Functional MRI-Based Lie Detection: Acknowledge Possession of the Other5

PERSPECTIVES

In one of the earliest studies, subjects NEUROSCIENCE AND THE LAW — SCIENCE AND SOCIETY were given two playing cards and were instructed to deny possession of one and Functional MRI-based lie detection: acknowledge possession of the other5. Subjects underwent fMRI scanning while they viewed a series of cards, including the scientific and societal challenges two critical cards and other cards that they had not been given. A comparison between Martha J. Farah, J. Benjamin Hutchinson, Elizabeth A. Phelps ‘truth’ trials and ‘lie’ trials revealed brain and Anthony D. Wagner activity associated with deception. In a similar task design, subjects mentally picked a Abstract | Functional MRI (fMRI)-based lie detection has been marketed as a tool number between three and eight, and when for enhancing personnel selection, strengthening national security and protecting shown a series of numbers on a screen, personal reputations, and at least three US courts have been asked to admit the denied having picked that number (the criti- results of lie detection scans as evidence during trials. How well does fMRI-based cal lie item) and also denied having picked lie detection perform, and how should the courts, and society more generally, the other numbers (truth items) while undergoing fMRI7. Here again, activity on lie respond? Here, we address various questions — some of which are based on a trials was compared with that on truth trials meta-analysis of published studies — concerning the scientific state of the art in to discover which areas were associated with fMRI-based lie detection and its legal status, and discuss broader ethical and deception in this task. societal implications. We close with three general policy recommendations. A small step towards more realistic experimental paradigms to study lying was taken by Kozel and colleagues8. They Over the centuries, human beings have and societal issues raised by this technol- devised a mock crime scenario, in which devised many different methods for the ogy. Beginning with the science, we address subjects were given a choice whether to detection of deception (BOX 1). Some are low- three questions about the current state of ‘steal’ a ring or a watch and were instructed tech — for example, the skilled recognition the art in fMRI-based lie detection. First, to place the chosen item in a locker. of facial expressions — and some are high- do current findings on lie detection, from Subsequently, they answered questions tech, including the polygraph, a device that different laboratories and using different about the ‘crime’ while in the scanner and measures autonomic arousal and is known experimental tasks, identify a consistent set were instructed to deny having taken either in popular culture as the ‘lie detector’. At of brain regions and, if so, which areas are item. In addition to lies (denials regarding present, no method of lie detection has been they? Second, how confidently can we inter- the item they took) and truthful statements proven to perform with high accuracy, and pret the results of these studies with respect (denials regarding the item they did not the search for a better method continues1. to the neural substrates of deception per se, take), subjects were asked yes-or-no general Recent efforts to detect lies have focused and what alternative interpretations have yet knowledge questions such as ‘is it 2004?’ or on measures of the brain. The appeal of this to be ruled out? Third, what additional chal- ‘do you live in the United States?’ The dif- brain-based lie detection approach is that, in lenges do we face in the effort to use fMRI ference between the lie and truth trials was contrast to most previous methods — which for the detection of deception in real-world taken to index the neural activity associated detected the emotional arousal resulting contexts? We then raise a series of issues con- with lying. Finally, researchers have com- from deception — it measures physiological cerning the ethical, legal and societal impact pared subjects’ responses when answering changes associated with cognitive processes of attempting to detect lies with fMRI. questions about past events or personal during deception and could therefore, in information, for which they were cued to principle, be detecting the process of decep- The science of fMRI-based lie detection respond truthfully or deceptively9. tion itself. Most functional imaging attempts Although fMRI-based lie detection has been In summary, for most fMRI studies of to discriminate lying from truth telling have commercialized and is used by some for lie detection, subjects are instructed by used functional MRI (fMRI), although a few real-world applications, research on this topic the researchers to lie and to tell the truth early studies used positron emission tomog- began as a form of basic science with the goal on specific trials of the experiment, and raphy, and other methods (event-related of identifying the neural systems involved the activation in lie trials and truth trials potentials and functional near-infrared spec- in deception4–6. In such studies, blood- is either directly contrasted or compared troscopy) have been applied to the related oxygen-level dependent (BOLD) activity is after contrasting each trial type to a baseline problem of detecting concealed knowledge2,3. measured under conditions in which subjects condition. The regions showing significantly Scientific and legal interest in fMRI-based are instructed or explicitly permitted to greater activation for lies than for truth are lie detection has developed rapidly. The make deceptive versus truthful responses. taken to be the neural correlates of deception. majority of scientific articles on this topic Deception has been operationalized in many have been published within the past decade, different ways in fMRI-based lie-detection Consistency of results across laboratories and there have been at least three attempts to research as well as in lie-detection research and tasks. A comparison between the decep- have fMRI-based lie detection admitted into more generally (BOX 2). The designs of these tive and truthful response task conditions US courts since 2010. studies are crucial for understanding the often results in activation in certain regions, In this Perspective article, we assess the degree to which they successfully isolate the particularly the prefrontal cortex, anterior current state of the science in fMRI-based neural correlates of deception, so several cingulate cortex and parietal cortex. How lie detection and review some of the legal examples of research tasks are given here. reliably are these regions associated with

