Lie detection is an assessment of a verbal statement with the goal to reveal a possible intentional deceit. Lie detection may refer to a cognitive process of detecting deception by evaluating message content as well as non-verbal cues. Typically, people are not as good at detecting lies as they think they are. The average person can only detect lying with chance accuracy, and experts, including law enforcement, are not significantly better at it. There are a number of reasons as to this — the average person also does not expect others to lie to them and instinctively believes others are being truthful.
Lie detection may also refer to questioning techniques used along with technology that record physiological functions to ascertain truth and falsehood in response. The latter is commonly used by law enforcement in the United States, but rarely in other countries because it is based on pseudoscience. There are a wide variety of technologies available for this purpose. The most common and long used measure is the polygraph. A comprehensive 2003 review by the National Academy of Sciences of existing research concluded that there was "little basis for the expectation that a polygraph test could have extremely high accuracy." There is no evidence to substantiate that non-verbal lie detection, such as by looking at body language, is an effective way to detect lies, even if it is widely used by law enforcement.
Cues of Deception There are several verbal cues that could indicate someone is being deceptive. Liars tend to give briefer and more vague statements that are detached from the self. Highly structured stories that have fewer details lower the potential risk of inconsistency, but they also often lack contextual and sensory detail as a result. Liars have also been shown to avoid amending their statements in favour of definitive stories, while people who are telling the truth will correct themselves more naturally and provide less perfect memory traces. Since lying requires more cognitive load than being truthful, people who are being deceptive may also be slower to respond and speak in shorter statements that have more pauses and simpler grammar. However, these cues are highly variable between individuals due to factors including experience with lying, motivation, cultural norms, and cognitive ability, and therefore have low predictive power.
There are several non-verbal cues that are popularly believed to imply that someone is lying, including avoiding eye contact and fidgeting and touching their face more. However, it has been found that these cues are not consistent indicators of lying, and reflect common theories rather than reliable support. Some studies have found non-verbal differences between liars and truth tellers, but they are statistically small and conflicting. For example, increased cognitive load due to lying may be reflected in non-verbal cues such as decreased and slower movement, but this difference is so subtle it is overshadowed by variability between individuals. As with verbal cues of deception, non-verbal behaviour is strongly influenced by factors including culture, personality, and mental health, making the reliability of non-verbal cues inconsistent.
General accuracy and limitations of assessment
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.The Truth About Lie Detectors. American Psychological Association. Despite unreliability, results are admissible in court in some countries, such as Japan. Lie detector results are very rarely admitted in evidence in the US courts.
In 1983 the U.S. Congress Office of Technology Assessment published a review of the technology and found: "...there is at present only limited scientific evidence for establishing the validity of polygraph testing. Even where the evidence seems to indicate that polygraph testing detects deceptive subjects better than chance, significant error rates are possible, and examiner and examinee differences and the use of countermeasures may further affect validity."
In the 2007 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 voice analysis lie detectors actually work. Lie detector manufacturer Nemesysco threatened to sue the academic publisher for libel resulting in removal of the article from 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.All lies? Scientists threatened with legal action over lie detector article . Stockholm University.Threats over Swedish lie detector research . The Local. January 27, 2009.Online at:
Nevertheless, extraneous "noise" on the polygraph can come from embarrassment or anxiety and not be specific to lying. When subjects are aware of the assessment their resulting emotional response, especially anxiety, can impact the data. Additionally, psychological disorders can cause problems with data as certain disorders can lead a person to make a statement they believe to be truth but is actually a fabrication. As well as with all testing, the examiner can cause biases within the test with their interaction with the subject and interpretation of the data.
History
20th century The study of physiological methods for deception tests measuring emotional disturbances began in the early 1900s. Vittorio Benussi was the first to work on practical deception tests based on physiological changes. He detected changes in inspiration-expiration ratio—findings confirmed by N.E. Burtt. Burtt conducted studies that emphasized the changes in quantitative systolic blood-pressure. William Moulton Marston studied blood-pressure and noted increase in systolic blood pressure of 10 mm Hg or over indicated guilt through using the tycos sphygmomanometer, with which he reported 90–100% accuracy. His studies used students and actual court cases. Then in 1913 W.M. Marston determined systolic blood-pressure by oscillatory methods and his findings cite definite changes in blood pressure during the deception of criminal suspects. In 1921, John Augustus Larson criticized Marston's intermittent blood pressure method because emotional changes were so brief they could be lost. To adjust for this he modified the Erlanger sphygmograph to give a continuous blood pressure and pulse curve and used it to study 4,000 criminals. In the 1990s, a team of scientists, Stanley Abrams, Jean M. Verdier and Oleg Maltsev developed a new methodology contributing six coefficients that positively affect the accuracy of the lie detector analysis results.
