Prof. Ian Maynard Begg

Ian Maynard Begg, Professor, Department of Psychology, McMaster University, Hamilton, Ontario, Canada

Ian Begg, now a Professor Emeritus at McMaster University in Ontario, Canada, where he was part of the psychology department, wrote to the Witch Hunt Forum: "Polygraphs are recordings of changes in skin conductance/resistance when certain questions are asked, compared to a baseline when other questions are asked.If the change is big enough, the polygrapher might signal the response "deceptive."The basic theory underlying the use of polygraphs is that whenever a person lies, there are physiological changes in the body.Even if the theory is right, in which case the machine could detect intentional lies, honestly mistaken answers are not lies.Even at its best, the machine cannot detect departures from external truths; we need a time machine for that. . . ."

"Polygraphs are not lie detectors, and amytal is not truth serum.
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(Since Professor Begg retired in 1998, he has been completing the licensure (articles and bar admissions) for criminal law, working in the real world defending real people charged with crimes.)

Most people don't understand that a polygraph is only a machine that reads physiological responses, such as heart rate, body sweat, and is not a device that miraculously "knows" when someone lies.Poor responses can occur for many reasons.Some people can trick the machine, polygraph results are subject to operator error, and people respond to stress in many different ways.Law officers have been known to trick suspects by using a mimeograph machine that ejects a paper with the report that the suspect is lying.Usually the accused is asked to come down to the local police department and submit to polygraph.The person who is ignorant about polygraphs will often eagerly go to the st ation and let himself be hooked up to the machine believing he'll pass.

Ian Maynard Begg, Professor Department of Psychology, McMaster University