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Box 1 | Lie-detection technology through the ages medial superior frontal cortex. As previously noted by others, there was considerable vari- Spotting a liar is hard to do. Studies have repeatedly proven this using tests in which observers ability from study to study, as no region was 58 perform barely better than if they were blindly guessing . Many different methods have been active in all (or nearly all) studies. This may devised to increase the accuracy of detecting deception. Among behavioural methods, some focus be due in part to differences in tasks and on non-verbal behaviours that are indicative of emotion, such as fleeting facial ‘microexpressions’ stimuli9, in data acquisition procedures (for (REF. 59), tone of voice60 and many other facial, vocal and bodily cues, with modest success at best61,62. Others focus on the verbal content of speech, which can reveal both emotional and example, magnet field strength and acquired cognitive concomitants of lying63. functional data resolution as well as the Functional MRI (fMRI)-based lie detection is only the most recent attempt to exploit changes in number of trials per condition and number nervous system function associated with lying as indicators of deception. The earliest methods of subjects, both of which affect statistical focused on the autonomic nervous system, and in particular on the tendency for lies to be power) and in statistical procedures (for accompanied by activation of the sympathetic nervous system (SNS). In ancient China, suspected example, choice of statistical thresholds). liars were forced to fill their mouths with dry rice and then spit it out. As sympathetic arousal Nevertheless, there is considerable agree- suppresses salivation, the rice would adhere more to the mouths of liars, who as a result would take ment across studies on which brain areas longer to spit the grains out64. In the early twentieth century, Harvard University psychology are more active during instructed lying than student and creator of Wonder Woman comics William Marston explored systolic blood pressure — another sign of SNS activation — and its relation to deception. Wonder Woman’s ‘Magic Lasso’, during truth telling. which forced its captives to tell the truth, was inspired by the blood pressure cuff65. Could the patterns documented by this The modern polygraph was based on Marston’s invention, with the addition of other measures of meta-analysis provide the scientific founda- SNS activity — namely, heart rate, respiration and perspiration. Uncertainty regarding the tion for a useful lie detector? We suggest that accuracy of polygraphy under field conditions and its dependence on examiner skills and several other empirical questions need to be attitudes1,66 had curtailed its use by the end of the twentieth century67. In the United States, it is addressed before fMRI-based lie detection outlawed for non-governmental pre-employment screening and is rarely used in court47. However, can be considered for real-world use, such to the dismay of many analysts, the polygraph nevertheless remains widely used in US national as: are the observed brain activations due 1 security employee screening . to deception per se or to confounds within The past few decades have seen efforts to develop measures of CNS activity to index deception, the experimental designs? More generally, is including scalp-recorded electroencephalography (EEG) measures and functional near-infrared spectroscopy (fNIRS). Among EEG-based methods, so‑called ‘brain fingerprinting’ uses the observed activation specific to lying or components of the event-related potential to infer whether the subject is familiar with aspects of a does it reflect something about the way lies crime that only the perpetrator would be expected to know68. Brain Electrical Oscillations are usually (but not necessarily or invari- Signature (BEOS) profiling is similarly intended to detect ‘guilty knowledge’ and has been widely ably) produced? Can fMRI discriminate used in Indian courts69, although we are not aware of any peer-reviewed studies of the method. lies from truth in individual subjects with Finally, fNIRS uses NIR light, to which the skull is relatively transparent, to measure blood sufficient accuracy to be useful in at least oxygenation and has been explored as a means of detecting CNS activity associated with lying70. some circumstances? If so, for what types of Its advantages over fMRI include price and portability; its major disadvantage is its field of view, subjects? Do laboratory-derived indicators which is limited to superficial brain regions, as well as a lower signal-to-noise ratio. generalize to the real world, in which stakes and hence emotions may be high, base rates may be unknown and subjects may attempt deception, and can one identify more specific results from a whole-brain, group analysis of countermeasures? subregions within these relatively broad ana- healthy, young adults; conducted a statistical tomical areas that are activated during decep- contrast indexing deception and reported Experimental confounds and other question? Earlier reviews of the literature found one or more foci in standardized coordinate tions of specificity. The experimental designs substantial consistency across studies10–12, but space; and reported data that had not been used in fMRI studies of deception are most the literature has continued to grow rapidly reported (in part or in full) in any other naturally described in terms such as ‘lie’ in recent years. To assess the consistency of study included in the meta-analysis (that is, and ‘truth’, and this language encourages a deception-related activity across laboratories a given dataset contributed to the analysis certain presumption of specificity. However, and tasks, we therefore carried out a new only once). Critically, the activations ana- on the basis of simple experimental contrasts meta-analysis of the fMRI-based lie-detec- lysed were group-level contrasts of deceptive between lie trials and truth trials, we cannot tion literature to date. versus truthful responding (Supplementary know what psychological processes other Like the earlier analyses of Christ et al.11 information S2 (table)). As detailed in than deception might evoke the same pat- and Wagner12, our meta-analysis used the Supplementary information S1 (box), this terns of activity. What can we conclude from activation likelihood estimation (ALE) analysis was performed over 321 foci from 28 the current literature concerning the speci- method13 (for details, see Supplementary independent statistical contrasts between lie ficity of deception-related activation? information S1 (box)). ALE quantifies the versus truth conditions that were reported in In most of the tasks used to study degree of anatomical overlap across published 23 different studies. deception with fMRI, a number of experi- neuroimaging studies that are based on peak- As shown in FIG. 1 (see also mental factors are confounded with the voxel coordinate information. This enabled Supplementary information S3 (table)), the lie-versus-truth manipulation7,12,14,15. For us to quantify the reliability of anatomical meta-analysis revealed a number of regions example, in one study16,17, BOLD activity overlap of observed activation foci rather than that were active during deception versus differed in instructed-lie versus truth trials, simply analysing commonalties in terms of truth conditions across studies at an above- but the frequency of the motor response activations that occur in pre-selected regions chance rate, including the bilateral dorso- required on truth trials was much lower of interest. Published lie-detection studies lateral and ventrolateral prefrontal cortex, than that required on lie trials. Because of were included if they: used fMRI; reported inferior parietal lobule, anterior insula and this confound, rather than reflecting neural

