"The polygraph, for example, which measures physiological changes such as blood pressure, respiration and skin conductivity, only achieves an accuracy level of

"The polygraph, for example, which measures physiological changes such as blood pressure, respiration and skin conductivity, only achieves an accuracy level of around 50%..." Where does that statistic come from? I've definitely read that polygraphs have over 90% success as long as you account for obvious "counter measures". Basically, the person administering the test can clearly see if you are pulling tricks to defeat it.