There is a false belief that polygraphs (the so-called ‘lie detectors’) can detect if someone is lying. Quite wrongly, the press have often called for its use whenever they need to see if a politician is lying or not.
There was a frequent call for its use in the Monica Lewinsky saga,for example. Take a look here:
Basically, medical personnel will tell you that when someone’s under stress, the body develops a ‘flight or fight’ reaction which causes the heart-rate to rise, blood pressure to climb, breathing to accelerate and palms to sweat. The polygraph assumes that psychology drives physiology and attempts to measure the above changes when a person is lying. Hence, it was thought that investigators could tell if a person was lying if the response to the above changes were excessive.
But criminals and even terrorists have gotten wiser : they would train controlling their body response at all times to questioning and even resort to tongue-biting and anal-tightening exercises to artificially create changes in body response. So much so, law enforcement agencies now consider these lie-detectors as “useless” nowadays.
Detecting when someone is lying also becomes difficult with pathological liars. As a medical student, we were taught that this was not a clinical diagnosis. You cannot find it in the ICD classification of diseases. A pathological liar can be defined as someone who often embellishes his or her stories in a way that he or she believes will impress people, often to the extent that they will believe in their own (false) story.
Here are some ways to tell someone is a pathological liar (contributed by WikiAnswers)
- They lie about even the smallest things. For example, saying “I brushed my teeth today,” when they didn’t.
- They add exaggerations to every sentence.
- They change their story all the time – fools people at first but once they get to know him/her, no one believes anything they ever say.
- They act very defensively when you question their statements.
- They believe what they say is true, when everyone else knows it isn’t.
- They tend to be extremely manipulative and may have a personality disorder.
Doctor2008's Weblog 
Hey doc. I do believe in what is written here. Moreso, mixed signals can be created.
However doc. , based on your knowledge, is there a possibility to recognise or identify or making onself aware about other human intentions ( not through lie detector though), perhaps, the simplest term is through “mind reading” and is there any method that can be done to diagnose whether the “mind reading” capability is accurate.
Thanks !
Thanks for reading.
“mind-reading”? I’m afraid we doctors are trained on matters based on scientific evidence. Having said that, we are all mind-readers to a certain extent in our daily social interactions.But, as to whether they are accurate, that’s difficult to prove scientifically.
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Thanks doc. I do hope that your reply could add more to my existing knowledge.
I am now in a lab called cognitive system science. Though I am not involved much with this type of research, but I found it quite interesting.
Do notice many equipments in the lab. such as sensors for movement of eyes, movement of head, movement of legs, body heat, shift of weight on seat and etc. The aim is to come with scientific evidence to prove hypothesis through statistical analysis.
Regardless of this, since I was 19, I notice that some people could read mind without using these sensors.
The behavioral traits of those who have this capability ? A friend indulge himself in a room with lights completely switched off for hours and he read the thoughts of people around him. Other’s simply bow , look to the ground or table, in deep thoughts and utter the thoughts of others.
From my reading, apart from God bestowed capabilities and non-invasive sensors, invasive methods are used by big organisation such as CIA, KGB and FBI, not to mention other organisations that seek these sort of capability. One of technic is microwave. These are people are sick for influence, control and power. Sigh.
That’s all my simple thought.