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Box 2 | Varieties of deception Related to these concerns about experimental confounds is the broader issue of Lying is not a single homogeneous category of behaviour9,71–73. There are lies that we tell for process (or functional) specificity. Even if personal gain or to spare the feelings of another, lies that we regard as consequential or trivial, lies it were possible to correct the memory and that we tell to others or to ourselves and lies that deceive by active assertion of a falsehood or by attention confounds inherent in the tasks mere omission of information. Each of these may have different neural correlates, depending on factors such as those discussed in the article, including the degree of rehearsal or emotion just described, there would probably remain associated with the lie9. an association between deception on the one An issue that has occupied lie-detection researchers working with polygraphy is the distinction hand and executive function and other cog- between lies elicited in different types of task74,75. In the ‘control question test’, which was nitive processes on the other hand, because developed for use with the polygraph, subjects are asked three types of question: relevant deception generally places greater demands questions (that is, questions that directly elicit the suspected lie), control questions (that is, on memory and executive functions than questions about topics that would cause most people discomfort or shame, such as childhood does truthful responding: the liar must gen- stealing or betrayal of a friend) and irrelevant questions (that is, questions that elicit innocuous erally keep two versions of events in working information such as name or birthplace). Truthful responding to the relevant questions is expected memory and must inhibit the more natural to evoke less arousal than responses to the control questions, whereas lying is expected to evoke response of responding in accordance with more arousal. In the ‘concealed information test’, also known as the ‘guilty knowledge test’, the subject is presented with correct and incorrect answers to questions about facts that only the reality. It has been noted that the regions in perpetrator of a crime would be likely to know, and so truthful subjects are assumed to show which activation is associated with deception equivalent arousal to all of the answers and deceptive subjects are assumed to show more arousal in the fMRI-based lie-detection literature to the correct answers. The functional MRI literature includes tasks that are similar to both types of are also associated with executive function, test, although the exact conditions and comparisons differ from the polygraph literature. attention and memory processes, which is consistent with the association between deception and cognitive load11,12. As many correlates of deception, critical aspects of stimuli, resulting in differential engagement have argued, it is therefore possible that these data may reflect neural responses asso- of neural mechanisms of attentional orient- fMRI-based lie detection measures dif- ciated with selecting a frequent versus an ing, and the selected stimulus may also be ferences in the engagement of these more infrequent motor action. associated with stronger or richer memo- general-purpose cognitive processes. To In an experiment with even broader ries, resulting in differential engagement the extent that deception typically (but not implications for the interpretation of exist- of neural mechanisms of memory. Are the necessarily) imposes a higher cognitive load ing fMRI-based lie-detection data, Hakun activation differences between ‘lie’ and than truth telling, it may be possible to dis- and colleagues7 carried out an experiment ‘truth’ stimuli due to the act of deception sociate the two using fMRI. Under certain in which subjects were scanned while view- or to such confounding effects of attention circumstances, true responding could tax ing a series of numbers after having chosen and memory? these processes to an equivalent or greater one in advance. In one condition, subjects The presence of memory confounds in extent than deceptive responding, a pattern were instructed to lie by responding that fMRI-based lie-detection studies was directly that has in fact been observed in at least once they had not chosen the selected number addressed in an important study by Gamer study18. Thus, despite the encouraging con- when it was shown during scanning. In a et al.14. In that study, subjects were instructed sistency revealed by the meta-analysis (FIG. 1; different condition, subjects simply viewed to encode critical items (a banknote and a Supplementary information S3 (table)), the numbers without responding during playing card) into memory, and were then truth telling could be mistakenly interpreted scanning. Strikingly, in three out of three scanned while simply viewing the critical as deception according to current methods subjects, there was greater lateral prefrontal items and control items (subjects pressed a of fMRI-based lie detection. and parietal activation in response to the button to indicate the presentation of each chosen number relative to other numbers, stimulus). Because this stimulus viewing From the laboratory to the real world both when subjects simply passively viewed task did not require subjects to respond Even if all of the uncertainties just described the numbers and when they were instructed deceptively or truthfully, differences in the could be overcome, many other issues would to lie about the chosen number7. This find- BOLD signal for critical items versus con- have to be addressed before fMRI-based lie ing suggests that in many of the studies trol items must be due to differences in the detection could be used responsibly in the in our meta-analysis, the greater activity items’ histories; that is, whether the subject real world. We turn to these issues here. observed for instructed lie stimuli may not does or does not have a memory for the reflect neural processes related to deception item. Strikingly, the results revealed greater Inferences about individual subjects. Real- but rather may reflect other cognitive dif- activation in response to the critical items world uses of lie detection will of course ferences produced by the task. For example, versus control items in the same prefrontal involve inferences about the truthfulness or the mere act of selecting a stimulus at the and anterior insular cortical areas that were deceit of individuals. What do the published outset of the experiment (whether it is previously observed in fMRI studies compar- studies tell us about the accuracy with which selecting a specific number from the range ing instructed lie versus truth trials. Because deception can be identified at the individual of three to eight or selecting a ring rather memory and attention confounds are present level? Most publications report only group than a watch from a drawer) may attach in many fMRI-based lie-detection studies, analyses, which makes them poorly suited particular significance to the stimulus that the data of Gamer et al.14, along with those of to answering this question. Of the minor- alters subsequent cognitive responses to Hakun et al.7, suggest that the consistent find- ity of studies that report statistics that are the stimulus when it appears during fMRI ings obtained in our meta-analysis may reflect directly relevant to assessing accuracy at scanning. The selected stimulus may be activation related to processes other than the level of individual subjects or indi- more salient relative to the other (‘truth’) deception per se. vidual events2,7,8,16,17,19–27, only two studies

