HNS Polygraph Services | Does Voice Stress Analysis actually work?

VSA software programs are designed to measure changes in voice patterns caused by the stress, or the physical effort, of trying to hide deceptive responses. VSA programs interpret changes in vocal patterns and allegedley indicate on a graph whether the subject is being "deceptive" or "truthful."

Various distributors of voice-stress analysis systems suggest that recent advances in the technology, such as layered voice-stress analysis, have elevated voice-stress lie detection to new levels of dependability and effectiveness. Some suggest that the dismal performance of voice-stress analysis lie detection in recent federal studies can be attributed to improper test conditions or to tests being conducted using outdated and inferior versions of the technology.

Still, while many governmental investigative, military and law enforcement agencies have expressed an eagerness to find a credible new means of lie detection, study after study has failed to yield strong scientific evidence in support of this technology. Over the last 30 years other researchers outside of the government have also researched voice stress for lie detection, and published their findings in scientific journals. The general conclusion has been that the accuracy is less than 50%.

Below is a list of the university-grade research studies that have investigated voice stress as a deception detection approach. Some studies looked at the Computer Voice Stress Analyzer device in particular, while others investigated whether voice stress analysis in general could be used to detect stress or deception. Copies of these studies can be obtained at many university libraries.

Brenner, M., Branscomb, H., & Schwartz, G. E. (1979). Psychological stress evaluator: Two tests of a vocal measure. Psychophysiology, 16(4), 351-357.
Conclusion: "Validity of the analysis for practical lie detection is questionable"

Cestaro, V.L. (1995). A Comparison Between Decision Accuracy Rates Obtained Using the Polygraph Instrument and the Computer Voice Stress Analyzer (CVSA) in the Absence of Jeopardy. (DoDPI95-R-0002). Fort McClellan, AL: Department of Defense Polygraph Institute.
Conclusion: Accuracy was not significantly greater than chance for the CVSA.

DoDPI Research Division Staff, Meyerhoff, J.L., Saviolakis, G.A., Koenig M.L., & Yourick, D.L. (In press). Physiological and Biochemical Measures of Stress Compared to Voice Stress Analysis Using the Computer Voice Stress Analyzer (CVSA). (DoDPI01-R-0001). Department of Defense Polygraph Institute.
Conclusion: Direct test of the CVSA against medical markers for stress (blood pressure, plasma ACTH, salivary cortisol) found that CVSA examiners could not detect known stress. This project was a collaborative effort with Walter Reed Army Institute of Research.

Fuller, B.F. (1984). Reliability and validity of an interval measure of vocal stress. Psychological Medicine, 14(1), 159-166
Conclusion: Validity of voice stress measures was poor.

Janniro, M. J., & Cestaro, V. L. (1996). Effectiveness of Detection of Deception Examinations Using the Computer Voice Stress Analyzer. (DoDPI95-P-0016). Fort McClellan, AL : Department of Defense Polygraph Institute.
DTIC AD Number A318986.
Conclusion: Chance-level detection of deception using the CVSA as a voice stress device.

Hollien, H., Geison, L., & Hicks, J. W., Jr. (1987). Voice stress analysis and lie detection. Journal of Forensic Sciences, 32(2), 405-418.
Conclusions: Chance-level detection of stress. Chance-level detection of lies.

Horvath, F. S. (1978). An experimental comparison of the psychological stress evaluator and the galvanic skin response in detection of deception. Journal of Applied Psychology, 63(3), 338-344.
Conclusion: Chance-level detection of deception.

Horvath, F. S. (1979). Effect of different motivational instructions on detection of deception with the psychological stress evaluator and the galvanic skin response. Journal of Applied Psychology, 64(3, June), 323-330.
Conclusion: Voice stress did not detect deception greater than chance.

Kubis, J. F. (1973). Comparison of Voice Analysis and Polygraph As Lie Detection Procedures. (Technical Report No. LWL-CR-03B70, Contract DAAD05-72-C-0217). Aberdeen Proving Ground, MD: U.S. Army Land Warfare Laboratory.
Conclusion: Chance-level detection of deception for voice analysis.

