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Charlatanry and Fraud – an increasing problem for forensic phonetics? Anders Eriksson Department of Linguistics, Gothenburg University, Gothenburg, Sweden.

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Presentation on theme: "Charlatanry and Fraud – an increasing problem for forensic phonetics? Anders Eriksson Department of Linguistics, Gothenburg University, Gothenburg, Sweden."— Presentation transcript:

1 Charlatanry and Fraud – an increasing problem for forensic phonetics? Anders Eriksson Department of Linguistics, Gothenburg University, Gothenburg, Sweden

2 Charlatanry and Fraud Is the problem really increasing, and if so, in what sense? In quantitative terms? In terms of the damage it does?

3 Charlatanry and Fraud In my talk I will present two cases of bogus lie detectors. Why, one might ask, have I chosen lie detectors to exemplify fraud in the field of forensic phonetics?

4 Charlatanry and Fraud Two of the most widely marketed bogus products today are claimed to be lie detectors They are both said to be based on principles that are correlated with properties of the human voice.

5 Charlatanry and Fraud Let me begin by saying a few words about the basic ideas behind so called lie detectors.

6 Charlatanry and Fraud Lie detectors are meant to be used to find the truth or falsity of statements when it cannot be determined by logical deduction or circumstantial evidence

7 Charlatanry and Fraud The assumption underlying lie detectors is that there are observable behavioral differences between telling a lie and telling the truth.

8 Charlatanry and Fraud It is generally assumed that one such observable difference is an increase in the stress level when telling a lie.

9 The most well known “lie detector” is the so called Polygraph. Its first appearance can be dated back to A more refined version was used in a court case in 1923 and Polygraphs have been used ever since with some refinements. Charlatanry and Fraud

10 The basic idea behind the Polygraph is that if you can register the involuntary reactions we know to be correlated with stress (respiration, pulse, blood pressure, and galvanic skin respons (e.g.“palm sweat”), these signs can be used to detect lies and deception. Charlatanry and Fraud

11 A typical Polygraph setup. Charlatanry and Fraud

12 The problem with the Polygraph as a lie detector is in the interpretation. Correlations between stress levels and pulse for example are found as group results. To generalize from group results to individuals is, of course, not a valid step. Nor is it a valid step to conclude that a person who experiences stress must necessarily be lying. Charlatanry and Fraud

13 The basic idea behind “lie detectors” based on voice analysis is that there are properties in the voice signal that may be reliably correlated with stress, and as a consequence with lie and deception. Charlatanry and Fraud

14 Voice stress analysis (VSA), also called Perceptual Stress Evaluation (PSE), based on the monitoring of so called micro tremor is such a method. Charlatanry and Fraud

15 But whereas there are scientifically established correlations between stress and the indicators used by the Polygraph, there is no scientific basis for the voice stress analysis at all. Charlatanry and Fraud

16 In the sixties it was discovered that in larger muscles like the biceps there is involuntary tremor, called micro tremor, with a frequency in the 8 to 12 Hz range. Charlatanry and Fraud

17 This gave rise to speculations that the same phenomenon might be present in the larynx muscles and that it may affect the voice source frequency. In particular it was suggested that the tremor might vary as a function of stress in the speaker. Charlatanry and Fraud

18 Before anybody had a chance to investigate the possible occurrence of micro tremor in the voice, the first ”lie detector” based micro tremor in the voice source appeared. Charlatanry and Fraud

19 Already in 1981 Shipp and Izdebski published results from an experimental study where they used hooked-wire electrodes inserted into the larynx muscles in order to investigate the possible occurrence of micro tremor, but no micro tremor patterns at all were found. Charlatanry and Fraud

20 And later studies have confirmed these results. So what the VSA analyzers do is measure the variation in something that isn’t even there, in itself an achievement of sorts. Charlatanry and Fraud

