“Nothing But the Truth”

Xu Xiaomin writes about polygraphy in China for the English language Shanghai Star. Excerpt:

You can remain silent, or everything you say may be subjected to a lie detector test, whose value is still suspect.

Generally speaking, perspiration is easiest to control by individuals attempting to cheat the polygraph, but pulse, blood pressure and especially skin resistance are very difficult to master.

PICK a card, any card from four and do not reveal it to others. Next answer several questions in the affirmative or negative, and Lu Baoqing will tell you which card you are holding.

This is not magic or fortune telling. This is polygraph technology, according to Lu – a teacher from the detection department of the Shanghai Police.

“It is just a small trick,” Lu said. “Polygraph tests have much more important uses in detective work.”

This article provides information that suggests that Shanghai police make use of the Guilty Knowledge Test, which is theoretically sounder than the pseudoscientific “Control” Question “Test” widely used in the United States. But even the Guilty Knowledge Test has not been validated by peer-reviewed research and remains susceptible to countermeasures.

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