14 September 2012

Do Lie Detectors Lie? And If They Do, Why Do We Love Them?

Photo credit: Limestone Technologies Inc., Creative Commons License
In the Simpsons (Fox Broadcasting Company) episode "Who Shot Mr. Burns", Moe (the bartender of the show) is administered a lie detector test which actually works:

Officer: Do you hold a grudge against Mr. Montgomery Burns?

Moe: No!

(Lie detector buzzes, red light flashes)

Moe: I didn't shoot him
(Lie detector dings, green light flashes)

Lie Detector Operator: Checks out, sir. You're ok sir, you're free to go.

Moe: Good, cause I got a hot date tonight.
(Lie detector buzzes, red light flashes)

Moe: A date.
(Lie detector buzzes, red light flashes)

Moe: Dinner with friends.
(Lie detector buzzes, red light flashes)

Moe: Dinner alone.
(Lie detector buzzes, red light flashes)

Moe: Watching TV alone.
(Lie detector buzzes, red light flashes)

Moe: All right! I'm gonna sit at home and ogle the ladies in the Victoria's Secret catalog!
(Lie detector buzzes, red light flashes)

Moe: Sears catalog.
(Lie detector dings, green light flashes)

Moe: Would you unhook this already, please?! I don't deserve this kind of shabby treatment!
(Lie detector buzzes, red light flashes)

The reality of lie detector (also known as polygraph) accuracy is starkly different. Even though they've been around for close to a hundred years, proper science has never proved their accuracy. But their fans continue to make use of them in the firm belief that they are in fact accurate.

Over 35 years ago, Justice Donald Morand in The Report of the Royal Commission into Metropolitan Toronto Police Practices (Toronto: Queen's Printer, 1976) wrote:
The polygraph examiners had many opportunities to answer the problems and criticisms suggested by psychiatrists and physiologists. Unfortunately, their response was invariable that the criticisms were not valid because, in their expeirence, the test worked. I have come to the conclusion that I must accept the evidecne of the psychiatrists and physiologists, which is consistent with both my common sense and my personal experiences, that all indviduals do not react in identical ways in a given situation.
Over 25 years later, the Supreme Court of Canada wrote in R. v. Oickle, [2002] 2 S.C.R. 3 at para. 95: 
I agree that the police exaggerated the accuracy of the polygraph. As many sources have demonstrated, polygraphs are far from infallible: see, e.g., D. T. Lykken, A Tremor in the Blood: Uses and Abuses of the Lie Detector (1998); J. J. Furedy, “The ‘control’ question ‘test’ (CQT) polygrapher’s dilemma: logico-ethical considerations for psychophysiological practitioners and researchers” (1993), 15 Int. J. Psychophysiology 263; C. J. Patrick and W. G. Iacono, “Validity of the Control Question Polygraph Test: The Problem of Sampling Bias” (1991), 76 J. App. Psych. 229. Similarly, this Court recognized in R. v. Béland, [1987] 2 S.C.R. 398, that the results of polygraph examinations are sufficiently unreliable that they cannot be admitted in court.
Academic authors have gone further, with some calling polygrahs "a dangerous erosion in our system of justice and democracy," others who "affirm the polygraph's ineffectiveness, and one who "compares control question testing to the reading of tea leaves" (see R.J. Marin, Admissibility of Statements, 9th ed (Aurora: Canada Law Book) at paras. 9.369-9.371 for a summary of opinions). 

Personally, I don't rule out the possibility of future technology achieving a deception detection accuracy of better than chance - voice tremor analysis and infrared facial heat measurement being two promising fields - but there needs to be independent, verifiable and scientific confirmation of results. 

So why do we love these machines that go beep if they really don't work? 

First, because of wishful thinking. The "wow, wouldn't it be great if science could solve all our human problems, including the problem of human deception" kind of thinking. 

Second, because of some of the people who are so convinced that they work are in fact those who submit to taking the test. Thus, if they think they can't beat the machine, they tell corporate employers, government security screeners, or the police the truth, the whole truth and nothing but the truth. In this sense, polygraphs can be a useful questioning tool - though this effective coercion of the truth is another reason courts exclude their results from evidence.

In applying for some jobs, you might not be given any choice but to submit to a lie detector test.  Take some solace in the fact that whether you pass with flying colours, or flunk out, may have little to do with whether you told the truth.

However, when you do have a choice over submitting to a polygraph, don't be drawn in by the "well, if you're telling the truth, you've got nothing to fear" argument. The truth won't necessarily stop that electronic box buzzing its disapproval with a blinking red light. 


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