Terms Relating to Lie Detectors Explained – Letter L
Labile Unstable, inconsistent, or dynamic. PDD tracings that display a highdegree of responsibility or broad amplitude changes are referred to as labile.Laboratory ResearchScientific investigation in which experimental procedures are designed tomimic real-world circumstances, but in which there is direct control over theindependent variables.Lafayette Instrument CompanyAn American manufacturer of polygraphs, both analog andcomputerized, founded by Max Wastl. Headquarters is located in Lafayette,Indiana.LanternA voice stress device. The Diogenes Company produces the Lantern,first introduced in 1998. Examiner certification is required. The Lanterntesting format is dissimilar to PDD formats. See voice stress analysis.Larson, JohnOne of the first modern researchers in PDD, Dr. Larson first usedcontinuous recordings of respiratory and vasomotor activity with a test formatusing relevant and irrelevant questions. Dr. Larson’s 1932 book, Lying and ItsDetection, provided the best scientific evaluation of PDD up to that time.LatencyThe delay between stimulus presentation and some aspect of theresponse. Onset latency relates to the delay between the stimulus presentationand the beginning of the response, while the peak latency uses the time of themaximum amplitude of the response as the second point. Latencies of specificphysiologic responses vary. The latency of an electrodermal response, forexample, from stimulus onset is about one to three seconds for the averageperson, while hormonal influences on blood pressure require several secondsmore. A significant departure from typical latencies can indicate that a givenresponse is unrelated to the stimulus, that there are problems in attention forthe subject, or that countermeasures are being engaged. Because of individualdifferences, within-subject analyses are warranted.Law of Initial Values (LIV)The magnitude of a given physiologic response will be constrained by thelevel of arousal present when the response begins. If a response occurs whenarousal is already high, the amplitude of the response measured from onset tomaximum expression will be less than if the same response occurred during amedian level. While there are differing opinions regarding thispsychophysiologic principle, it can certainly be said that all biological systemsdo have upper limits in their potential for response, and ceiling effects cancome into play. This is because compensatory systems mediated via thesympathetic and parasympathetic nervous systems work to limit responseintensities. Additionally, concrete limitations may exist, such as the finitenumber of sweat glands establishes the maximum electrodermal response.Layered Voice Analysis (LVA)A voice-based technology sold as a means of detecting emotions anddeceit. LVA was developed in Israel by Amir Liberman, owner of Nemesysco,Ltd, and is sold in the US through Voice Analysis Technologies in Madison,Wisconsin. The LVA software operates on a laptop computer, and appliesnumerous algorithms to the voice signal to assess a wide range of factors. Thecompany has a very assertive promotional campaign. The company alsoattempts to distance this technology from the Computer Voice Stress Analyzer(CVSA) in part because of reports of poor validity for the CVSA, and thedifferent approach to analysis of voice data. Research on the LVA has found itsvalidity to be poor to none. See: Damphousse, Pointon, Upchurch & Moore(2007); Harnsberger, Hollien, Martin & Hollien (2009); Hollien & Harnsberger(2006).Law of IntensityWithin limits, response magnitudes and stimulus intensities share a loglinearrelationship; the stronger the stimulus, the greater the magnitude of theresponse. Response magnitudes are used in PDD to infer the type of questionthe examinee considers most salient or threatening.Lens ModelModel for studying the decision rules used by human decision-makers,first proposed by E. Brunswik in the early 1950s. Conceptually, the modelcharacterizes the decision process as the selection and evaluation of cues inthe assessing of reality. Which cues are used and how they are weighted arecentral to this model. The term lens model springs from the sense that subjectsview reality through the lens of these cues. This approach has been applied inthe study of PDD decisions at the University of Utah. The lens model is usefulto assess the diagnosticity of physiological responses, in identifying howexaminers use the physiological information, and to determine the combinationand weights of the cues that will maximize decision accuracy. See: Kircher &Raskin (1983); Kircher, J.C., Raskin, D.C., Honts, C.R., & Horowitz, S.W.(1995).Law Enforcement Pre-Employment Test (LEPET)A form of the Air Force Modified General Question Test (AFMGQT) whichuses specific relevant questions, and is used for police candidate screening.lie detectorA common but inaccurate term for the polygraph.Lie QuestionRarely used terminology for probable lie comparison question.Likelihood RatioThe Likelihood Ratio (LR) provides an index of how much a test result willchange the probability or odds of having a condition after a known or assumed prior incidence rate (base rate). In the case of polygraph testing, the conditionof interest is involvement in the issue under investigation. The LR+ tells us howmuch more likely it is that a person is lying than not, after failing a polygraphtest, compared with the likelihood before he or she sat in the chair andcompleted the test. If a person produces a truthful test result, the LR- tells ushow much more likely are a person is to be telling the truth than before thetest. LRs may also be used to compare the efficacy of two or more scoring anddecision models, for a given or assumed base rate. The advantage of the LR,compared with traditional Bayesian metrics such as positive predictive value(PPV) and negative predictive value (NPV) is that the LR is inclusive ofinconclusive results, and will provide information that more accuratelygeneralizes to field settings.Limestone TechnologiesA Canadian manufacturer of computerized polygraph instruments.Headquartered in Odessa, Ontario, Canada.Lombroso, CesareItalian physician biologist who first employed instrumentation in aneffort to detect deception in suspects in live criminal investigations. Hereported in 1885 in the second edition of his book, L’Homme Criminel the use ofthe “hydrosphygmograph,” a mechanical arrangement invented for medicalpurposes, to detect blood pressure changes during interrogation. One of hisstudents, Angelo Mosso, also went on to perform instrumental deceptiondetection experiments.Loyalty ExaminationSee Counterintelligence-Scope Polygraph.Luria, AleksandrRussian researcher and originator of the conflict theory, one of thetheories proffered to explain the psychophysiological mechanisms underlyingPDD. Luria did deception detection experiments with a tremograph. See: Luria(1930); Runkel (1936).Lykken, David T.Psychologist and ardent critic of the CQT who passed away in 2006. Dr.Lykken produced numerous writings for the scientific and general press,including a book, A Tremor in the Blood, in which he argued strongly that theCQT is fatally flawed, that it resulted in wrongful criminal convictions, and itwas vulnerable to countermeasures by the guilty. Dr. Lykken did not publishany research of his own on the CQT, but used anecdotal histories andinterpretations of other research to form his arguments. Lykken endorsed theGuilty Knowledge Test (GKT, now known as the Concealed Information Test),an alternate PDD testing format. The GKT has not been widely used outside ofJapan. See: Lykken (1998).Lykken scoringSystem of scoring electrodermal responses in the Concealed InformationTest (formerly the Guilty Knowledge Test) and establishing the threshold fordecisions. The Lykken scoring system compares the responses of the criticaltest items in a rank order method against those of the neutral items. Onevariant uses averaged ranks. See: Lykken (1998).
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