Category Archives: Psychophysiology

Research Round-up 5: Polygraphy

Part 5 in the rapid research round-up for 2008 includes some of the articles to appear over the last year relating to physiological detection of deception.

The first paper here is the most interesting to me, particularly because there are rather few published research findings relating to what happens when people are polygraphed in their non-native language, but the others are probably only really of interest to hard-core psychophysiologists. If these all seem pretty heavy then I’d recommend heading over to a delightful post about William Moulton Marsden, one of the early pioneers of the polygraph, written by Romeo Vitelli at the Providentia blog, for some light relief.

Bilingual speakers frequently report experiencing greater emotional resonance in their first language compared to their second. In Experiment 1, Turkish university students who had learned English as a foreign language had reduced skin conductance responses (SCRs) when listening to emotional phrases in English compared to Turkish, an effect which was most pronounced for childhood reprimands. A second type of emotional language, reading out loud true and false statements, was studied in Experiment 2… Results suggest that two factors influence the electrodermal activity elicited when bilingual speakers lie in their two languages: arousal due to emotions associated with lying, and arousal due to anxiety about managing speech production in non-native language. Anxiety and emotionality when speaking a non-naive language need to be better understood to inform practices ranging from bilingual psychotherapy to police interrogation of suspects and witnesses.

The effects of the state of guilt and the context in which critical information was received on the accuracy of the Concealed Information Test (CIT) were examined in a between-subjects mock crime experiment… Results indicated that accomplices were more effectively detected than innocent participants, although both were given the same critical information. Information gathered in the crime context yielded stronger orientation to the critical items than similar information gathered in a neutral context.

The present mock-crime study concentrated on the validity of the Guilty Actions Test (GAT) and the role of the orienting response (OR) for differential autonomic responding. N = 105 female subjects were assigned to one of three groups: a guilty group, members of which committed a mock-theft; an innocent-aware group, members of which witnessed the theft; and an innocent-unaware group… For informed participants (guilty and innocent-aware), relevant items were accompanied by larger skin conductance responses and heart rate decelerations whereas irrelevant items elicited HR accelerations. Uninformed participants showed a non-systematic response pattern.

Following the idea that response inhibition processes play a central role in concealing information, the present study investigated the influence of a Go/No-go task as an interfering mental activity, performed parallel to the Concealed Information Test (CIT), on the detectability of concealed information… No physiological evidence for an interaction between the parallel task and sub-processes of deception (e.g. inhibition) was found. Subjects’ performance in the Go/No-go parallel task did not contribute to the detection of concealed information.

The Concealed Information Test (CIT) requires the examinee to deceptively deny recognition of known stimuli and to truthfully deny recognition of unknown stimuli. Because deception and orienting are typically coupled, it is unclear how exactly these sub-processes affect the physiological responses measured in the CIT…The present study aimed at separating the effects of deception from those of orienting…The findings further support the notion that psychophysiological measures elicited by a modified CIT may reflect different mental processes involved in orienting and deception.

The final part of this research round-up includes papers on children’s deception, and on technotreachery.

Polygraph reasoning applied to spotting terrorists…

Remember that the rationale behind the polygraph is that (with an appropriate questioning regime) guilty people are assumed have physiological responses that differ from innocents? Well, the new “anxiety-detecting machines” that the DHS hopes might one day spot terrorists seem to work on the same basis. Here’s the report from USA Today (18 Sept):

A scene from the airport of the future: A man’s pulse races as he walks through a checkpoint. His quickened heart rate and heavier breathing set off an alarm. A machine senses his skin temperature jumping. Screeners move in to question him. Signs of a terrorist? Or simply a passenger nervous about a cross-country flight?

It may seem Orwellian, but on Thursday, the Homeland Security Department showed off an early version of physiological screeners that could spot terrorists. The department’s research division is years from using the machines in an airport or an office building— if they even work at all. But officials believe the idea could transform security by doing a bio scan to spot dangerous people.

Critics doubt such a system can work. The idea, they say, subjects innocent travelers to the intrusion of a medical exam.

According to the news report, there is some effort going into testing the equipment, though if the details in the news report are to be believed it sounds like the research is still at a very early stage:

To pinpoint the physiological reactions that indicate hostile intent, researchers… recruited 140 local people with newspaper and Internet ads seeking testers in a “security study.” Each person receives $150.

On Thursday, subjects walked one by one into a trailer with a makeshift checkpoint. A heat camera measured skin temperature. A motion camera watched for tiny skin movements to measure heart and breathing rates. As a screener questioned each tester, five observers in another trailer looked for sharp jumps on the computerized bands that display the person’s physiological characteristics.

Some subjects were instructed in advance to try to cause a disruption when they got past the checkpoint, and to lie about their intentions when being questioned. Those people’s physiological responses are being used to create a database of reactions that signal someone may be planning an attack. More testing is planned for the next year.