Lynch, B. E., & Henry, D. R. (1979). A validity study of the psychological stress evaluator. Canadian Journal of Behavioural Science, 11(1), 89-94.
Conclusion: Chance level detection of stress using the voice.

O'Hair, D., Cody, M. J., & Behnke, R. R. (1985). Communication apprehension and vocal stress as indices of deception. The Western Journal of Speech Communication, 49, 286-300.
Conclusions: Only one subgroup showed a detection rate significantly better than chance, and it did so by the thinnest of margins. Use of questionable statistical methods in this study suggests the modest positive findings would not be replicated in other research. See next citation.

O'Hair, D., Cody, M. J., Wang, S., & Chao, E. Y. (1990). Vocal stress and deception detection among Chinese. Communication Quarterly, 38(2, Spring), 158ff.
Conclusion: Partial replication of above study. Vocal scores were not related to deception.

Suzuki, A., Watanabe, S., Takeno, Y., Kosugi, T., & Kasuya, T. (1973). Possibility of detecting deception by voice analysis. Reports of the National Research Institute of Police Science, 26(1, February), 62-66.
Conclusion: Voice measures were not reliable or useful.

Timm, H. W. (1983). The efficacy of the psychological stress evaluator in detecting deception. Journal of Police Science and Administration, 11(1), 62-68.
Conclusion: Chance-level detection of deception.

Waln, R. F., & Downey, R. G. (1987). Voice stress analysis: Use of telephone recordings. Journal of Business and Psychology , 1(4), 379-389.
Conclusions: Voice stress methodology did not show sufficient reliability to warrant its use as a selection procedure for employment.

Other reports, research on validity of voice-stress analysis lie detection:

The Virginia Department of Occupational Professionalism and Regulation prepared a report on voice stress. This document was pivotal in the decision by the Virginia State Legislature to disallow the use of computer voice stress analyzers in criminal investigations.
"A review of the literature revealed that there have been no scientific studies conducted, to date, to measure the validity of the computer stress analyzed to detect deception," concluded a November 2003 study by the Virginia Department of Professional and Occupational Regulation. "It has been argued that the computer stress analyzer is more cost effective, convenient, and more user friendly than the traditional polygraph equipment, however, one question still remains unanswered: how reliable is the equipment in its actual ability to detect, measure, and display changes in voice frequency? Has it ever been scientifically measured? The answer to this question is 'no.'"

Similar conclusions were reached in "Voice Stress Devices and the Detection of Lies", an overview of current voice-stress technologies written by Donald J. Krapohl, Andrew H. Ryan and Kendall W. Shull; and published in Policy Review, the official publication of the International Chiefs of Police National Law Enforcement Policy Center.

According to a recent study funded by the National Institute of Justice (NIJ), two of the most popular VSA programs in use by police departments across the country - Computer Voice Stress Analyzer® (CVSA®) and Layered Voice Analysis (LVA) - are no better than flipping a coin when it comes to detecting deception regarding recent drug use. The study's findings also noted, however, that the mere presence of a VSA program during an interrogation may deter a respondent from giving a false answer.

A website has been developed which details the current research and legislation regarding Voice Stress Analysis. A current set of internet links has been complied at http://voicestress.org that links to the relevant research on voice stress validity.

YouTube has the ABC PrimeTime News Video on the "Expose of Charles Humble" piece on CVSA online (view it online)

Voice-stress analysis is fairly effective in identifying certain variations in stress levels in human speech, but high levels of stress do not necessarily correlate with deception. It may someday be possible to refine voice-stress analysis so that it is capable of distinguishing among various sources of stress and accurately identifying those that are directly related to deception. However, all the research suggests that it's wishful thinking, at best, to suggest that current voice-stress analysis systems are capable or reliably detecting deception.