21 But they do make pretty diagrams! Charlatanry and Fraud

22 If the people who use these gadgets don’t know any better we may be generous enough to call it charlatanry, the alternative being fraud of course. Charlatanry and Fraud

23 My second example is one which without the slightest doubt may be classified as fraud. Charlatanry and Fraud

24 An Israeli based company markets the most wonderful tools including both lie detectors and love detectors. The technique behind the lie detector is said to be something called Layered Voice Analysis (LVA). Charlatanry and Fraud

25 Here is how they claim it works every “event” that passes through the brain will leave its “finger prints” on the speech flow. LVA Technology ignores what your subject is saying, and focuses only on his brain activity. In other words, the “how” it is said is crucial and not the “what”. Charlatanry and Fraud

26 They are careful not to explicitly call the gadget “lie” detector, but there is absolutely no doubt that that is what they want us to believe it is: “LVA is capable of detecting the intention behind the lie, and by so doing can lead you in identifying and revealing the lie itself”. Charlatanry and Fraud

27 Let us have a quick look at how this product is marketed. Charlatanry and Fraud


29 The great LVA hoax




33 Charlatanry and Fraud



36 After this commercial tour let us have a look at the state of the art technology that makes all this possible. Charlatanry and Fraud

37 An examination of the description of the method in the American patent documents confirms the suspicion that the method is pure nonsense, perhaps best described as statistics based on digitization artefacts. Charlatanry and Fraud

38 The statistics is based upon what is defined as thorns and plateaus which has no relevance at all for voice analysis and is moreover dependent on how the signal is sampled. Charlatanry and Fraud

39 Now, who is the guy behind all this? Charlatanry and Fraud


41 Why is there such a flourishing market for charlatans? Why is it so relatively easy to market gadgets which one would think anyone should be able to recognize as bogus? Charlatanry and Fraud

42 I think at least a partial answer lies in how lie detectors and other wonderful tools are used in films and television series. There perfectly reliable lie detectors have been around for a long time. But crime documentaries which focus on only the most spectacular successes are also partly responsible. Charlatanry and Fraud

43 For the serious forensic speech scientist this is becoming a problem. There are two possible dangers. 1.You express yourself with the caution you know from your experience and from scientific studies is absolutely necessary, but then run the risk of being regarded as incompetent because you are unable to do what people “know” to be possible from films and TV. 2.You fall for the temptation to express yourself with a greater degree of certainty than you should. Charlatanry and Fraud

44 Gadgets like these do not deserve to be taken seriously as such, but their use in forensic investigations must be. If bogus lie detectors like the ones described here are used not just by shady private investigators, but by insurance companies, police departments and security agencies, this poses a threat that we must oppose more actively. Charlatanry and Fraud

45 Thank you for your attention! Charlatanry and Fraud

46 Other lie detection attempts Attempts have been made recently to use brain scanning methods in order to study the possibility of consistent differences in brain activity patterns which separate lie or deception from truthful statements.

47 Langleben et al. (2002) used Functional Magnetic Resonance Imaging (fMRI) to detect differences in brain activity when their subjects told a lie compared to when they told the truth. Their results indicate that: “There is a neurophysiological difference between deception and truth at the brain activation level that can be detected with fMRI”. Similar results have been obtained in other studies. Other lie detection attempts

48 High resolution thermal imaging which can detect minor regional changes in the blood flow in the face for example has also been used in an attempt to develop methods to detect lie and deception (Pavlidis and Levine, 2002). Other lie detection attempts

49 Experiments of this kind are, of course, very interesting but it seems that the people who interpret the results all make the same mistake as the Polygraph people, they tend ignore the false positives problem. Other lie detection attempts

50 What if the brain reactions that can be registered when I tell a lie are precisely the same as those that result from scratching my head or wiggling a toe? Other lie detection attempts

51 Lie detection “Unproven technologies are becoming increasingly attractive to US law enforcement and security agencies … Laboratory tools – from infrared sensors to eye trackers – are being converted into lie detectors” (Knight 2004).

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