21st century Two meta-analyses conducted by 2004 found an association between lying and increased pupil size and compressed lips. Liars may stay still more, use fewer hand gestures, and make less eye contact. Liars may take more time to answer questions but on the other hand, if they have had time to prepare, they may answer more quickly than people telling the truth would, and talk less, and repeat phrases more. They do not appear to be more fidgety, blink more, or have a less-relaxed posture.
Paul Ekman has used the Facial Action Coding System (FACS) and "when combined with voice and speech measures, [it] reaches detection accuracy rates of up to 90 percent." However, there is currently no evidence to support such a claim. It is currently being automated for use in law enforcement and is still being improved to increase accuracy. His studies use micro-expressions, which last less than one-fifth of a second, and "may leak emotions someone wants to conceal, such as anger or guilt." However, "signs of emotion aren't necessarily signs of guilt. An innocent person may be apprehensive and appear guilty," Ekman reminds us. With regard to his studies, lies about emotions at the moment have the biggest payoff from face and voice cues while lies about beliefs and actions, such as crimes use cues from gestures and words are added. Ekman and his associates have validated many signs of deception, but do not publish all of them so as not to educate criminals
James Pennebaker uses the method of Linguistic Inquiry and Word Count (LIWC), published by Lawrence Erlbaum, to conduct an analysis of written content. He claims it has accuracy in predicting lying. Pennebaker cites his method as "significantly more effective than human judges in correctly identifying deceptive or truthful writing samples"; there is a 67% accuracy rate with his method, while trained people have 52% accuracy. There were five experimental procedures used in this study. Study 1–3 asked participants to speak, hand write or type a true or false statement about abortion. The participants were randomly assigned to tell a true or false statement. Study 4 focused on feelings about friends and study 5 had the students involved in a mock crime and asked to lie. Human judges were asked to rate the truthfulness of the 400 communications dealing with abortion. The judges read or watched the statement and gave it a yes or no answer about if this statement was false or not. LIWC correctly classified 67% of the abortion communications and the judges correctly classified 52%. His studies have identified that deception carries three primary written markers. The first is fewer first-person pronouns such as 'I', 'me', 'my', 'mine', and 'myself' (singular), as well as 'we', 'us', 'our', and 'ourselves' (plural). Those lying "avoid statements of ownership, distance themselves from their stories and avoid taking responsibility for their behavior" while also using more negative emotion words such as "hate, worthless and sad." Second, they use "few exclusionary words such as except, but or nor" when "distinguish[ing] what they did from what they did not do."
More recently evidence has been provided by the work of CA Morgan III and GA Hazlett that a computer analysis of cognitive interview derived speech content (i.e. response length and unique word count) provides a method for detecting deception that is both demonstrably better than professional judgments of professionals and useful at distinguishing between genuine and false adult claims of exposure to highly stressful, potentially traumatic events. This method shows particular promise as it is non confrontational as well as scientifically and cross culturally valid.
Questioning and testing techniques
There are typically three types of questions used in polygraph testing or voice stress analysis testing:
Irrelevant questions establish a baseline to compare other answers by asking simple questions with clear true and false answers.
Comparison questions have an indirect relationship to the event or circumstance, and they are designed to encourage the subject to lie.
Relevant questions are compared against comparison questions (which should represent false answers) and irrelevant questions (which should represent true answers). They are about whatever is particularly in question.
The control question test (CQT) uses control questions, with known answers, to serve as a physiological baseline in order to compare them with questions relevant to a particular incident. The control question should have a greater physiological response if truth was told and a lesser physiological response for lying. The guilty knowledge test (GKT) is a multiple-choice format in which answer choices or one correct answer and additional incorrect answers are read and the physiological response is recorded. The controls are the incorrect alternative answers. The greater physiological response should be to the correct answer. Its point is to determine if the subject has knowledge about a particular event.