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Lateral task, some of the participants committed MFG IFG–insula the mock crime and others did not, but all IPL were instructed to indicate that they did not. The authors were able to correctly detect deception, using fMRI, in 100% of the participants in the ‘mock crime present’ condition. However, they also mistakenly detected deception in 67% of the participants in the ‘mock crime absent’ condition. In the language of diagnostic testing, the sensitivity of m/SFG this test was high but the specificity was low. Medial Determining the real-world accuracy of a detection test also depends on a critical third factor, which is the probability of the event occurring within the population — the base rate. Indeed, the risks associated with a lie-detection test with low specificity will depend on the base rate of lying in the population assessed28,29. Imagine that the test described in REF. 22 was given to 101 people, 100 of them truthful and 1 deceptive. On Figure 1 | Results of the ALE analysis of the functional MRI ‘deception’ literature. Overlay of map the basis of the false-positive rates of Kozel of activation likelihood estimation (ALE) values (orange) on the lateral (top) and medial (bottom) and colleagues22, the test would identify 68 inflated PALS surface76, revealing regions that are consistently implicatedNature in deception Reviews |across Neuroscience studies. participants as ‘lying’ — the 1 participant The detection thresholded was set at P < 0.05, and the false-discovery rate was corrected as per the method described in REF. 13. IFG, inferior frontal gyrus; IPL, inferior parietal lobule; MFG, middle frontal who lied about the mock crime and 67 who gyrus; m/SFG, medial and superior frontal gyrus. did not. In other words, given a positive result, the probability of the test accurately indicating someone as lying is 1 in 68, or less (to our knowledge) report data relevant whether the neural correlates of deception are than 1.5%, and the likelihood of incorrectly to detecting deception at the individual- sought using univariate or multivariate analy- indicating deception when it is not present is event level. Specifically, Langleben et al.16 ses and regardless of whether the correlates over 98%. As this example illustrates, even in and Davatzikos et al.17 focused on whether are discovered by simple regression analysis or an ideal circumstance in which a laboratory instructed lie and truth events could be machine-learning algorithms. Furthermore, lie-detection test is developed and used in discriminated in the same dataset, using even high accuracy rates may decline precipi- identical situations, and is sensitive to decep- either logistic regression16 or non-linear tously when subjects use countermeasures in tion within an individual 100% of the time, machine-learning analyses17. Although these an attempt to conceal their ‘deception’ (REF. 2). its accuracy in a larger population may still event-level analyses showed accuracy rates The laboratory studies assessing the accu- be unacceptably low if the specificity of the of 78% and 88%, respectively, the impact of racy of fMRI-based lie detection on the indi- test is low and the base rate of lying is low. these early findings is limited because of the vidual-subject level assess the sensitivity and The real-world validity of fMRI-based lie above-noted response-frequency confound specificity within an individual by differenti- detection will also depend on the generaliz- in the experimental design. ating trials on which the individual is decep- ability of the findings obtained in laboratory Other studies focused on examining tive or truthful. However, determining the studies (which typically involve undergradu- whether fMRI BOLD activity differs when accuracy of a test in a general population also ate students — that is, healthy, educated an individual is lying compared to telling the requires an assessment of the test’s sensitivity young adult subjects) to the individuals truth (pooling data across events). Various and specificity across individuals within that whose veracity is to be assessed by these statistical approaches have been implemented, population: that is, what is the likelihood of methods. Consider the differences between including single-subject univariate analy- detecting deception when it is present in a criminal offenders, a group that is likely to ses2,7,19,20, univariate analyses combined with member of the population (sensitivity), and be subjected to lie-detection methods, and the counting of above-threshold voxels in what is the likelihood of correctly indicating the undergraduate students on which these targeted regions of interest8,22,25 and machine- when deception is absent (specificity)? To methods have so far been tested. A relatively learning classification2. The reported accura- date, fMRI-based lie-detection tests examin- high proportion of criminals meet the crite- cies in these individual-subject-level analyses ing accuracy within individuals have gener- ria for psychopathy, a condition that is asso- have ranged from 69% to 100%, suggesting ally not assessed the sensitivity or specificity ciated with frequent acts of deception and that these statistical approaches have prom- of the test across individuals. One exception with alterations in both structural MRI and ise. However, here again, the noted concerns is a study by Kozel and colleagues22, which fMRI studies27. A study of fMRI-based lie about attention and memory confounds tested participants who had been success- detection in criminal offenders with a diag- undermine data interpretation7,12,26. Indeed, so fully classified using the researchers’ method nosis related to psychopathy — specifically, long as studies use tasks in which the effects as ‘lying’ on a prior mock crime task (25 antisocial personality disorder — found that of deception cannot be separated from the out of 36 participants). These pre-selected a large proportion of these participants did effects of attention and memory, the prob- participants were then examined on a sec- not show typical prefrontal BOLD response lem of confounds will remain, regardless of ondary mock crime task. On this secondary patterns during instructed deception29.

