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The Ontario Skeptic, Volume 16, Number 3 (Fall 2003) pp.1, 6.
Lie detectors don’t work...
...that’s the truth!
Dr. John F. Furedy, professor of Psychology at U of T, explains some slides during
his lecture “The truth about lie detectors” at the August 8 OSSCI meeting.
by Eric McMillan
Want to find out what a potential employee, criminal suspect or prospective sonin-law is really like behind that friendly exterior? Simple! Just submit him or her to
either a polygraph test or a graphology analysis.
Or maybe not, according to speakers at the OSSCI meeting on August 8. Two
presenters exposed the pitfalls of using lie detectors and handwriting analysis
before an audience of about 45 people. John F. Furedy, professor of psychology
at the University of Toronto, is a well-known opponent of the use of the polygraph
(“lie detector”), his position being made clear in his chosen title for the
presentation to OSSCI: “The Truth about Lie Detectors: The Entrails- Reading
Parallel”.
A polygraph machine, he explained, measures a body’s autonomic responses
(reactions the person cannot control), such as skin resistance response, to
questions the subject is asked. In a typical examination, the responses to socalled control questions for which the examiner knows what the response should
be are recorded first and then the questions concerning the matter being
investigated are asked. By comparing the control questions responses to the
responses to the serious questions, the examiner supposedly can determine if
the subject is lying while answering the latter questions.
Prof. Furedy disputes the value of this procedure, known as the Control Question
Test (CQT).
“It is not a test at all in the sense that, say, an IQ test is a test,” he says.
The validity of IQ tests in determining intelligence may be controversial, but at
least they are scientifically based and use standardized procedures, so the
results found by one competent operator will be the same as those found by any
other, says Furedy.
However, the so-called control questions of the CQT are designed by the
individual examiner, based on discussions with the subject, and the entire
examination can vary greatly in length and subject matter. Much of the procedure
is often spent not trying to determine whether the subject is telling the truth but
trying to elicit a confession of guilt. As a result it cannot be called a scientific or
standardized test.
Even when administered by an “expert”, the polygraph fails to distinguish
between an anxious-but innocent person and an anxious-but guilty person, says
Furedy.
Despite this lack of scientific underpinning, the use of the polygraph has become
entrenched as an official procedure in employment screening and criminal
investigations. For this reason, Furedy compares it to the reading of entrails by
expert priests in ancient Rome, which was accepted by the leaders of Roman
society.
For the meeting’s second lecture, Tim A. Campbell, an OSSCI member,
discussed his work as a forensic document examiner at Ontario’s Centre of
Forensic Sciences. He began by explaining the difference between what he does
and graphology.
Campbell uses scientifically supported procedures to match samples of written
materials and detect forgeries. Proponents of graphology, popularly known as
“handwriting analysis”, purport to detect personality characteristics of individuals
from their writing. Graphology has no scientific support for its claims and has
proven unreliable in experiments. We will have more on this subject in a future
issue.