Brain scans could influence jurors more than other forms of evidence

It's surely just a matter of time until functional MRI brain scans are admitted in US and UK courts. Companies like No Lie MRI have appeared, and there have been at least two recent attempts by lawyers in the USA to submit fMRI-based brain imaging scans as trial evidence.

Functional MRI gauges fluctuating activity levels across the brain, with experts divided on the merits of using the technology as a high-tech lie detection measure (see earlier). The late David McCabe who died earlier this year, and his colleagues, have put that debate to one side. They asked: if fMRI evidence were to be allowed in courts, would it have a particularly influential effect on jurors' decisions? There's good reason to think it might. For example, a 2008 study by Deena Weisberg found that lay people and neuroscience students (but not neuroscience experts) were more satisfied by bad scientific explanations when they contained gratuitous mentions of neuroscience.

For the new study, 330 undergrads at Colorado State University read a vignette about a criminal trial in which a defendant was accused of killing his estranged wife and lover. Various points of evidence were mentioned and summaries of testimony and cross-examination were provided (the vignette amounted to two pages).

Crucially, a sub-set of the participants read a version in which fMRI evidence was cited: "... there was increased activation of frontal brain areas when Givens [the defendant] denied killing his wife and neighbour, as compared to when he truthfully answered questions." For comparison, other participants read a version that either included incriminating evidence from polygraph, from thermal imaging technology (which measures changes in facial skin temperature), or that contained no lie-detection technology.

The key finding was that participants who read the brain-imaging version were far more likely (76 per cent) to say they considered the defendant guilty, compared with participants who read the other versions (47 to 53 per cent). Moreover, the lie-detection evidence was more likely to be cited by participants in the fMRI condition as key to their decision, as compared with participants who read versions that didn't mention fMRI.

The participants were not entirely seduced by fMRI. Some of them were given a slightly different version of the fMRI vignette, in which the expert witness warned about the technology's unreliability. These participants came to a similar proportion of guilty verdicts as the participants who read the vignette versions that lacked fMRI evidence. So it seems the persuasive influence of fMRI evidence can be tempered easily enough if people are reminded of its limitations.

The researchers acknowledged the obvious weaknesses of their study: the use of students as mock jurors, the use of vignettes rather than a real trial, and so on. These caveats aside, they said their data show that fMRI evidence could be more influential than other types of evidence. "... [T]hough determining whether that indicates the evidence would lead to unfair prejudice, confusion of the issues, misleading the jury, or needless presentation of cumulative evidence is a complex issue," they said. "At the very least, it appears that juries should be informed of the limitations of fMRI evidence."
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McCabe, D., Castel, A., and Rhodes, M. (2011). The Influence of fMRI Lie Detection Evidence on Juror Decision-Making. Behavioral Sciences and the Law DOI: 10.1002/bsl.993

Further reading: The brain on the stand, by Jeffrey Rosen, New York Times magazine.

This post was written by Christian Jarrett for the BPS Research Digest.

Childhood self-control linked with multiple outcomes at age 32

Psychologists have provided a dramatic demonstration of how a person's childhood levels of self-control are linked with outcomes later on in their life. This is important because unlike other traits that are associated with life outcomes - including cleverness, tallness, and beauty - lots of research suggests that self-control is readily amenable to improvement through training.

Terrie Moffitt and her team assessed the self-control of 1000 New Zealand children at the ages of 3, 5, 7, 9 and 11 and then interviewed them when they'd reached the age of 32. The striking finding was that the study participants with poor childhood self-control were more likely in adulthood to have children of their own in a one-parent situation, more likely to have credit and health problems and more likely to have been convicted of a criminal offence, even after factoring out the effects of intelligence and social class. These associations held, albeit to a far weaker extent, even when restricting the analysis to self-control scores obtained at age 3.

To flesh out some examples, the top fifth of the sample in terms of childhood self-control had rates of serious adult health problems at 11 per cent versus 27 per cent for the bottom fifth of the sample. The crime rates in adulthood were 13 per cent for those high in childhood self-control versus 43 per cent for those with low childhood self-control.

The relationship with adult outcomes held across the full-range of childhood self-control scores. In other words, there doesn't appear to be a level of self-control beyond which no more benefits are gleaned. Neither is there a nadir of self-control beneath which no further costs are incurred.