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Cognitive, personality and brain factors the diminished executive control required cited earlier reporting 100% accuracy, the associated with a wide range of individual dif- as highly practiced tasks become more investigators further demonstrated that if ferences may also affect the validity of fMRI- automatic. An early fMRI study of lie detec- subjects adopt a simple countermeasure based lie detection. Structural MRI and fMRI tion found that memorized lies resulted in strategy of making imperceptible finger and changes observed with advancing age, a range less BOLD activation when compared with toe movements, accuracy fell to 33%. At pre- of psychiatric conditions (for example, schizo- unpractised lies in every deception-related sent, researchers have only begun to explore phrenia and post-traumatic stress disorder) region of interest identified except for one possible countermeasures for fMRI-based or individual traits (for example, high anxiety associated with memory retrieval9. A behav- lie detection. Preliminary data from stud- and extraversion) limit the applicability of ioural deception study showed that training ies in the laboratory of A.D.W. that focused lie-detection tests that have not been vali- on deception eliminated pre-training differ- on whether subjects can conceal memory- dated in these populations. There may also be ences in reaction times between deception related patterns of the BOLD signal also important individual differences in the neural and truth trials, which is consistent with indicate that countermeasure strategies can systems involved in deception per se that we enhanced automaticity of lying33. Outside reduce machine learning-based decoding have yet to characterize. In a clever study in the laboratory, if someone expects to be of memory states from well above chance to which participants were given the opportu- interrogated about a lie, it is very likely that chance levels39,40. nity to gain money by being dishonest, those they will rehearse and memorize the lie, In sum, even if the challenges facing fMRI who tended towards dishonesty showed an which might eliminate many of the detecta- studies of deception in the laboratory that increased BOLD signal in regions related to ble differences in the behavioural and neural were described in the previous section were cognitive control when behaving dishonestly expression of deception. met, a number of additional challenges await and when behaving honestly, whereas partici- In addition, real-world deception is likely the successful translation of this method pants who tended to be honest did not show to be highly emotional and personally rel- into the real world. The accuracy with which this pattern18. evant. Emotion could influence the neural individual subjects can be assessed when tell- circuitry of lying in two ways that might ing lies or truth and the suitability of these Differences between lies in the laboratory make it more difficult to distinguish truth accuracy rates given the base rates of lying and in real life. Another potential obstacle to from lies. First, truthfully answering ques- and truth telling in the population demand real-world lie detection is that the lies exam- tions about highly emotional events may be a major new empirical research effort. How ined in laboratory tasks are generally quite more effortful or require more (emotional) these accuracies vary as a function of an indi- unlike those that we would try to detect control and/or inhibition than truthfully vidual’s age, health, personality, life history outside the laboratory (BOX 2). Although answering questions about neutral events. To and other variables is also a crucial question researchers have been concerned with real- the extent that a lie-detection test measures and would require an even larger programme world effectiveness, and have presented non-specific brain signals of effort or inhibi- of research to be adequately addressed. Just their studies as “ecologically valid” (REF. 30) tion, it may be more likely that a true state- as differences among individuals would or “emulat[ing] as closely as possible a real ment about an emotional event is classified be expected to influence the validity of the world situation” (REF. 31), the tasks differ in as a lie (as has been found with event-related method, so too would differences in the many important ways from the situations in potentials34). However, it is also possible that nature of the lie and its context: whether which lie detection would be used in the real the emotional qualities of the event may shift the subject has lived with the lie for a long world. In the laboratory studies, subjects lie the neural signature of deception, making it time, whether the truth is more emotionally because they are instructed to, about mat- less likely that a lie will be detected. In fMRI charged than the lie and what is at stake if the ters with little personal relevance, in highly studies, emotion has been shown to alter the lie is discovered. Finally, the susceptibility of constrained and contrived situations. In neural circuitry of memory35, inhibition and fMRI-based lie detection to countermeasures addition, the familiarity of the information cognitive control36 and working memory would need to be more fully explored before being concealed and the level of emotion interference37 — all of which are processes it is applied in the real world, and this too associated with it are typically much lower in thought to underlie the differences between requires extensive research. laboratory studies than in real life. brain activity during deceptive responses Consider the situation in which a lie is versus truthful responses. Indeed, emotional Uses of fMRI-based lie detection highly rehearsed and thus familiar, and the valence has been found to affect the neural Lie detection using fMRI has moved rapidly truth is abhorrent. In this circumstance, localizations of deception-related process- from basic research in the laboratory to it seems very possible that truth telling is ing38. If a lie-detection test is developed commercial application in the real world. more effortful than lying. Evidence from based on lying about non-emotional events, In 2006, two companies began offering both fMRI