Voice stress analysis
Voice Stress Analysis (VSA) technology is said to record psychophysiological stress responses that are present in human voice, when a person suffers psychological stress in response to a stimulus (question) and where the consequences may be dire for the subject being 'tested'.
The technique's accuracy remains debated. There are no independent research studies that support the use of VSA as a reliable lie detection technology, whilst there are numerous studies that dispute its reliability.
Voice Stress Analysis (VSA) remains a controversial lie detection technology. It has been described as pseudoscientific. While there is a wealth of scientific basis for the underlying theory of "microtremors," this data is based predominantly upon research on skeletal muscle (i.e. calf, finger).
Federally funded research via the American Polygraph Association in the United States showed "little validity" in the technique.
There is tension between the voice stress analysis community and the polygraph community, due in the main to the fact that the polygraph is heavily regulated and has been subject to numerous detailed, contentious scientific studies, while voice stress analysis is largely unregulated. However, there are few studies which show VSA results to be even slightly better than chance.
In Anders Eriksson and Francisco Lacerda's article "Charlatanry in forensic speech science: A problem to be taken seriously" voice stress analysis is described as charlatanry, and that analysis of studies shows that these methods perform at chance levels. They argue that "there are serious ethical and security reasons to demand that responsible authorities and institutions should not get involved in such practices." This article was criticized by manufacturers of voice stress analysis machines. Due to the controversy, the International Association of Forensic Linguists' peer-reviewed journal International Journal of Speech, Language and the Law withdraw the article. However, there have no subsequent studies that refute the findings contained within that article.
Principle and origins
VSA is distinct from Layered Voice Analysis (LVA). The main difference in the method of operation between LVA and VSA is based on the analyzed frequencies ranges: while VSA focuses on the 8–14 Hz range which is recorded via an omni-directionalphone. LVA utilises components of the voice such as pitch and tone, which are conrollable by the user, also varying according to his/her emotions at time of utterance. Change of emotions produce unreliable results being not particularly relevant to DOD.
The original VSA technology was devised by three former US Army personnel from the Counterintelligence Electronic Div. The three, Bell, McQuiston & Ford, developed the PSE 1, an analogue machine. The same three, working under Dektor Counterintelligence and Security Inc., manufactured the Phoenix telephone analyzer, the PSE 1000 and later the PSE 2000.
VSA technology together with validated testing protocols, is designed to protect the innocent and avoid 'false positive' results. VSA is designed to assist any investigation by establishing the veracity of a subject's verbal responses.
There are no known physical countermeasures for VSA. Conversely according to Honts et al., the simple use of a 'tack' placed under the tongue of the examinee, to be used as a countermeasure, can reduce the accuracy of polygraph results from 98% to 26%.
Methodology and accuracy
The recorded "micro tremors" in a person's voice are converted via the algorithm into a scorable voice gram. The discrepancy in researched accuracy may result from incorrectly trained or non-trained persons utilizing the technology incorrectly. This is evident by some Polygraphists trying to "test" VSA technology without having received accredited training in the use thereof.
In 2002, Clifton Coetzee, a polygraph and VSA instructor, devised a scoring method for voice grams incorporating the 'UTAH 7 Point' scoring system, as used by modern day polygraphists. Reactive or Responsive patterns are assigned a weighting of +3 to -3.
In 2010 through to 2011, Clifton Coetzee and Jean-Louis Gouin (Alpes-Software: Contracted Developer of original Diogenes Lantern, which is now re-labelled as TDT )developed AVSA PRO with the assistance of Truth & Development Technologies, which is a unique, evolutionary, fully automatic VSA system. AVSA PRO is programmed to cater for cadence control being consistent in every question posed. Examiner induced errors have been eliminated. AVSA PRO is based on a neural network - another major innovation in the worldwide vsa industry. Scoring of automatically captured and numerically identified voice wavs is according to the neural network database, developed from Expert blind scoring of 000's of voice wavs, with the input of known outcomes.