There was also evidence in the data for what the researchers called adolescent "snares" that trapped individuals in harmful lifestyles. For example, children with lower self-control were more likely to smoke in adolescence, to leave school with no qualifications and to become a teenage parent. In turn these teenage "snares" predicted the chances in adulthood of having poor health, financial problems or being a criminal.

Moffitt and her colleagues said their results strengthened the case for introducing self-control enhancement interventions in both childhood and adolescence in what they called a "one-two punch". "... [I]nterventions in adolescence that prevent or ameliorate the consequences of teenagers' mistakes might go far to improve the health, wealth and public safety of the population," they said. "On the other hand, that childhood self-control predicts adolescents' mistakes implies that early childhood intervention could prevent them."

Because the link between childhood self-control and adult outcomes held across the full range of self-control scores, the researchers further recommended introducing universal, rather than targeted, intervention programmes - doing so would help reduce stigma, they said, and could provide benefits even to those who already score highly in self-control.

This study chimes with Walter Mischel's findings when he tracked down the participants from his classic marshmallow research. Those young children who were better able to resist the allure of a cookie or marshmallow grew into teenagers with fewer disciplinary problems and better school results.
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Moffitt, T., Arseneault, L., Belsky, D., Dickson, N., Hancox, R., Harrington, H., Houts, R., Poulton, R., Roberts, B., Ross, S., Sears, M., Thomson, W., and Caspi, A. (2011). From the Cover: A gradient of childhood self-control predicts health, wealth, and public safety. Proceedings of the National Academy of Sciences, 108 (7), 2693-2698 DOI: 10.1073/pnas.1010076108

This post was written by Christian Jarrett for the BPS Research Digest.

Does a murderer's crime-scene behaviour echo his criminal history?

In the old days of criminal profiling, a psychologist would study the idiosyncrasies of a crime scene with the expert-eye of an art collector inspecting a painting of unknown provenance. They'd draw on their clinical and forensic knowledge to help the police narrow their search, describing to them the kind of person who would likely commit a crime in this way. It wasn't particularly scientific and there were some high profile blunders, such as the misguided entrapment of Colin Stagg during the hunt for the killer of Rachel Nickell.

By contrast, contemporary criminal profiling is more data-driven. More about number crunching and less about the judgment of a single expert. Thousands of criminal records are pored over to look for factual correlations that could usefully inform investigations. It's been shown for example, that two burglaries closer together geographically, or closer together in time, are more likely to have been committed by the same person.

This empirical approach is also being brought to bear on more psychological aspects of crime scenes. In a new study, Carrie Trojan and Gabrielle Salfati studied a set of criminal records to see if there were links between the crime scene behaviour of murderers and the general theme of their offending history. The majority of murderers in the USA, where this research was conducted, have an existing criminal record, so if such a link could be established it could help guide future murder hunts.

The researchers' prediction was that murder scenes betraying signs of uncontrolled violence and impulsivity, which they labelled as 'hostile', will be more likely to have been perpetrated by a person with a record of committing crimes bearing that same hall-mark, such as assault, domestic violence and vandalism. By contrast, they predicted that murder scenes betraying signs of calculation and an ulterior motive, which they labelled 'cognitive', such as hiding the body, and involving acts of a sexual nature or robbery, will be more likely to have been committed by someone with a criminal record involving more considered, 'instrumental' crimes, such as theft or evasion of arrest.

Trojan and Salfati obtained records from the Cincinnati Police Department of 122 murders committed by someone who'd only ever killed once (between 1997 and 2006), and records of nine serial killers from across the USA. The latter had killed between three and six people each, but only ever one person at a time. The researchers first established that it was possible to classify the majority of murder scenes as either hostile or cognitive based on a scene having twice as many signs of one theme, in proportionate terms, than the other. On this basis, 87 per cent of the murder scenes were considered to have a dominant theme.

Next, the researchers showed that the vast majority (95 per cent) of murders by a one-victim killer were associated with hostile murder scenes. This chimes with the fact that nearly half of all murders in the USA occur during arguments. In contrast, the murder scenes left by serial killers were approximately half the time (51 per cent) hostile themed, and half the time (49 per cent) cognitive themed.

Turning to the key question of whether murder scene behaviour echoes the murderer's criminal history, the results unfortunately became far messier. For murderers with one victim, the most common pattern (26 per cent) was for a hostile crime scene to be left by a person with a history of more instrumental crimes. In other words, there was most often actually a mismatch between murder scene behaviour and offending history. For 24 per cent of single-victim murderers, their was a hostile/hostile match in the murder scene and offending history. For the remainder, the classifications were mixed or unidentifiable.