and behavioural studies sug- its applicability to assessing deception con- fMRI-based lie detection services: No Lie gests that practice or rehearsal may alter the cerning emotional or important, personally MRI, based on the method developed by neural signature of deception. As indicated relevant events may be limited. Langleben and colleagues at the University in FIG. 1, some of the regions commonly of Pennsylvania (Philadelphia, USA), and activated in fMRI studies of lie detection Countermeasures. Methods of lie detection Cephos, based on the method of Kozel include prefrontal regions that have been inevitably spawn methods designed to evade and colleagues at the University of Texas at proposed to underlie cognitive functions detection, so the mere possibility of counter- Dallas (USA). These companies have sug- required during the more effortful ‘lie’ con- measures should not be grounds for rejec- gested a number of uses for fMRI-based dition. Studies examining practice effects tion of fMRI-based lie detection. However, lie detection, spanning business, family across a number of cognitive tasks routinely the ease and success of countermeasures life, criminal justice and national security show diminished activation in the prefrontal are relevant to the real-world usefulness of contexts. For example, No Lie MRI recom- cortex32. This reduction is thought to reflect fMRI-based lie detection. In the one study mends its services for diverse problems,

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ranging from combating insurance fraud intentionally violate the law and sought to criteria, which were developed in legal (http://www.noliemri.com/customers/ present the results of fMRI-based lie detec- cases that involved scientific evidence other GroupOrCorporate.htm) and increas- tion as evidence that his testimony was than fMRI-based lie detection, for deciding ing public trust of US and foreign leaders truthful. A hearing was held in Memphis when a method has sufficient validation: (http://www.noliemri.com/customers/ Federal Court, before a Magistrate Judge to namely, the Frye and Daubert criteria. Government.htm) to “risk reduction in dat- whom had been delegated the task of mak- These criteria exemplify the interdepend- ing” (http://www.noliemri.com/customers/ ing a recommendation on admissibility — ence and the independence of scientific Individuals.htm). that is, to determine whether fMRI-based and societal decision making. Although The potential application of fMRI-based lie detection meets the Daubert criteria. scientific research provides essential input lie detection that has received the greatest The 39‑page opinion included the recom- into decisions regarding admissibility, public scrutiny has been for assessing the mendation (later accepted by the presiding the decisions themselves are not made by truthfulness of legal testimony. In at least district judge) that the fMRI evidence be the kinds of conventional scientific crite- three cases, US courts have been asked to excluded. The analysis noted: the lack of ria applied, for example, by reviewers of admit evidence from fMRI-based lie detec- general acceptance for the method within research articles. It is fair to say that, in tion. The courts determine admissibility the scientific community; the substantial some respects, legal standards may be lower of scientific evidence by applying one of differences between laboratory research than scientific standards where scientific two standards, depending on jurisdiction. designs and the real-world use of fMRI- evidence such as fMRI-based lie detec- Both standards are designed to keep ‘junk based lie detection in this case; the lack tion is concerned. As argued by Schauer46, science’ from influencing jury decisions, of ‘real-life’ error rates; and the lack of the societal needs served by the law often although they do so in different ways. suitably controlling standards for the use require a more pragmatic approach to According to the Frye standard, set forth in of the method. (The latter determination the vetting of scientific evidence. In the Frye v. United States in 1923 (REF. 41), admis- was prompted by Cephos’s discounting of absence of better methods of discovering sibility hinges on the general acceptance of one of three scanning sessions, which had the truth, an imperfect method may be the method within its particular scientific indicated deception, on the grounds that better than nothing: “… the exclusion of field. According to the Daubert standard, the defendant was fatigued.) However, the substandard science, when measured by set forth in 1993 by the US Supreme Court opinion also observes that precise valida- scientific standards, may have the perverse in Daubert v. Merrell Dow 42, judges in fed- tion in real-world contexts, of the sort effect of lowering the accuracy and rigor of eral cases must be more active gate-keepers that scientists might require in their own legal fact-finding, because the exclusion of of scientific evidence in court rather than research, is not always legally necessary: “in flawed science will only increase the impor- simply deferring to general scientific opin- the future, should fMRI-based lie detection tance of the even more flawed non-science ion. In doing so, they should take five fac- undergo further testing, development, and that now dominates legal fact-finding.” tors (among others that they may consider peer review, improve upon standards con- (REF. 46). As Langleben and Moriarity have relevant) into account when making their trolling the technique’s operation, and gain noted47, this reasoning can be extended to decisions: whether the method is testable and acceptance by the scientific community for other scientific methods as well, given that has been tested; whether it has been reported use in the real world, this methodology may many of the methods of forensic science in peer-reviewed publications; whether there be found to be admissible even if the error have been found wanting48. is a known or potentially knowable error rate is not able to be quantified in a real As scientists, we are not accustomed rate; whether there are standards for the way world setting.” (REF. 44). to endorsing methods on the grounds in which the method is used; and finally, In the case of Smith v. State