DIGITAL VOICE STRESS ANALYZER (DVSA)

BAKER GROUP - STUDIES

STUDIES WHICH DIRECTLY RELATE TO BAKER-DVSA 

 EARLY VALIDATION STUDIES AND RELEVANT CURRENT CORRELATIONS

The first voice stress analyzer was developed in 1970.  The primary purpose of the Psychological Stress Evaluator™ (PSE™) was to provide a means for covert lie-detection. Other professionals utilized the technique in the fields of psychiatry, psychology, fear evaluations, pain evaluations, and emotional reaction. 

The developers reportedly conducted five validation studies: 

    The first from tape-recorded television series To Tell The Truth.  The words, “My name is.” were evaluated.   No comparison of “known truth” was possible, requiring interpretation of “absolute stress” patterns.  Of 75 subjects evaluated, 71 were correctly selected.  Success rate of 94.7%

 During the second study of traditional truth verification test protocols, YES and NO in addition to NARRATIVE answers were given to invited “lie”, no jeopardy tests.  This very low stress level study consisted of 24 tests with 180 evaluated answers.  22 tests were correctly analyzed for a success rate of 91%. 

A Chief Polygraph Examiner utilizing a polygraph and voice stress analyzer simultaneously performed the third study on actual criminal suspects.  This has become known as the “PolyStress™” technique a term coined by the DVSA©™ developer, Dr. E. Gary Baker, Ph.D.  Twenty-six cases containing 162 relevant elements have been corroborated by confession or investigation.  This was reported as “real-world”, high stress test situations in which, VSA evaluation provided correct results in all elements for a success rate of 100 %. 

The fourth study was structured to provide comparative stress reactions to emotion producing words and neutral words.  The test was for psychological applications rather than truth verification purposes.  Of 53 elements in seven tests, 52 were correctly identified as a word group, for a success rate of 98.4 percent. 

In a “field use” study of 5,579 simultaneous polygraph / VSA examinations the two instruments resulted in the same findings or conclusions in 5,037 cases or 99.84% correlation.  NOTE:  Dr. Baker has found similar correlations in his ongoing PolyStress™ examinations of Post-conviction  Sex Offender Testing. 

 1. Comparison Study of the Baker-DVSA, Lantern, and PSE.
Marvin McCorkle, President, International Society of Stress Analysis, August 2002.
Contact: MarvinMcCorkle@aol.com
Findings: “Derived stress patterns of the same-recorded utterances from the DVSA, Lantern, and PSE-101 are essentially the same.”
“Based on this comparison it is [our] opinion that any previous validation study conducted with the PSE and Lantern would also be applicable to the Baker-DVSA by ISSA.”

2. Study of the Field Use of the Psychological Stress Evaluator (PSE) (VSA), Anthony E. Dahm, Dektor Counterintelligence and Security, Inc. May 1974.
Findings : Simultaneous tests with polygraph and PSE (VSA). Of 5037 cases use of the two instruments resulted in the same findings. 99.84% correlation.
Percentage of examination findings confirmed:  Of 10,202 examinations conducted, 0 inaccuracies.
Number of subjects cleared of suspicion:  Of 3286 examinations the subject was cleared in 2264 cases for clearance of 68.9%.

3. The Psychological Stress Evaluator (PSE) (VSA), A Validation Study, Mi chael P. Kratz, Lt., Chief Polygraph Examiner, Howard County Police Department, MD, 1975.
Findings : There is a 100% inter-examiner reliability with PSE (VSA) compared to 93% with polygraph. This study’s finding of 100% corroboration between the results…and independent corroboration present a successful validation. The physiological change in the voice, which is detected by the PSE (VSA), is a valid indication of the stress interpreted… to detect attempted deception.
The PSE (VSA) is a valid component…either in tandem with the polygraph or used as a single instrumentation of stress.

4. A Validation and Reliability Study of the Psychological Stress Evaluator (PSE) (VSA). John W. Heisse, Jr. M.D., February 1976. Presented before the American Society for Industrial Security Annual Seminar – 1975 . Published in Security World – 1976, Presented at the 1976 Carnahan House Conference on Crime Countermeasures, May 1976.  (Dr. Baker participated in this study.)

Findings : Truth and deception is an art! Results found in the study indicate clearly that the frailty of the system is the human factor. The instrumentation appears to perform just as it was designed to perform.
Audio Stress Analysis seems to be valid in detecting various psychophysiological parameters in truth and deception so that a properly trained examiner utilizing standard techniques can evaluate these changes and thus utilize the instrument in truth and deception.
The compliance between evaluators and the known results with 258 evaluation replies is 96.12%. With examiners added to the group the reliability jumped to 96.78%.
It would appear that the validation study asked for in the article, The Psychological Stress Evaluator: A Recent Development in Lie Technology, and the validation found by Kratz and Dahm, and reported by Stanley and Kriete in their address to the International Society of Stress Analysts in Chicago in 1973 is authenticated by this study.