What about the serial killers? Although the largest category (33 per cent) did show a murder scene/ offending history match - being more cognitive and instrumental in each case - other patterns were also found, with 22 per cent tending to leave a mixture of cognitive and hostile murder scenes, but with an instrumental offending background, and another 22 per cent leaving a mixture of murder scenes and having a mixed background of offending.

'When linking criminal history to crime scene behaviour, thematic consistency was not evident in most cases,' the researchers concluded. 'Essentially, the results show that most single-victim homicide crime scenes display the same theme and that offenders are equally likely to have a pattern of either violence or instrumentality in their criminal background and a decent number have no pattern in their criminal history …' And here's the rub, Trojan and Salfati added: 'It would be difficult to apply this information in investigations.'

The study had its limitations. Not only was the number of serial killers woefully small, but as the researchers themselves concede, they didn't look at the time-line of murderers' past offences. This could have revealed useful patterns, such as that it is a murderer's recent style of offending that is linked to his or her murder scene behaviour, rather than his or her overall career pattern of offending. 'However,' the researchers said, 'because this study was the first to directly focus on the link between criminal history and crime scene actions, it provides an important first step for more in-depth examinations.'
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Trojan, C., and Salfati, C. (2011). Linking Criminal History to Crime Scene Behavior in Single-Victim and Serial Homicide: Implications for Offender Profiling Research. Homicide Studies, 15 (1), 3-31 DOI: 10.1177/1088767910397281

How to cheat a brain-scan-based lie detector

Cheating the scanner is relatively easy

Sure, it's possible to differentiate patterns of truth-telling brain activity from patterns of lying-related activity. But contrary to media hype, experts have been quick to point out that the accuracy of brain-scan based lie detection is often no better than with traditional approaches, such as the polygraph. Furthermore, these experts warn, brain-scan methods could, in theory, be easily thwarted by liars with even modest levels of guile. That claim is no longer purely theoretical, for in a new study, Girgio Ganis and his colleagues have used a popular paradigm to show just how easy it is for lying participants to trick the brain-scanner.

Twenty-six participants had their brains scanned whilst they looked at the same six dates appearing for half a second each, one at a time, on a screen. For each date they had to indicate with a button press whether it was their date of birth - yes or no. This was repeated several times. In the truth-telling condition, none of the dates was their birth date and the participants simply told the truth and said 'no' to each date. In the lying condition, one of the dates was their birth date and their task was to lie and indicate 'no' whenever it appeared. An equivalent set-up in a real-life criminal case might involve a suspect repeatedly looking at the same selection of knives and indicating whether they owned any of them. One further twist to the task was that participants had to look out for a further specific meaningless date - this was just to make sure they stayed engaged with the task.

When the participants lied and pressed 'no' whenever their birth date was visible then, consistent with past research, their mendacity was revealed in their brain activity. In particular, because of its salience, seeing one's birth date was associated with raised activity in the front-most part of the brain, on both sides. Focusing on activity in these regions, a simple algorithm could tell whether a participant was lying or not with 100 per cent accuracy (the extremely high accuracy may be due to the greater salience of one's own birth date compared with the material used in previous research).

Most importantly, in a repeat of the experiment, the participants were taught a simple cheating technique. All they had to do was ever so slightly move their left index finger, middle left finger, and left toe, respectively, whenever three of the irrelevant dates appeared on the screen (they were instructed to ensure the movements would be too slight to be seen by someone watching). This cheating strategy lent salience to these irrelevant dates, thereby reduced the stand-out salience of one's birth date, and had the effect of reducing the accuracy of the lie-detection algorithm to 33 per cent. In other words, most instances of lying were misidentified as honest responses.

The researchers think that the moving part of this cheating strategy probably isn't necessary. For example, deliberately recalling a certain memory when certain 'irrelevant' stimuli are shown would have the same effect of reducing the stand-out salience of a target stimulus, be that a murder weapon or a date of birth.

