crime or not. It would even be possible to scan airline passengers' brains to see if they would harm passengers on the plain. The big obstacle to using the fMRI is the cost. That and the size of the fMRI. It's really big. Both would have to shrink to make it more affordable and convenient to use. Plus there are some criticisms of the fMRI. Still measuring brain patterns would still be more reliable than the polygraph test.

When telling if someone is lying regardless of the measuring device the measurer has to ask the right question. Asking a blind person from birth what color your eyes are is meaningless to the blind person. He cannot answer the question because color is meaningless to him. Also the person has to know he is telling a lie. If the person is psychotic or blacked out during a crime he might not know if he is lying or not. Here is a good question for a passenger boarding an airplane: "Are you intending to physically harm anyone on the plane you are boarding." This is a good question because word anyone also includes the crew and not just the passengers. If you said kill rather than physically harm then this might leave out anyone who is going to just injure the pilots of the plane inorder to hi-jack it.

When asking a yes-no question you have to be specific and avoid opinionated questions. You also have to ask questions that get the answers you want. That is don't ask the passenger if he is a terrorist (an opinionated question to the passenger) if you want to know if he is going to commit a crime (a factual question). He probably would not consider himself a terrorist. He could just be an unstable person. If a person refuses to answer the question or spins then he should definitely not be allowed on the plane.