of Maryland45, that they are ‘lesser evils’. The difference as in Frye, whether the method is gener- the defendant was being retried for second- between the scientific and legal approach ally accepted within the relevant scientific degree murder in 2012 and sought to to accepting questionable sources of evi- community. introduce evidence of the truthfulness of dence rests in part on the scientist’s choice The first two attempts to introduce fMRI- his own testimony from No Lie MRI. The of hypotheses to test. If no good method based lie detection occurred in 2010. In the judge refused to admit the evidence on the is available to test a particular hypothesis, first case, Wilson v. Corestaff Services43, the basis of the Frye standard, after concluding then a scientist will normally simply decline plaintiff in an employment discrimination that experts in the field (including A.D.W. to test it. The legal system cannot make case sought to introduce evidence gathered and E.A.P) did not agree with the com- the analogous decision; the question of by Cephos to support the credibility of a wit- pany’s experts, suggesting lack of ‘general ‘guilt beyond a reasonable doubt’ must be ness’s testimony. The judge in this case ruled acceptance’. addressed with the evidence available, even the evidence inadmissible on the grounds that when that evidence is acknowledged to credibility assessment is the job of the jury Legal, social and ethical issues have serious weaknesses. but also noted that the method would not Science can, in principle, tell us the accu- What about societal decision making meet the Frye criteria, stating: “even a cursory racy of fMRI-based lie detection for any regarding potential uses of fMRI-based lie review of the scientific literature demonstrates particular population of individuals under detection outside the courtroom? The world that the plaintiff is unable to establish that the any particular circumstances that we might has only begun to engage with the question use of the fMRI test to determine truthfulness specify. It cannot, however, tell us how of how best to use, and limit the use of, fMRI- or deceit is accepted as reliable in the relevant accurate fMRI-based lie detection should based lie detection. Questions concerning the scientific community” (REF. 43). be for any particular use to which it might necessary degrees of accuracy and validity In the second case, United States v. be put. That decision depends on the needs will undoubtedly require different answers Semrau44, the defendant standing trial for and values of the people using the method. for different tasks in different contexts, Medicare fraud claimed that he did not We have seen that the US legal system has according to the potential benefits of correct

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lie detection, the costs of wrong calls and the relation to the occasional correct identifica- constitute another aspect of societal manage- intersection of this technology with moral tion. As with other questions concerning ment that arises regardless of the method’s principles such as the right to privacy. requirements for accuracy, the question known accuracy. At present, when the meth- of how many individuals we are willing to od’s accuracy in the real world is unknown How accurate is accurate enough? The most falsely accuse of deception for the sake of an and even laboratory accuracy estimates are immediate ethical and social issues raised occasional correctly identified liar will be unavailable for subjects of different ages and by fMRI-based lie detection arise because determined not by research but by society’s states of health, subjects must understand the of the method’s lack of demonstrated accu- needs and values. questionable accuracy of the method in order racy and validity. Given the scientific and to make an informed decision on their own technical problems reviewed earlier, the Ethical issues beyond validity and accuracy. behalf. They must also understand that not all most likely harms would result from false Not all ethical issues surrounding fMRI- outside parties will interpret the results of the determinations — lies wrongly identified based lie detection depend on the method’s test with appropriate caution. In the future, as truths and truthful statements wrongly accuracy; even a technically perfect lie detec- when the method may become more accu- identified as lies. Some commentators have tor would raise ethical issues and be subject rate, subjects should still be informed that the suggested a ban or moratorium on fMRI- to societal deliberation and regulation. method is not perfect. Consent is especially based lie detection pending better evidence Indeed, some issues would become more fraught when testing is not requested by the concerning its accuracy49,50. The history of pressing in the event of successful fMRI- subject but by another party, such as the gov- polygraphy offers tragic reminders of the based lie detection. ernment, an employer or a jealous spouse. cost, to national security and human life, of Lie detection using fMRI raises privacy Additional safeguards may be needed to pre- over-reliance on an apparently high-tech but issues that require societal control, much vent coercion, including the indirect coercion inaccurate method for detecting deception. as we place limits on other practices that that results when refusal to take the test is In two well-known examples of the poly- intrude on privacy, from DNA collection seen as indicative of guilt. graph’s false-negative results, the American to wire tapping. For example, if everyone’s In sum, the question of whether and how CIA (Central Intelligence Agency) agent phone conversations and e‑mail messages to use fMRI-based lie detection cannot be Aldrich Ames and the Jordanian CIA were generally available to their families, answered solely on the basis of the method’s informant Humam Khalil Abu-Mulal al‑Bal- employers and the state, and if the DNA of performance. No method will ever be known awi both passed polygraph testing (twice in all citizens were on file with law enforcement to have 100% accuracy for any context in the case of Ames), even though Ames spent authorities, much crime and misbehaviour which it might be deployed. Deciding what years selling American secrets to