'Although these results apply directly only to the specific [and commonly used] laboratory paradigm used here ...,' the researchers said, 'they support the more general point that the vulnerability of the neuroimaging paradigms for deception detection to various countermeasures should be assessed and documented explicitly before they can be used in applied settings.'
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Ganis G, Rosenfeld JP, Meixner J, Kievit RA, and Schendan HE (2011). Lying in the scanner: Covert countermeasures disrupt deception detection by functional magnetic resonance imaging. NeuroImage, 55 (1), 312-9 PMID: 21111834

How reliable is our memory for our own previous intentions

Why did I buy this?

The fallibility of eye-witness memory is well documented. But what about people's memories of their own past intentions? This is an unexplored issue in memory research with real-life implications.

Consider the copyright infringement case in 2002, in which French composer Jacques Loussier sued Eminem, claiming that the track Kill You sampled beats from Loussier's work. Loussier further claimed that the success of the album was due in large part to the popularity of that specific track. Eminem's team responded by conducting a survey of people who'd bought the album in the last three years, only one per cent of whom stated they'd bought the album for the specific song Kill You.

The survey appeared to undermine Loussier's claim, but the trouble is that without any research on the topic, we don't know whether those survey responses can be trusted. Now a team led by Suzanne Kaasa and including Elizabeth Loftus has made a start on plugging this gap in the literature.

Nearly six hundred undergrads answered open-ended questions about why they'd purchased, downloaded or copied their most recently acquired album (the vast majority had acquired one within the last two weeks), and then they provided the same information again six months to a year later. The participants' answers fell into five main categories: because they liked the artist, liked the music, liked a specific song or songs, someone had recommended the album, or they needed the album for a specific purpose.

The key finding was that only one in five participants gave a consistent reason or reasons at both time points. The researchers had anticipated that memory for some reasons might prove more durable over time than others, but this wasn't the case. Overall, the most common form of change was simply to invent new reasons at the later time point. Sometimes participants also forgot reasons they'd mentioned earlier. Unsurprisingly perhaps, participants who recalled more reasons at the first time point tended to be more prone to forgetting reasons when quizzed again later. This was also true of participants who reported liking their CD more, perhaps because they'd felt less need to dwell on their motives at the time they acquired the album.

A subset of 82 of the participants also gave their reasons at a third time point, approximately six months to a year after the second time of questioning. Although still evident, changes in memory between the second and third time points were far reduced compared with between the first and second time points. This is important for real-life legal situations because consistency of answers across later interviews could be interpreted as a sign of memory reliability. 'It appears critical to have an accurate and complete record of the very first interview given by a witness,' the researchers said.

The study had some limitations, including the fact that the precise time between album acquisition and the first questioning session was unknown. However, the researchers observed that 'although individuals may not be able to accurately recall the reasons for their behaviours ... the real world continues to rely on self-reported motivations in a variety of circumstances, including police investigations and court proceedings.'
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Kaasa, S., Morris, E., and Loftus, E. (2011). Remembering why: Can people consistently recall reasons for their behaviour? Applied Cognitive Psychology, 25 (1), 35-42 DOI: 10.1002/acp.1639

Shock result! Asking children and teenagers to promise to tell the truth actually works

When teenagers are asked to provide testimonies for use in court, how do you increase the likelihood that they'll tell the truth? It may sound twee, but a North American study claims that merely asking them to promise to tell the truth can be surprisingly effective.

Angela Evans and Kang Lee had just over one hundred 8- to 16-year-olds complete a 10-item trivia test, which unbeknown to the youngsters featured two impossible questions ('Who invented the hair brush?' and 'Who discovered Tunisia?'). A little entrapment never hurt anyone: the participants were promised a $10 reward if they got all 10 answers right and told to refrain from peeking at the answers located on the inside of the testing booklet. For 54 per cent of the sample, the temptation proved too great and hidden cameras caught them peeking.

Next, the youths were interviewed. 'While I was out of the room, did you peek at any of the answers?' an experimenter asked. Eighty-four per cent of the peekers lied and said they hadn't peeked. Next they answered some questions about their understanding of truth and lying and the morality of dishonesty. Finally, all the participants were asked to promise to tell the truth in answer to the next question. This was a repeat of the question about whether they'd peeked at the answers. This time just 65 per cent lied - a statistically significant improvement.

Of course this first study doesn't show that the promise to tell the truth was the active ingredient in reducing lying - perhaps it was the discussion about morality or merely the act of being asked the same question twice. A second experiment with another forty-one 8- to 16-year-olds was identical to the first except the bit about promising to tell the truth was omitted. They still had the morality discussion and they were again asked twice whether they had peeked at the answers. Eighty-two per cent of peekers lied when first asked if they'd peeked. When asked again after the morality questions, 79 per cent still lied - no change in terms of statistical significance.

