Doubting lie detectors and blushing beauties

Today’s New Scientist has an interesting follow-up letter to a recent article on whether brain scan lie-detection could ever be reliable court evidence. The article noted that the traditional and flawed lie polygraph lie-detector test had been questioned in the past, and the letter notes an earlier example of the test being criticised in an insightful short story:

Doubts about the use of polygraphs have been around for much longer than you report (4 October, p 8). In G. K. Chesterton’s Father Brown story The Mistake of the Machine, published in 1914, a polygraph detects stress in a prisoner accused of murdering Lord Falconroy. The reason isn’t guilt: the prisoner is in fact Lord Falconroy, in disguise and anxious to stay undiscovered.

Chesterton wrote that polygraph scientists “must be as sentimental as a man who thinks a woman is in love with him if she blushes. That’s a test from the circulation of the blood, discovered by the immortal Harvey; and a jolly rotten test, too.”

If you’re not sure quite how unreliable polygraph lie-detector tests are, I recommend an earlier article on Mind Hacks that is worth reading solely for the story of the falsely convicted Floyd ‘Buzz’ Fay, who trained 20 fellow inmates to fool the lie detector test to help prove his innocence. All while behind bars.

You gotta respect that.

Link to letter.
Link to Mind Hacks on polygraph hacking.