The History of … Polygraphs

Recent news has brought polygraphs into the spotlight.  What is their history?  How effective are they?  Let’s find out.

Throughout time people have tried to come up with ways to determine if someone is telling the truth.  For example, the Hindus used a rice test.  A person suspected of lying had to chew dried rice and spit it out onto a leaf from a sacred tree.  If they were able to do this they were telling the truth.  The idea was that you would have less saliva in your mouth if you were nervous about a lie.  In medieval Europe trial by combat was a way of figuring out who was telling the truth.  Parties in a dispute would fight out their differences.  The person who won was considered to be in the right.

Starting in the late 1800’s criminologists, scientists and psychologists began working on the ideas of first measuring blood pressure to determine if someone was being truthful and then of measuring breathing.  If blood pressure went up significantly or if breathing was more erratic a person was probably stressed out because they were lying.  William Marston, a scientist and psychologist, worked on one of these early versions of a lie detector but he had greater success creating Wonder Woman who coincidentally had a lasso of truth.

In 1921 John Larson, a medical student who worked on the side as a Berkeley, California policeman, invented what he called a polygraph (from Greek meaning “many writings” because of the lines produced).  His machine measured blood pressure, heart rate and respiration and recorded them as different lines on a piece of paper.

The modern polygraph was invented in 1926 by another Berkeley police officer named Leonard Keeler who improved on Larson’s design.  He added a component that measured how well an interviewee’s skin conducts electricity, i.e. are they sweating because they are uneasy about lying.

Like rice and combat the modern polygraph is controversial because of differing views of its effectiveness.  One of the most successful ways it is used is to prompt a confession before the actual test is even administered.  If a person believes the polygraph will work they are convinced they will be caught and confess.

Polygraph results from testing are not 100% accurate.  Estimates of their effectiveness are anywhere from 70% to 90%.  Their precision heavily depends on how good the administrator of the test is.  As a result, early on in their use, in a case called Frye v. United States, polygraph tests were prohibited from being used in court.  Polygraphs are currently used to test certain government employees such as those in intelligence and federal law enforcement.  However, people can “beat” a polygraph by causing themselves pain during the pre-test when the tester asks questions to get a baseline for what a lie looks like on the test paper for that individual.  Another way to pass a polygraph is by daydreaming to calm your nerves.  Soviet spy Aldrich Ames was able to pass repeated polygraphs when he worked for the Central Intelligence Agency.