The lying youngsters in the first experiment who were asked to promise to tell the truth were eight times as likely to switch from lying to truth-telling than were the liars in the second experiment. 'When conducting forensic interviews with child and adolescent witnesses, police officers, social workers, and lawyers could use the honesty-promoting technique of promising to tell the truth,' the researchers said. 'In turn, the likelihood of obtaining truthful statements may increase.'
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Evans AD, and Lee K (2010). Promising to tell the truth makes 8- to 16-year-olds more honest. Behavioral sciences and the law PMID: 20878877

Hunting the successful psychopath

Put aside the dramatic Hollywood portrayals. Suited, married, high achieving, some of them walk among us. No, not vampires or super-heroes but 'successful psychopaths'. Like their criminally violent cousins - the standard psychopaths - these people are ruthless, callous, fearless and arrogant. But thanks to their superior self-control and conscientiousness, rather than landing in prison, they end up as company chief executives, university chancellors and Queen's Council barristers. Well, that's the idea anyway. But it's an idea that's proven difficult for psychologists to investigate. After all, if you advertise for volunteers for a study of successful people who are psychopathic, you're not likely to get many responses.

Stephanie Mullins-Sweatt and her collaborators tried a different tack. They surveyed hundreds of members of the American Psychological Association's Division 41 (psychology and law), criminal attorneys and professors of clinical psychology about whether they'd ever known personally an individual who was successful in their endeavours and who also matched Hare's definition of a psychopath: 'social predators who charm, manipulate and ruthlessly plow their way through life ... completely lacking in conscience and feeling for others, they selfishly take what they want and do as they please, violating social norms and expectations without the slightest sense of guilt or regret.'

Of the 118 APA members, 31 attorneys and 58 psychology professors who replied, 81, 25 and 41, respectively, said they'd previously known a successful psycho. The examples given were predominantly male and included current or former students, colleagues, clients, and friends (sample descriptions here). The survey respondents were asked to rate the personality of the successful psychopath they'd known and to complete a psychopathy measure of that person. These ratings were then compared with the typical profile for a standard (unsuccessful) psychopath.

The key difference between successful and standard psychopaths seemed to be in conscientiousness. Providing some rare, concrete support for the 'successful psychopath' concept, the individuals described by the survey respondents were the same as prototypical psychopaths in all regards except they lacked the irresponsibility, impulsivity and negligence and instead scored highly on competence, order, achievement striving and self-discipline.

'The current study used informant descriptions to provide information about successful psychopaths,' the researchers concluded. 'Such persons have been described in papers and texts on psychopathy but only anecdotally. This was the first study to conduct a systematic, quantitative analysis of such persons.'
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Mullins-Sweatt, S., Glover, N., Derefinko, K., Miller, J., & Widiger, T. (2010). The search for the successful psychopath. Journal of Research in Personality, 44 (4), 554-558 DOI: 10.1016/j.jrp.2010.05.010

Predicting when a crime is about to take place on CCTV

Are experienced CCTV operators better than naive participants at judging from an unfolding scene on CCTV whether or not a crime is about to be committed? The short answer is no, they aren't. Presented with 24 real-life 15-second CCTV clips, and asked to predict which half ended just before a crime was about to be committed (examples included violence and vandalism) and which half were innocuous, 12 experienced CCTV operators managed just 55.5 per cent accuracy - no better than if they'd just been guessing. Twelve naive controls achieved an accuracy of just 46.5 per cent - no worse, in terms of statistical significance, than the CCTV operators.

Another purpose of the research was to find out if certain viewing tactics lead to more accurate predictions of criminality. To do this, Dawn Grant and David Williams of the University of Hertfordshire recorded the eye movements of the CCTV operators and control participants as they watched the brief clips. Also, for a subset of the clips, they asked the participants to talk through their thought processes regarding what was taking place.

The key to successful predictions seemed to be to pay attention to the social context. Specifically, when participants spent more time focused on the face or head of single individuals not engaged in any social interaction, or looking at the bodies of those in a social interaction, they tended to more accurately predict whether a crime was about to occur. Grant and Williams think this might be because the former allowed the participants to notice when a lone person in the scene was staring at other people, which could betray their plans to commit a criminal act. Meanwhile, viewing the bodies, rather than faces, of those in a social interaction, might have allowed the participants to notice aggressive body language and the spatial proximity of people in a group.

