Antique Polygraph Sanborn Model 51, 1930's

Using an invention that measured an increase in systolic blood pressure, William M. Marston claimed he had a way to detect verbal deception in 1917. Then, in 1921, a University of California medical student by the name of John Larson developed a machine that measured pulse rate, blood pressure, and respiratory changes at the same time. Larson went on to develop what has become known as the R/I (relevant/irrelevant) procedure. The R/I method asked both relevant and irrelevant questions to get base line readings on a person. The above is a very early polograph machine from the 1930's. You can review other antique and rare polygraph machines at the below web site:

Polygraph Instrument History
Sponsored by Decker Instruments, this place has photos and descriptions of very old polygraph machines.

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