5. Air Force Research Laboratory, Rome, NY, October 2000. Funded by the National Institute of Justice, a three-year study by the AFRL determined that voice stress analysis achieved an accuracy rate of 100% when used to detect stress in 45 utterances in known-conclusion cases.  (Page 16, paragraph 6.5.3.5) http://www.ncjrs.org/pdffi les1/nij/193832.pdf

National Law Enforcement and Corrections Technology Center-N.E. / U. S. Air Force Research Laboratory / Law Enforcement Analysis Facility. Phase Two which included the Baker-DVSA has been completed but the complete report has not yet been released to the public.  The primary analyst conducting the Air Force Research Laboratory and Law Enforcement Analysis Facility VSA Phase Two Study has presented an overview paper entitled, “EVALUATION OF VOICE STRESS ANALYSIS TECHNOLOGY”

Dr. E. Gary Baker trained the AFRL / LEAF evaluators in VSA chart reading techniques, use of the DVSA, and Polygraph Psychophysiological Detection of Deception - Principles of Polygraph Chart Interpretation.   We therefore believe that this positive conclusion also validates the Baker techniques of chart interpretation and stress pattern quantification. 

CONCLUSION

Our results indicated that, given the VSA systems

tested, results indicate that this technology, with a trained

and experienced examiner is capable of detecting

deception or truthfulness in a subject at a rate better than

chance. The experience an examiner has with VSA

technology plays a key role in their ability to detect

deception.

These instruments alone are not “lie detectors”. The

decision as to whether a subject is being truthful or lying

should only be made by a trained examiner. This decision

should be based upon reviewing the data presented by the

instrument, the demeanor of the subject, and other

evidence from the case. VSA systems are capable of

providing an examiner with a waveform or other response

that may be a reasonable reflection of the stress level

being experienced by the subject, in a majority of the

cases. The correct interpretation of this indicator is the

responsibility of the examiner.

The goal in using a VSA system or polygraph should

be to convince the subject that they cannot deceive the

operator, and that the instrument will detect their

deception and their best avenue is to confess to the crime.

This study has shown that VSA systems will produce

results that trained operators can employ with confidence

to obtain confessions.  ( Ed: Emphasis added.)

The results of these examinations should not be

considered “proof positive” of innocence or guilt. While

some consider these tools as an aid in focusing an

investigation on proving someone guilty, officers should

not lose sight of other suspects or evidence that may

indicate otherwise.

This study has also shown that when training and

experience of an examiner are taken into consideration,

test results indicate that over time there is a marked

improvement in an examiners ability to correctly identify

deceptive subjects. Likewise, the comparison between

the two analysts of different skill levels also indicates that

experience may be a factor in improving accuracy.

Observations made during the study of other analysts

seems to indicate that the more opportunities one is given

to run tests, examine charts and receive feedback (ground

truth), the better the examiner becomes.

6. Ruiz, Legros, & Guell, 1990. Voice analysis to predict the psychological or physical state of a speaker. Published in Aviation, Space, and Environmental Medicine, 1990. Ruiz et al. reports that their “research suggests that psychological stress may be detected as acoustic modifications in the fundamental frequency of a speakers voice” and “that the fundamental frequency of the vocal signal is slowly modulated (8-14 Hz) during speech in an emotionally neutral situation. In situations demanding increased ‘mental or psychomotor’ activity, the 8-14 Hz modulation then decreases as the striated muscles surrounding the vocal cords contract in response to the arousal, thus limiting the natural trembling”

7. Chapman, J. Criminal Justice Department, Corning Community College, NY. “The Psychological Stress Evaluator As A Tool For Eliciting Confessions”, 1989. Chapman selected 211 criminal cases at random from 2,109 known-conclusion cases where voice stress analysis was used to test suspects. Professor Chapman’s study confirmed that voice stress analysis was accurate when utilized as a truth verification device and produced a confession rate of 94.8% of the cases where deception was indicated

8. Brockway, B.F., University of Colorado School of Nursing, Denver, Colorado. “Situational Stress and Temporal Changes In Self-Report and Vocal Measurements.” Presented to the annual meeting of the American Association For the Advancement of Science, February 1977. Brockway’s study reports that voice stress analysis does depict predictable and self-reported anxiety

9. Smith, G.A. “Voice Analysis For Measurement Of Anxiety.” British Journal of Medical Psychology, 1977. The author concludes that voice stress analysis is a valid measure of anxiety

10. Borgen, L.A., Goodman, L.I., Parke-Davis Research Laboratories, Ann Arbor, MI. “Voice Stress Analysis of Anxiolytic Drug Effects.” Results of the study indicated that voice stress analysis of the verbal responses correlated well with the other physiological responses to acute stress.

11. Inbar, G.F.., Eden, G. Dept. of Electrical Engineering Technion, Israel Institute of Technology, Haifa, Israel. “Psychological Stress Evaluators: EMG Correlation With Voice Tremor” published in Biology of Cybernetics, 1976. Inbar and Eden were able to independently verify the existence of the 8-14 Hertz ‘micro-tremor’ and to trace its origins to the central nervous system.