This speculation was backed up by the participants' spoken accounts of how they were appraising the scenes. For example, participants who made accurate comments about which people in a scene belonged to which social group tended to also make accurate predictions about when a crime was about to occur. Accurate predictions also tended to be preceded by comments about body language and the social proximity of people in the CCTV footage.

'For certain types of crime, it may be that understanding the social context and the relations between those in the CCTV image is the first step towards obtaining reliable indicators of criminal intent,' the researchers concluded. Of course, whether we actually want CCTV operators, accurate or otherwise, watching our movements and forecasting crimes is another question altogether.
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Grant, D., & Williams, D. (2010). The importance of perceiving social contexts when predicting crime and antisocial behaviour in CCTV images. Legal and Criminological Psychology DOI: 10.1348/135532510X512665

The fingerprint of where and when a burglary is committed

In the land of fiction, it's the criminal's modus operandi - his method of entry, his taste for certain jewellery and so forth - that can be used by detectives to identify his handiwork. The reality according to a new analysis of solved burglaries in the Northamptonshire region of England is that these aspects of criminal behaviour are on their own unreliable as identifying markers, most likely because they are dictated by circumstances rather than the criminal's taste and style. However, the geographical spread and timing of a burglar's crimes are distinctive, and could help with police investigations.

Lucy Markson and colleagues analysed 160 burglaries committed in Northamptonshire between 2006 and 2008 by 80 male serial offenders. Each burglar had committed two of the crimes. Markson jumbled up the burglaries and looked to see if two crimes committed by the same offender - so-called 'linked crimes' - were more similar, on average, on a range of factors, than two crimes committed by two different offenders.

Each burglary was analysed according to its timing, geographical location, and over 79 aspects of modus operandi behaviour categorised together under three domains: 'entry behavior', 'target selection', and 'property stolen'. Comparing crimes across each of these domains one at a time failed to distinguish between linked and unlinked crimes. Only when all three domains of modus operandi behaviour were considered together were burglaries by the same man distinguished from those by two different men (but still only with an accuracy of 58 per cent).

The key finding is that even more effective as a distinguishing factor than all three domains of modus operandi behaviour combined was geographical location. That is, two burglaries within Northamptonshire committed by the same man tended to be closer together geographically than two burglaries committed by two different men. Timing was another useful factor - two crimes by the same burglar tended to happen closer together in time (measured in days) than unlinked burglaries. Combining timing and spatial distance correctly identified 86 per cent of burglary pairs as either linked or unlinked.

Another pattern the researchers looked for was whether modus operandi behaviours are more similar between two crimes occurring closer together in time, but no such pattern was observed.

Timing and spatial distance have been identified as useful markers of linked crimes before but only ever in metropolitan areas, so this is the first demonstration in a more rural, sparsely populated context. 'The current study has shown that offenders do exhibit a degree of consistency and distinctiveness across certain crime behaviours but that not all offence behaviour can be used to accurately distinguish between burglaries committed by the same and different offenders,' the researchers concluded.
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Markson, L., Woodhams, J., & Bond, J. (2010). Linking serial residential burglary: comparing the utility of modus operandi behaviours, geographical proximity, and temporal proximity. Journal of Investigative Psychology and Offender Profiling DOI: 10.1002/jip.120

What's this psychopathy hoo-ha all about?

A psychology paper, by David Cooke and Jennifer Skeem, that's critical of the dominant tool for measuring psychopathy, has finally been published after years lying dormant. The delay, according to reports, was due to threats of libel by lawyers representing Robert Hare, author of the criticised tool.

Curiously, back in 2007, when the contentious paper was first moth-balled, a similar and related paper (free to access), also by Cooke and Skeem, plus statistician Christine Michie, was published in the British Journal of Psychiatry. In fact, this paper describes itself as the 'analytical' companion to the 'logical and theoretical' paper that was buried for so long.

So what did the paper that managed to get published back in 2007 have to say? Echoing the scholarly tussles that have surrounded the measurement of many factors in psychology, such as intelligence and personality, Cooke and his co-authors grapple with how best to provide a concrete measurement of a slippery abstract concept, in this case psychopathy.