The American Polygraph Association's website lists conclusions from multiple studies, into the accuracy of voice stress analysis as a means of detecting the subject's truthfulness. Some researchers or polygraph professionals cast doubt on the validity of the results of such tests; many describe the results as no better than chance.
The National Academy of Sciences published a 2003 study on the polygraph, in which they concluded that the evidence of its efficacy is "scientifically weak." According to the American Psychological Association, "most psychologists agree that there is little evidence that polygraph tests can accurately detect lies".
Notable examples of use
Following the 2012 case in which George Zimmerman fatally shot Florida teenager Trayvon Martin, Zimmerman was given a voice stress analysis test by the police department of Sanford, Florida. He passed the test. A videotape of the test was publicly released in June 2012.
- Ruiz, Selye, & 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”
- Everding, Gerry (February 10, 2004). "Research casts doubt on voice-stress lie detection technology". Washington University in St. Louis.
- Horvath, F. "Detecting deception: the promise and the reality of voice stress analysis." Journal of Forensic Science. 1982 Apr;27(2):340-51. PMID 7047675
- As documented by Olof Lippold – The Lippold Tremor.
- Refer NAS 2003 in reference to all APA related research projects.
- Haddad, Walters Study 2002, doc 193832
- Eriksson, Anders; Lacerda, Francisco (2007). "Charlatanry in forensic speech science: A problem to be taken seriously". (PDF File) The International Journal of Speech, Language and the Law. Equinox Publishing. IJSLL (print) issn 1748-8885 IJSLL (online) issn 1748-8893
- "Lie Detector Company Threatens Critical Scientists With Suit". Slashdot. 2009-01-29. Retrieved 2009-02-02.
- The Diogenes Company. Retrieved 9 February 2009.
- 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".
- Honts 1993
- Honts, C. R., and Hodes, R. L., “The Effect of Simple Physical Countermeasures on the Detection of Deception," paper presented at meetings of the Society for Psychophysiological Research, Minneapolis, Minn., 1982.
- Honts, C. R., and Hodes, R. L., “The Effects of Multiple Physical Countermeasures on the Detection of Deception," Psychophysiology 19:564-565 (abstract), 1982.
- Honts, C. R., and Hodes, R. L., “The Effect of Simple Physical Countermeasures on the Detection of Deception," Psychophysiology 19:564 (abstract), 1982.
- Honts, C. R., Raskin, D. C., and Kircher, J. C., "Detection of Deception: Effectiveness of Physical Countermeasures Under High Motivation Conditions," 1 paper presented at meetings of the Society for Psychophysiological Research, September 1983.
- Cal Pen Code § 637.3
- Cal Pen Code § 637.2
- "Over 1700 Agencies Utilizing the CVSA".[dead link]
- see W.Carolina Uni paper 140 , Eng 101 , 2008 Tay, Adams, etc.
- Air Force Research Laboratory, Rome, New York, October, 2000
- Chapman, J. Criminal Justice Department, Corning Community College, New York. "The Psychological Stress Evaluator As A Tool For Eliciting Confessions", 1989. Chapman selected 211 criminal responses at random from 2,109 known-conclusion responses 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 responses where deception was indicated.
- Truth Extraction ISBN 0-86486-464-7
- 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 (Available from Library of Congress)
- 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 (Available from Library of Congress).
- Cestaro, V. Department of Defense Polygraph Institute, Ft. McClellan, AL. "A Comparison Between Decision Accuracy Rates Obtained Using the Polygraph Instrument and the Computer Voice Stress Analyzer in the Absence of Jeopardy", August, 1995.
- "Conclusions and Recommendations" The Polygraph and Lie Detection (2003) National Academies Press. p. 212
- "The Truth About Lie Detectors (aka Polygraph Tests)". American Psychological Association. August 5, 2004. Retrieved August 14, 2013.
- Kovaleski, Serge F. (May 16, 2012). "Trayvon Martin Case Shadowed by Series of Police Missteps". The New York Times. Retrieved May 22, 2012.
- Stutzman, Rene (June 21, 2012). "Tape released of Zimmerman’s re-enactment of Martin shooting". Orlando Sentinel.