the Soviets would be discovered or, better still, averted. level of uncertainty is acceptable depends on and Russians, and al‑Balawi killed seven CIA But societies place limits on the collec- how different kinds of outcomes are valued. agents as a double agent. False-positive poly- tion and use of such information in order Correct and incorrect identifications of lies graph results have cost honest people job to protect personal privacy. An additional and of truth may be weighted very differently opportunities and even their liberty, such as reason to limit access to such information under different circumstances and in differ- when they led to false confessions51. is to increase the benefit it provides to those ent societies. For example, the priority placed Marks52 has pointed out that the impres- in possession of it. Societal management of on outcomes related to security relative to the sive visual appearance of fMRI-based lie fMRI-based lie detection would presumably rights of individuals will determine whether detection results may eclipse concerns be aimed at balancing the cost to individual it is worse to miss a liar or to falsely accuse about the method’s technical weaknesses, privacy against the collective benefits of an honest person. The strength of a society’s including the likelihood of false positives. reduced crime and terrorism, enhanced per- commitments to principles including indi- He suggests that government agents inter- sonnel selection and the generally increased vidual privacy, autonomy and freedom will rogating detainees would naturally tend to honesty between people that might result also shape its policies concerning fMRI-based increase the aggressiveness of their tactics from the knowledge that the veracity of one’s lie detection. if a detainee’s fMRI scan indicates decep- statements could be tested. tion. Thus, although lie-detection methods In the United States, the legal framework Policy recommendations might be thought to reduce the use of harsh for the protection of privacy includes the How should the development and use of interrogation, they might in fact be used to Fourth and Fifth Amendments to the US fMRI-based lie detection be managed in light justify abusive treatment of detainees, a par- Constitution, which several legal scholars of the scientific, legal, ethical and societal ticularly deplorable outcome in the case of have discussed in relation to fMRI-based lie issues just reviewed? We offer three general false-positive results52. detection and other forms of brain imaging recommendations. As noted earlier, false positives in fMRI- that provide psychological information53–55. First, different policies should be consid- based lie detection will have the greatest The Fourth Amendment protects against ered for different applications of fMRI-based negative impact when the method is used to warrantless search, including physical tests lie detection. We do not join calls to ban identify relatively rare cases of dishonesty in such as fMRI. The Fifth Amendment pro- fMRI-based lie detection across the board. a population. When applied to large num- tects against compelled self-incriminating Despite the enormous shortcomings of the bers of mostly honest people, even mod- testimony. It remains to be decided whether current evidence, reviewed above, we sug- est false-positive rates will result in many fMRI-based lie detection should be viewed gest that restrictions should be proportional wrongly accused individuals. Applications as physical evidence or testimony56. to the outcomes and principles at stake. Risk such as the routine screening of job appli- Considerations of individual autonomy reduction in dating calls for different stand- cants or travellers are therefore problem- and freedom arise in connection with the ards of certainty and different protections of atic, as they would probably result in large process of consenting to undergo fMRI-based individual rights than the interrogation of numbers of falsely accused individuals in lie detection. Consent procedures therefore terrorist suspects.

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69. Aggarwal, N. K. Neuroimaging, culture, and forensic 75. Ben-Shakhar, G., Bar-Hillel, M. & Kremnitzer, M. Trial official views of either the John D. and Catherine T. psychiatry. J. Am. Acad. Psychiat Law 37, 239–244 by polygraph: reconsidering the use of the guilty MacArthur Foundation or the MacArthur Foundation (2009). knowledge technique in court. Law Hum. Behav. 26, Research Network on Law and Neuroscience. 70. Tian, F., Sharma, V., Kozel, F. A. & Liu, H. Functional 527–541 (2002). near-infrared spectroscopy to investigate 76. Van Essen, D. C. A population-average, landmark- and Competing interests statement hemodynamic responses to deception in the prefrontal surface-based (PALS) atlas of the human cerebral The authors declare no competing interests. cortex. Brain Res. 1303, 120–130 (2009). cortex. Neuroimage 28, 635–662 (2005). 71. Bok, S. Lying: Moral Choice in Public and Private Life FURTHER INFORMATION (Random House Digital, 2011). Acknowledgements Nature Reviews Neuroscience Series on Neuroscience and 72. Barnes, J. A. A Pack of Lies: Towards a Sociology of The authors thank O. Jones for guidance on the legal issues the law: http://www.nature.com/nrn/series/neurosciencelaw/ Lying (Cambridge Univ. Press, 1994). discussed herein, and T. Chow for assistance with the meta- index.html 73. DePaulo, B. M., Kashy, D. A., Kirkendol, S. E., analysis. They gratefully acknowledge the support of the Law Neurolaw.org: http://neurolaw.org/ Wyer, M. M. & Epstein, J. A. Lying in everyday life. and Neuroscience Project, which is funded by the John D. J. Pers. Soc. Psychol. 70, 979–995 (1996). and Catherine T. MacArthur Foundation. The writing of this SUPPLEMENTARY INFORMATION 74. Lykken, D. T. Why (some) Americans believe in the lie article was partially supported by the US National Institutes See online article: S1 (box) | S2 (table) | S3 (table) detector while others believe in the guilty knowledge of Health grant R01‑HD055689. This article reflects the ALL LINKS ARE ACTIVE IN THE ONLINE PDF test. Integr. Physiol. Behav. Sci. 26, 214–222 (1991). views of the authors and does not necessarily represent the

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