The gist of their argument is that psychopathy is most appropriately measured by a three-factor version of Hare's Psychopathy Checklist-Revised (PCL-R), tapping: arrogant and deceitful interpersonal style; deficient affective experience; and impulsive and irresponsible behavioural style. In short-hand you could say this translates as nasty, unemotional and uninhibited. The point of contention is that Hare's widely used PCL-R measure of psychopathy adds a fourth factor - criminality.

Cooke and his colleagues think this is a big mistake and to support their claims they ran a number of different versions of the psychopathy checklist on answers given by over 1000 adult male offenders. In conclusion, they wrote:

'Psychopathy and criminal behaviour are distinct constructs. If we are to understand their relationships and, critically, whether they have a functional relationship, it is essential that these constructs are measured separately. This is particularly critical within the context of the Dangerous and Severe Personality Disorders project, where individuals are detained because of the assumption of a functional link between their personality disorder and the risk that they pose.'

In other words, a measure that conflates psychopathy and criminality risks confusing any attempts to understand the links between psychopathy and criminal acts such as rape and murder. Moreover, if raping and murdering become part of the definition of psychopathy, then what sense is there of running a risk assessment on a person diagnosed as psychopathic?

Cooke et al are currently developing what they describe as a 'more comprehensive' model of the construct of psychopathy based on 33 symptoms grouped into six domains. Criminality isn't one of them.
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Cooke, D., Michie, C., & Skeem, J. (2007). Understanding the structure of the Psychopathy Checklist - Revised: An exploration of methodological confusion. The British Journal of Psychiatry, 190 (49) DOI: 10.1192/bjp.190.5.s39

Link to Mind Hacks update on the saga of the buried paper (thanks to Mind Hacks for alerting me to this unfolding story).
Link to In the News Forensic Psychology blog, with more updates.
Link to related (paywalled) Science journal news item.

Drawing out the truth

Forget expensive fMRI-based lie detection or iffy polygraph tests, give your suspect a pencil and paper and get them to draw what happened - a new study suggests their artistic efforts will betray whether they are telling the truth or not.

Aldert Vrij's new study involved 31 police and military participants going on a mock mission to pick up a package from another agent before delivering it somewhere else. Afterwards the participants answered questions about the mission. Crucially, they were also asked to draw the scene of the package pick-up. Half the participants acted as truth-tellers, the others played the part of liars.

Vrij's team reasoned that clever liars would visualise a location they'd been to, other than where the exchange took place, and draw that. They further reasoned that this would mean they'd forget to include the agent who participated in the exchange. This thinking proved shrewd: liars indeed tended not to draw the agent, whereas truth-tellers did. In fact, 80 per cent of truth tellers and 87 per cent of liars could be correctly classified on the basis of this factor alone.

'These are high accuracy rates and will be difficult to exceed by any traditional verbal, nonverbal or physiological lie detection tool,' Vrij's team said. 'In fact, we would certainly expect such tools to fare worse.'

Another distinguishing factor was the perspective of the drawing. Fifty-three per cent of truth-tellers penned a drawing from their own first-person perspective at the scene; 47 per cent opted for a birds-eye view. By contrast, 81 per cent of liars went for the birds-eye view and just 19 per cent for the first-person perspective.

The researchers said theirs was the first study of its kind and they acknowledged many questions were left unanswered. 'We believe that our findings justify taking drawing seriously as a lie detection tool, and that it will encourage researchers to carry out drawing research.'
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Vrij, A., Leal, S., Mann, S., Warmelink, L., Granhag, P., & Fisher, R. (2010). Drawings as an innovative and successful lie detection tool. Applied Cognitive Psychology DOI: 10.1002/acp.1627

Darkness encourages unethical behaviour even when it makes no difference to anonymity

Imagine a man sits alone, hunched over his desk, fingers tapping out a project progress report to his boss. Does he decide to lie? If I told you that the sun had nearly set, filling the man's room with darkness, would that make any difference to your answer? It should do. A new study suggests that darkness encourages cheating, even when it makes no difference to anonymity.

Chen-Bo Zhong and colleagues had dozens of undergrad students complete a basic maths task against a time limit. Afterwards they had to fill in an anonymous form indicating how many items out of twenty they'd answered correctly and they had to take a monetary reward from an envelope (up to twelve dollars) in line with their performance. Half the students completed the task in a dimly lit room (though still light enough to see each other) whilst the other half completed the task in a bright room.

