Lie detection is the practice of determining whether someone is
lyingA lie is a type of deception in the form of an untruthful statement, especially with the intention to deceive others, often with the further intention to maintain a secret or reputation, protect someone's feelings or to avoid a punishment...
. Activities of the body not easily controlled by the conscious mind are compared under different circumstances. Usually this involves asking the subject control questions where the answers are known to the examiner and comparing them to questions where the answers are not known. Critics claim that "Lie detection" by use of polygraphy has no scientific validity because it is not a scientific procedure.
Lie detection commonly involves the
polygraphA polygraph is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration, breathing rhythms, body temperature and skin conductivity while the subject is asked and answers a series of questions, on the theory that false answers will produce...
.
Lie detection is the practice of determining whether someone is
lyingA lie is a type of deception in the form of an untruthful statement, especially with the intention to deceive others, often with the further intention to maintain a secret or reputation, protect someone's feelings or to avoid a punishment...
. Activities of the body not easily controlled by the conscious mind are compared under different circumstances. Usually this involves asking the subject control questions where the answers are known to the examiner and comparing them to questions where the answers are not known. Critics claim that "Lie detection" by use of polygraphy has no scientific validity because it is not a scientific procedure.
Polygraph
Lie detection commonly involves the
polygraphA polygraph is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration, breathing rhythms, body temperature and skin conductivity while the subject is asked and answers a series of questions, on the theory that false answers will produce...
.
Voice stress analysisVoice Stress Analysis is a controversial lie detection technology. It has been described as pseudoscientific, and there is no known scientific basis for the underlying theory of "microtremors". Federally funded research showed "little validity" in the technique....
may also be commonly used because it can be applied covertly to monitor voice recordings. The
polygraphA polygraph is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration, breathing rhythms, body temperature and skin conductivity while the subject is asked and answers a series of questions, on the theory that false answers will produce...
detects changes in body functions not easily controlled by the conscious mind. This includes bodily reactions like skin conductivity and
heart rateHeart rate is determined by the number of heartbeats per unit of time, typically expressed as beats per minute , it can vary with as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and...
.
Cognitive Polygraphy
Recent developments that permit non-invasive monitoring using functional transcranial Doppler (fTCD) technique led
Njemanze to postulate that successful problem-solving employs a discrete knowledge strategy (DKS) that selects neural pathways represented in one hemisphere, while unsuccessful outcome implicates a non-discrete knowledge strategy (nDKS). A polygraphic test could be viewed as a working memory task. This suggests that the DKS model may have a correlate in mnemonic operations. In other words, DKS model may have a discrete knowledge base (DKB) of essential components needed for task resolution, while for nDKS, DKB is absent and, hence, a "global" or bi-hemispheric search occurs. Based on the latter premise, a 'lie detector' system was designed as described in . A pattern of blood-flow-velocity changes is obtained in response to questions that include correct and incorrect answers. The wrong answer will elicit bi-hemispheric activation, from correct answer that activates unilateral response. Cognitive polygraphy based on this system is devoid of any subjective control of mental processes and, hence, high reliability and specificity; however, this is yet to be tested in forensic practice. See also cognitive
biometricsBiometrics refers to methods for uniquely recognizing humans based upon one or more intrinsic physical or behavioral traits. In information technology, in particular, biometrics is used as a form of identity access management and access control...
.
fMRI
An fMRI can be used to compare brain activity differences for truth and lie. Research does not currently support the use of fMRI to detect deception in "real world individual cases" (Kozel et al., 2004).
In episode 109 of the popular science show
MythbustersMythBusters is a popular science television program produced by Australian company Beyond Television Productions originally for the Discovery Channel in the United States. The series has since been distributed by a number of international broadcasters, including SBS in Australia and BBC2 in the UK...
, the three members of the build team attempted to fool an fMRI test. Although two of them were unsuccessful, the third was able to successfully fool the machine, suggesting that fMRI technology still requires further development.
Brain observations
ElectroencephalographyElectroencephalography is the recording of electrical activity along the scalp produced by the firing of neurons within the brain . In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from...
is used to detect changes in brain waves.
Brain fingerprintingBrain Fingerprinting is a controversial forensic science technique that determines whether specific information is stored in a subject’s brain by measuring electrical brainwave responses to words, phrases, or pictures that are presented on a computer screen . Brain fingerprinting was invented by...
uses
electroencephalographyElectroencephalography is the recording of electrical activity along the scalp produced by the firing of neurons within the brain . In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from...
to determine if an image is familiar to the subject. This could detect deception indirectly but is not a technique for lie detecting.
Cognitive chronometryCognitive chronometry refers to the systematic measurement of response time as a means of illuminating either mental operations or mental associations. Two measuring instruments relying on cognitive chronometry are the Implicit Association Test, or IAT, and the Timed Antagonistic Response...
, or the measurement of the time taken to perform mental operations, can be used to distinguish lying from truth-telling. One recent instrument using cognitive chronometry for this purpose is the
Timed Antagonistic Response AlethiometerThe Timed Antagonistic Response Alethiometer, or TARA, is a type of lie detection technique that relies upon cognitive chronometry.The TARA is a computer-based technique. It requires respondents to classify a succession of mixed statements as true or false, as quickly and accurately as they can, by...
, or TARA.
Drugs
Truth drugA truth drug is a psychoactive medication used to obtain information from subjects who are unable or unwilling to provide it otherwise. The unethical use of truth drugs is classified as a form of torture according to international law However, they are properly and productively utilized in the...
s such as
sodium thiopentalSodium thiopental, better known as Sodium Pentothal , thiopental, thiopentone sodium, or trapanal, is a rapid-onset short-acting barbiturate general anaesthetic. It is an intravenous ultra-short-acting barbiturate...
are used for the purposes of obtaining accurate information from an unwilling subject. Information obtained by publicly-disclosed truth drugs has been shown to be highly unreliable, with subjects apparently freely mixing fact and fantasy. Much of the claimed effect relies on the belief of the subject that they cannot tell a lie while under the influence of the drug.
Controversy
In the peer reviewed academic article "Charlatanry in forensic speech science", the authors reviewed 50 years of lie detector research and came to the conclusion that there is no scientific evidence supporting that lie detectors actually work. Lie detector manufacturer
NemesyscoNemesysco is an Israeli company that makes lie detectors and other products based on voice analysis. They have been used in airports in Israel and Russia, by insurance companies and social security helplines in the United Kingdom and sold to consumers. It has raised controversy about privacy and...
sued the academic publisher for libel and forced a removal of the article from the online databases. In a letter to the publisher Nemesysco's lawyers wrote that the authors of the article could be sued for defamation if they wrote on the subject again.
The cumulative research evidence suggests that machines do detect deception better than chance, but with significant error rates and that strategies used to "beat" polygraph examinations, so-called countermeasures, may be effective. Despite unreliability, results are
admissibleAdmissible evidence, in a court of law, is any testimonial, documentary, or tangible evidence that may be introduced to a factfinder--usually a judge or jury--in order to establish or to bolster a point put forth by a party to the proceeding...
in court in some countries such as the United States and Canada.