Now, she has been nominated for the title New Scientist Science Talent 2018. In an effort to drum up votes, she appeared at the ‘free market’ (vrijmarkt) in Utrecht on King’s Day with a large sign saying: ‘Ask me anything you want to know about lying’. “People often want to state their opinion about lying politicians and always seem to know how to recognise if their partner is cheating on them.”

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What do you tell people who want to know whether their partner is cheating?

“My initial answer is always: maybe you should talk to your partner first. Because lie detection does not strike me as a suitable solution. In any case, I would never apply it in my personal life.

“If you still want to use lie detection, then there are several things you can do. The first step is collecting evidence. Statements can usually be checked. You also have to ask the right questions. For example, ask for verifiable details. Someone who is lying will provide you with less details or will tell you all kinds of irrelevant details.

“You can also ask the person to tell their story backwards. This is because we think and fabricate stories in chronological order. If you actually experience something, it is present as fragments in your mind, and you can easily trace the steps backwards. But someone who is making up a story will find it much harder to tell it in a different order.”

What kind of non-verbal behaviour should you look out for?

“Liars are very conscious of how they are behaving. Some of them become nervous and that is visible in their non-verbal behaviour, but this is not the case for everyone. For people in the dark triad, lying is often enjoyable. These are people with psychopathic tendencies, Machiavellians (people who tend to use others opportunistically), or narcissists – I never make myself popular whenever I mention in lectures that economics students score higher here than other students. My research has shown that people move their entire body more when they are lying. Liars also mirror the person they are talking to more.”

Can you learn to detect deceitful behaviour?

“People are quite bad at lie detection. The more experience you have, the more self-confidence you get and the greater your tendency is to believe that you are good at it. But that is unjustified: people barely improve at detecting lies through knowledge and experience. It is actually impossible to learn. Though I should mention that nearly all lie detection research is experimental research. There is not much at stake. Field research is difficult, since in the real world you rarely discover what we call the ground truth; what actually happened. And if you cannot be certain whether someone is lying or not, then you cannot draw conclusions about deceitful behaviour.

Why did you decide to do research using motion capture suits?

“The scientific debate about lie detection using non-verbal behaviour was somewhat stuck in a rut. A great deal of the same kind of research was being done, from which all kinds of different conclusions were being drawn. But I realised that the methods being used for all this research were too limited. You have someone tell the truth and tell a lie, film it, and watch it while manually noting what you think is deceitful behaviour. That is rather biased, extremely time-consuming and also binary: looking away or not, moving the right hand or not when lying. While non-verbal behaviour is actually much more complex. Motion capture is much better at recording the complexity of human movement.”

This video gives an explanation of how lie detection using motion capture suits works.

Have you ever tested motion capture equipment in practice?

“Yes, extensively. I worked with colleagues and the BBC to make a Horizon documentary: A week of living truthfully. For this documentary, we tested the effectiveness of various lie detection methods in the real world and it went rather well. The documentary will be aired this autumn, but unfortunately, I can’t give you any more information about it until then. It has certainly inspired me to carry out more tests in practice.”

Can you imagine this method also being used in a penal system?

“For a long time, lie researchers have been searching for a kind of holy grail; the human equivalent of Pinocchio’s nose. When fMRI was discovered, there was hope that lies would be detectable in the brain, but there is no such thing as a lying region of the brain. At this point, it looks like it is not possible to determine whether someone is lying with 100 percent certainty. Using a combination of techniques, you can recognise approximately 70 to 80 percent of lies. That is a lot better than the 54 percent that people are able to recognise, but still not watertight. There is also a lot of variation in deceitful behaviour. My research has shown that four in five people move more when they are lying, but one in five actually moves less. So, I do not think it would be wise to accept lie detection in Dutch courts presently.

Why is it accepted in the United States?

“The American government is indeed the largest buyer of lie detectors. Perhaps we are too sceptical of them in the Netherlands. If you use them well, it can be really useful. If you are stuck and cannot find any more evidence, lie detection could help. Compare it to eye witness statements. We accept these in court, even though research has shown that a vast number of judicial errors are caused by erroneous eye witness statements.”

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Sophie van der Zee Image credit: Rafaël Philippen

Sophie van der Zee studied Psychology in Utrecht and Maastricht and got her PhD at Lancaster University for research into lie detection using motion capture. She went on to work at King’s College in Cambridge, at TNO and at the VU in Amsterdam. Since January, she has been a university lecturer at the Erasmus School of Economics.

Van der Zee is on the shortlist of nominees for New Scientist Science Talent 2018. The five scientists with the most votes will give a presentation about their research in TivoliVredenburg in Utrecht on 31 May. A winner will also be announced on the same evening. You can Votefor Van der Zee until Sunday 6 May.

What other applications are there?

“You could use lie detection for border controls to see if a person is behaving suspiciously, for example. For this application, we have recently carried out research to try and recognise deceitful behaviour at a distance, because you cannot get everyone to wear a motion capture suit. It can be done with Kinect cameras (gaming cameras from Microsoft that are able to recognise gestures, speech and faces) or with radar, with which you can see movement under a large skirt, for example.

“You could also use it to learn more about the state of mind of an interviewee, in a job interview or a therapy session. And it is used in rehabilitation and sports research, to find the ideal golf swing, for example.”

Lie detection at a distance. That’s quite scary.

“There is a major ethical issue here. Especially if you use technology and algorithms. How can an algorithm decide that I’m lying? Why is a camera allowed to determine whether I get stopped at Schiphol Airport? That is obviously kind of a black box. Should you wish to use this kind of technology, then it would have to be done as transparently as possible. But it would have to be sufficiently vague, because if people knew how it worked, then it could be manipulated.

“And in the case of Kinect cameras and smart watches, there is also the risk of hacking. Then you are treading ground that is very interesting for intelligence services, but rather terrifying for the rest of society. It is a complex issue, for which I do not have an answer yet.”

Are intelligence services interested in your research?

“They are definitely interested. That is normal in this discipline. I talk to all kinds of interested parties, both public and private. It is good that there is interest, otherwise intelligence services would end up trailing too far behind in this field. But it is important to realise how complex lie detection is, and to conduct a political and societal debate about what is and is not acceptable.

What is your role here?

“I am not responsible for steering people in one direction or the other. My primary task is to inform them. And I also consider it my task to make this kind of research applicable in practice.”

Where does your fascination with truth and lying come from?

“My true fascination is in the broader field of legal psychology. I found my psychology studies quite interesting, but I could not quite visualise how I would apply them in the real world. Until I followed an evening course in legal psychology at Studium Generale. After the first lecture, I was hooked. It was about the reliability of eye witnesses, how to put together an identity parade, and interview techniques. In particular, it concerned all the errors that are made due to lack of knowledge about communication or building trust.”

Have you become more manipulative after years of lie research?

“I am quite a good liar, but that is not really an admirable characteristic. Due to my research, I have become much more aware of the little white lies in daily life. You know what I mean: you arrive late, because you left home too late. Then you make up an excuse. I got lost. I had to finish up something. The bridge was open. I don’t do that anymore. Now I just say: sorry, I’m late. A lot of the lies we tell are so pointless.”

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