A surreptitious coding system allowed the researchers to match up the students' self-completed scoring cards with their actual performance. You guessed it, the students in the dimly lit room tended to exaggerate their performance more than the control group in the bright room (by an average of 4.21 items vs. 0.83 items). Another way of looking at it is that 60.5 per cent of participants in the dim room exaggerated their performance compared with just 24.4 per cent of participants in the bright room.

In the same way that young kids think they are invisible when they cover their eyes, Chen-Bo Zhong's team think the effect they observed occurs as an automatic response to the cover of darkness, even when the lack of light makes no difference to anonymity.

A second study supported this interpretation, finding that student participants wearing sun-glasses chose to share money less fairly in a computer-based economic game than did students wearing normal glasses. Again, the subjective reduction in light made no difference to actual anonymity as the game was played entirely via computer with a partner who participants thought was in another room. The students who said they felt more anonymous tended to share the least money, thus suggesting that perceived anonymity was mediating the effect of darkness on behaviour.

'Darkness appears to induce a false sense of concealment, leading people to feel that their identities are hidden,' the researchers said. The next time you're deliberating over a moral issue, you might want to think about whether you've got the lights on or not!
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Zhong, C., Bohns, V., & Gino, F. (2010). Good Lamps Are the Best Police: Darkness Increases Dishonesty and Self-Interested Behavior. Psychological Science DOI: 10.1177/0956797609360754

I'm not lying: Brain stimulation boosts people's deception skills

There's been so much excitement and hyperbole surrounding the promise of brain imaging as a lie detection technique, but what about the needs of the cads, thieves and vagabonds of this world? Has contemporary cognitive neuroscience nothing to offer them? It has now. In an exciting development for fibbers everywhere, Ahmed Karim and his team have shown that the application of transcranial direct current stimulation over the anterior prefrontal cortex - the front bit of the brain - improves people's lying skills.

Twenty-two participants role-played stealing money from an office before being interrogated by a researcher acting the role of police detective. The participants were given extra incentive to deceive the 'detective' with the promise that they could keep the money if they succeeded. Crucially, the participants answered some questions with a mild electric current applied over their prefrontal cortex via scalp electrodes. The effect of this 'cathodal' stimulation, which lasted about 13 minutes, was to inhibit brain activity in the affected area, thus creating a kind of temporary, 'virtual' lesion. By contrast, they answered other questions in a 'sham' condition, involving all the same kit but with the current switched off after just thirty seconds. The interrogator and participants couldn't tell whether they were in the stimulation or sham condition.

Past brain imaging research has shown that some forms of lying are associated with increased activity in the anterior prefrontal cortex, and one prediction was that inhibiting this region would impair people's lying skills. In fact, compared with the sham condition, the stimulation improved participants' lying ability: they lied more skillfully in terms of only lying when they needed to; lied more quickly; and remained calmer whilst lying, as reflected by their sweating less.

A second study used 'anodal' stimulation, which unlike 'cathodal' stimulation, excites rather than inhibits underlying brain cells. This had no effect on the participants' lying ability. A third study showed that 'cathodal' stimulation had no effect on the famous Stroop task, which requires participants to name the ink colour that a colour word (e.g. blue) is written in. In other words, the effect of the stimulation appears to be specific to deception, not to cognitively demanding tasks in general.

So why does knocking out prefrontal cortex activity improve people's deception skills? The researchers can't be sure, but stated crudely, one possibility is that the stimulation puts the conscience to sleep, freeing the mind to lie without the usual inconvenience of moral conflict. This would appear to tally with research suggesting that psychopaths have reduced grey matter in the anterior prefrontal cortex and also with a recent study showing that people with brain damage to this region make more utilitarian moral decisions.

'If neuroscience research can demonstrate that deceptive behaviour and moral cognition are not only associated with the activation of specific brain areas, but may even be modulated by noninvasive stimulation of these areas, what implications will such findings have on our concept of personal responsibility?' the researchers asked.
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Karim, A., Schneider, M., Lotze, M., Veit, R., Sauseng, P., Braun, C., & Birbaumer, N. (2009). The Truth about Lying: Inhibition of the Anterior Prefrontal Cortex Improves Deceptive Behavior. Cerebral Cortex, 20 (1), 205-213 DOI: 10.1093/cercor/bhp090