The questioning element does make it sound like what is being developed is a ‘remote’ polygraph.

Hat tip to Crim Prof Blog.

UPDATE: Lots of places picking this up all over the www. New Scientist has a post on the same topic here, and an earlier article on the system here. The Telegraph’s report adds some new information.

Deception research across the blogosphere

The physiology of lying by exaggerating: Over at the BPS Research Digest Blog, a summary of research that has caused ripples around the media: lying by exaggeration doesn’t seem to cause the typical physiological arousal effects that some associate with liars:

Telling lies about our past successes can sometimes be self-fulfilling, at least when it come to exam performance. That’s according to the New York Times, which reports on studies by Richard Gramzow at the University of Southampton and colleagues.

Their research has shown that, when asked, many students exaggerate their past exam performance, and that those students who do this tend to go on to perform better in the future.

What’s more, a study published in February showed that when these exaggerators are interviewed about their past academic performance, they don’t show any of the physiological hallmarks associated with lying, but rather their bodies stay calm. It’s almost as though this is a different kind of lying, aimed more at the self, with the hope of encouraging improved future performance.

More commentary on this research over at Deric Bownds’ Mind Blog.


Two popular articles on deception: Via the Situationist Blog (7 April), a link to an article in Forbes on “how to sniff out a liar” (which doesn’t include any hints for olfactory detection of deceivers!). And hat tip to the Antipolygraph Blog (16 April) for pointing us toThe Lie of Lie Detectors By Rob Shmerling:

Recently, two studies announced effective ways to determine whether a person was telling the truth — one used a brain scan while the other detected heat around the face. Since you probably tell the truth all of the time, it is likely that these reports will have no direct bearing on you. But, for those who perform lie detector tests or for those who might be asked to submit to one, these techniques could someday change how these tests are performed.

The Pentagon’s “Porta-Poly”: The news that the Pentagon is trialling a ‘pocket lie detector’ known as the Preliminary Credibility Assessment Screening System (PCASS) for soldiers has been picked up and commented upon by a number of sources including Bruce Schneier and the Anti-Polygraph Blog, but don’t skip the original MSN story which is well worth reading.

Update: Missed one: Over at Practical Ethics, in Fighting Absenteeism with Voice Analysis (16 May).  The news that some companies are apparently considering using this discredited technology to check up on workers calling in sick is chilling.

Polygraphing sex offenders in the UK and US$5 million for ERP research

The BBC’s online News Magazine featured an article discussing the recent US grant to Jennifer Vendamia to further her research on ERPs and deception, linking it to the recent decision to polygraph sex offenders in UK prisons.

The future of lying, BBC News, 14 January, 2005

As the British government unveils plans to make lie detector tests mandatory for convicted paedophiles, some scientists in the US are working on more advanced technology which might be better equipped at detecting deception. […] The US Department of Defense has given Dr Jennifer Vendemia a $5m grant to work on her theory that by monitoring brainwaves she can detect whether someone is lying. She claims the system has an accuracy of between 94% and 100% and is an improvement on the existing polygraph tests, which rely on heart rate and blood pressure, respiratory rate and sweatiness.

Gut reactions may rumble a liar, 31 October 2005

Liars could be caught out by the reaction of their stomachs to telling untruths, suggests preliminary research from the University of Texas, US. The team believe that the early-stage technique could one day improve the accuracy of polygraph tests, which rely mostly on monitoring heart activity. […] “This might very well be the case,” says Kevin Murphy, a psychologist at Penn State University, Pennsylvania, US, who recently headed a panel for the US National Academy of Sciences to analyse the science behind polygraph devices. “But polygraph detectors, whatever their ilk, measure stress and not lying. This new test might give more, potentially very useful, data. But it won’t give you the definitive truth.”

See also the International Herald Tribune, 9 Nov 2005: In a lie, your gut may give you away

Psychophysiological and vocal measures in the detection of guilty knowledge

Matthias Gamer, Hans-Georg Rill, Gerhard Vossel, and Heinz Werner Godert
International Journal of Psychophysiology, article in press, available online July 2005

The Guilty Knowledge Test (GKT) and its variant, the Guilty Actions Test (GAT), are both psychophysiological questioning techniques aiming to detect guilty knowledge of suspects or witnesses in criminal and forensic cases. Using a GAT, this study examined the validity of various physiological and vocal measures for the identification of guilty and innocent participants in a mock crime paradigm. Electrodermal, respiratory, and cardiovascular measures successfully differentiated between the two groups. A logistic regression model based on these variables achieved hit rates of above 90%. In contrast to these results, the vocal measures provided by the computerized voice stress analysis system TrusterPro were shown to be invalid for the detection of guilty knowledge.