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September 11, 1998

SUMMARY

SELECTED VOICE STRESS ANALYSIS STUDIES

This volume is presented as background to an understanding of the basic physiological basis of Voice Stress Analysis and a look at a sample of the divergent studies conducted since at least 1971. The materials here cited are resident in the files of the International Society of Stress Analysts and also available at most technical libraries concerned with voice and stress analysis.

 Historically,  the voice stress analyzer, in the form of the Psychological Stress Evaluator (PSE),  had its genesis in operational requirements of the US Army Counter Intelligence Corps, Fort Holabird Maryland.  A Quality Material Developmental Document was drawn and processed,  however no action was taken by the army to develop this capability. Rather, three officers, upon retirement from the Army joined forces to develop  the PSE, in 1971.   They arranged  for it to be evaluated by the Walter Reed Army hospital.  Their  objective  was  to describe their technology in physiological terms. The voice and hearing specialists described the phenomenon as graphically portraying the "Lippold Physiological Tremor" (enclosure two) the inverse relation of vocal cord tension to level of stress.  The PSE thus  measured  stress-induced changes to the  "muscle micro-tremor,"  as displayed in involuntary changes in the voice.

 Also in 1971, perhaps as a product of the Army requirement document, the US Army Land Warfare Laboratory, Aberdeen Proving Ground, Maryland contracted with Decision Control Incorporated , (enclosure three)"…to assess the capability of a method of voice analysis to detect stress in the spoken response, "NO. "  Tape recorded responses undergoing polygraph testing were  analyzed and compared to the polygraph interpretations. A good match in stress response assessment was obtained in this comparison.  A prototype voice analyzer was fabricated  and tested.  It processed recorded inputs and provided three voice measures.

 In 1976,  Dr. Jack Heisse, Jr., M.D., a Fellow of the International Society of Stress Analysts, conducted a study (enclosure four)  to validate and establish the reliability of the Psychological Stress Evaluator.  It was presented at the 1976 Carnahan House Conference on Crime Countermeasures, 5-7 May 1976 at the University of Kentucky.  The study concluded (1) " Audio Stress Analysis utilizing the PSE seems to be valid in detecting various psychophysiologic parameters in truth and deceptions so that a properly trained examiner, utilizing standard techniques, can evaluate these changes and thus utilize the instrument in truth and deception. " (2)  "The compliance between evaluators and the known results with 258 evaluation replies,  is 96.12 percent.

 In 1982,  the same Dr. Jack Heisse, Jr. M.D., a practicing otolaryngologist, reported on a study (enclosure  five) to compare the reliability of the Verimetrics Computer System as compared to the PSE, an instrument previously validated.  The study concluded that (1) individuals do show vocal change to emotions produced by colors as postulated by Luscher, and (2) Individual accuracy with six evaluators ranges from 87.5% to 94.6% accuracy.  The mean for the group is 91.67%.  Individual accuracy with one evaluator removed ranges from 91.1% to 94.6% for mean accuracy of 92.5%.  There is very little significant difference between  the two groups.  "… the Verimetrics computer has a far higher reliability than the PSE. "   1.

The Department of Defense Polygraph Institute (DODPI) conducted a series of studies,  testing the voice stress analysis instrument known as the CVSA, which were reported in 1995 and published in the POLYGRAPH, Journal of the  American Polygraph Association.  The tests were conducted with the product and philosophy of one commercial vendor without  consultation with any other authorities or agencies representative of the doctrine and  processes of voice stress analysis. 

 The first test (enclosure six)  having to do with technical and physiological theory of operation concluded that the CVSA instrument has been shown to detect discrete changes in speech fundamental frequency using laboratory instruments to simulate voice microtremor, confirming the CVSA's underlying theory of operation. The results did not confirm (1) existence of voice microtremor (2) relationship between microtremor amplitude  and psychological or physical levels of stress; (3) a reduction  of micro tremor amplitude during the act of deception; and (4) that voice micro tremor"--if it exists-- has sufficient  signal value to be detected by the CVSA.

 The second test, (enclosure seven) compared the traditional Polygraph and the CVSA, utilizing what is described as Peak of Tension (POT) tests.  It was found that the CVSA instrument and associated "processes" were significantly  less accurate than the polygraph instrument . 

Generally,  both tests are "reinventing the wheel"  and  seem not to be able to do as well as the inventor.  If you will recall  the PSE was evaluated by Walter Reed Army Hospital in 1971, where it was concluded that the PSE did  demonstrate the Lippold Micro tremor.  Also, in 1971,

As reported in enclosure Three to this summary, a study demonstrated  information not found by  DODPI researchers.. Also,  without detailing balances between polygraph and VSA techniques and methods,  the test structure used,  identified as Peak of Tension (POT),  is in fact the relevant-irrelevant test that was first used by Leonard Keeler,  the father of the polygraph, and is no longer considered valid.  Additionally, in the selection of irrelevant questions, ones were used that  may be in fact be relevant, leading to  false conclusions. The test also was conducted with the "absence of jeopardy" which  is an artificial constraint on the results of the analysis, being a measurable component in absentia.

Apparently, based on the  two foregoing studies, supported by preconditions and prejudices of the polygraph industry,  a Voice Stress Analysis Position Statement (enclosure eight)was published by the DODPI on September 11, 1996,  and immediately copied to APA journals and their web pages.  No effort was made to coordinate either of the on-going studies, nor their conclusions with Voice Stress analysis authorities,  to include the International Society of Stress Analysts,  whose existence is made known in every research library in the world.  Nor,  was mention made of a third study , at enclosure Nine, entitled, "Comparison of Accuracy rates Between Detection of Deception Examinations Using the Polygraph and the Computer Voice Stress Analyzer in a mock Crime Scenario." This study, (enclosure nine) with a report date of August 1996, reported that the accuracy and consensus of decisions rendered between examinations administered using the traditional polygraph instrument and the Computer Voice Stress Analyzer,  after detailing the protocols of the test, concluded that neither group of blind scorers achieved overall accuracy rates better than chance levels." 

Here the folly again of attempting to measure one Deception Detection system with the other.  The State of Virginia conducted a similar study,  with similar conclusions,  however,  the results were published without validation as a policy paper to the legislature.

And, at enclosure ten,  dated, but still  an accurate and thought provoking piece with a significant amount of information and powerful message.