Australian Polygraph Services - Polygraph Testing and Lie Detection for When The Truth Matters

Is Voice Stress Analysis accurate?

No. Independent research shows that Voice Stress Analysis is not as accurate as the promoters of Voice Stress Analysis would have you believe. In recent times Computer Voice Stress Analysis (CVSA) has been promoted and used as a much cheaper alternative to polygraph testing without inconclusive results. The manufacturers and supporters of CVSA claim that Voice Stress Analysis can differentiate between truth and deception. Independent research however (see below) shows that Voice Stress Analysis is not an accurate discriminator between truth and deception. In fact most studies relating to CVSA have shown that its accuracy is often no better than chance.

In studies conducted by the US. Department of Defence research concluded that "... very few studies have found that voice stress analysis worked better than chance at detecting deception" and "The preponderance of evidence indicates the polygraph is far more accurate at detecting deception than is voice stress analysis".

For further information read the following:

• Voice Stress Analysis wrongful prosecution allegations
• Police use of Voice Stress Analysis generates controversy
• The accuracy of polygraph testing versus Voice Stress Analysis
• Voice Stress devices and the detection of lies

Scientific Studies on the poor accuracy of Computer Voice Stress Analysis

Various independent scientific studies have been conducted on the accuracy of Computer Voice Stress Analysis. 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 CVSA device in particular, while others investigated whether voice stress analysis in general could be used to detect stress or deception. The conclusions relating to CVSA's poor accuracy in each study are reported below:

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.

US. Department of Defence Position Statement on Voice Stress Analysis

September 11, 1996

The Department of Defence has investigated the scientific value of voice stress analysis. We reviewed the research literature on voice stress analysis. Only one voice stress device, the CVSA, is being widely marketed. We purchased the CVSA, and sent two researchers to the CVSA school for training by the manufacturer. We conducted several studies on voice stress analysis, using standard laboratory voice equipment and software and also using the CVSA device. We solicited the manufacturer's advice in designing the CVSA studies, and used both our own scientists and CVSA practitioners recommended by the CVSA manufacturer to gather the research data.

Conclusions;

1. To date, we have found no credible evidence in information furnished by the manufacturers, the scientific literature, or in our own research, that voice stress analysis is an effective investigative tool for determining deception.
2. Few studies have found that voice stress analysis worked better than chance at detecting deception. Unfortunately, these results are not consistent, nor are the reported accuracies nearly as good as those normally reported for the polygraph. Hundreds of studies have shown that when properly trained examiners use the polygraph under controlled conditions, their decisions can be highly accurate in discriminating between truthful and deceptive people.
3. The preponderance of evidence indicates the polygraph is far more accurate at detecting deception than is voice stress analysis. No Department of Defence agency uses any form of voice stress analysis for investigative purposes.