12. Wiggins, S.L., McCranie, M.L., and Bailey, P. Department of Psychiatry, Medical College of Georgia, Augusta, Georgia. “Assessment of Voice Stress In Children”. Published in the Journal of Nervous Mental Disorders, 1975. The authors concluded that “audio stress can be detected with a voice stress analyzer in psychiatric patients during the course of therapy and that the VSA could serve as a useful tool for this purpose”

13. Heisse, J. “Is The Micro-Tremor Usable? - The Micro-Muscle Tremor In The Voice.” U.S. House Subcommittee of the Committee on Government Operations, 1974. Heisse analyzed 91 known-conclusion criminal cases utilizing voice stress analysis and determined that “Audio stress analysis seems to be valid in detecting changes in various psycho physiological parameters so that a trained examiner utilizing standardized techniques can evaluate these changes and thus utilize the instrument in truth and deception”.

14. Brenner, M. “Stage Fright and Steven’s Law.” Dept. of Psychology, Ohio State University, presented at the convention of the Eastern Psychological Association, April 1974. Brenner, utilizing a voice stress analyzer, established that the frequency of vocal stress increased as a function of audience size. Abstract available from ISSA archives.

15. Lippold, O. “Oscillations In The Stretch Reflex Arc And The Origin Of The Rhythmical 8-12 C/S Component Of The Physiological Tremor.” The Journal Of Physiology, February 1970. Lippold first discovers the physiological tremor in the human voice in the 8-12 Hz range.

16. Lippold, O., Redfearn, J., Vuco, R. “The Rhythmical Activity Of Groups Of Muscle Units In The Voluntary Contraction Of Muscle.” The Journal Of Physiology, August 1957. Lippold, Redfearn and Vuco begin exploring the correlation between muscle activity and stress.

17.  U.S. NAVY STUDY - Voice Stress Analysis as a Measure of Operator Workload

Authors: Schiflett, S. G.; Loikith, G. J.; NAVAL AIR TEST CENTER PATUXENT RIVER MD

Abstract: This study attempted to determine if Voice Stress Analysis (VSA) could be used to detect the amount of situational stress in the voice while subjects performed a four-choice information processing task at different presentation rates. The 42 subjects were divided into group I - Jet, group II - Prop, and group III - Staff. A Response Analysis Tester (RATER) presented a four-choice discrimination task in which the subjects were required to match a response key to each of four stimuli appearing in a display window. The sequence of stimuli was randomly presented in an automatic-paced mode for nine 1-min tests. The stimuli presentation rates were set at one symbol per 1.5 sec, .75 sec, and .50 sec. At the end of each block of three tests, the subjects estimated self-performance as percent correct and rated stress on a scale of one (no stress) to seven (high stress). Voice signals were initially recorded on magnetic tape, then processed through filtering circuits and displayed on a strip chart for subsequent visual analysis and interpretation. A subjective scoring criterion was established and then translated into electronic equivalents and automated on a Varian 73 computer for voice pattern recognition analysis. Significant main effects for percent-correct responses were obtained for groups, presentation rate, and groups X presentation rate interaction. No significant differences were found in the correct responses of the subjects when the number was verbalized or not verbalized. The Staff group produced significantly fewer correct responses than either the Jet or Prop groups at the .75 sec rate. Voice stress analysis showed significant correlations with performance scores and stress ratings of a selected pool of subjects. Discussion includes the potential application of an objective, reliable, sensitive, and non-obtrusive measure of stress in vocal communication systems that require operator workload assessments.

18. US Department of Defense.  A survey of US law enforcement users of VSA,  conclusively demonstrates that the VSA is a useful tool.  March 30,  2007

19. Study of the Effects of Audio Corruption on Voice Stress Analyzer Results

Phase 1, Clifford S Hopkins, 2005.  Law Enforcement Analysis Facility,

National Law Enforcement and Corrections Technology Center –NE

While this study was not inclusive of all types of noise, it did begin to give us an understanding of how background noise can corrupt the voice signal being analyzed, what to look for and how to avoid having tests that are invalid due to noise corruption.

Using audio enhancement software it is possible to clean up corrupted audio and produce results similar to the original in both wave form and analyzed form.  There are some differences observed, but the process does appear to return the data to its original form.

Summary:

Noise can affect the results of energy based VSA systems with a noise level about -36 db being the point at which the responses become questionable.  While it is preferred to use as clean a sample as possible, in the energy based systems rehabilitation of the data may be possible.  Further studies will be conducted with other types of noise and with the frequency based VSA systems.

NOTE:  This study utilized the Baker-DVSA and the US Air Force Research Laboratory “Stressalyzer” in the research. 

It is clear that the majority of the survey respondents believe VSA is a useful tool.  Key factors in this usefulness appear to be its ease of use, timeliness, affordability, and ability to help convince guilty subjects to confess.  It appears to be very helpful in clearing cases.

 Anecdotal validations may be obtained from any user of the Baker-DVSA©™.

A comprehensive Law Enforcement user list is available upon request.