- Email: [email protected]
The truth about lie detectors
News Insight Psychology
The truth about lie detectors THE Jeremy Kyle Show, which has been broadcast in the UK since 2005, was axed by ITV last week. It featured people with troubled relationships arguing in front of a live audience, often spiced up with the addition of a lie detector test. In an episode filmed recently, but never broadcast, a guest failed such a test designed to find out if he had cheated on his fiancée. He was later found dead. Lie detector tests aren’t exactly rare on TV. We can thank Kyle’s US predecessor Jerry Springer for cementing their popularity, and they endure on shows like Love Island, another ITV programme. But their reach goes wider. In Ukraine, evidence from lie detector tests, also known as polygraphs, is admissible in court, while in the US they are used as part of the recruitment process to government jobs. All this is rather worrying as lie detectors don’t live up to their name. They have long been discredited, while other methods of finding the truth are gaining ground. “It’s good that the show has
ended,” says George Maschke, an anti-polygraph campaigner based in the Netherlands. He says the programme contributed to the public mistakenly believing that lie detectors work or have any scientific basis. ITV didn’t respond to questions about its use of lie detectors. Polygraph machines measure a person’s pulse, blood pressure and breathing while they answer a series of control questions, like what they ate for breakfast or their age. Then the person is asked a more pertinent question, such as: “Did you cheat on your partner?” If their vital signs leap, they are judged to be lying. But this is wrong. The factors being measured are designed to tally with a person’s level of arousal, which you can think of as how alert they are. Yet being asked whether you were unfaithful is the sort of thing that could make you tense up whether you were or not. This isn’t news. In the 1980s, psychologist David Lykken wrote about the lack of evidence that polygraphs could detect lies. He found that several studies
ALAMY
Polygraph machines remain in use despite being widely discredited. There are better alternatives, says Joshua Howgego
claiming they had an accuracy of 70 per cent or more were poorly designed and showed no such thing. A 2003 report by the US National Academy of Sciences reached much the same view. Maschke knows this all too
No machine needed: How language gives liars away “I am always intrigued why lie detection methods using equipment are so popular,” says social psychologist Aldert Vrij at the University of Portsmouth, UK. “To me, lies can be detected through using proper interview styles and analysing speech.” Vrij argues that methods for detecting lies based on the specificity of responses show the best results. These techniques assume that liars inevitably include fewer details when they answer questions than people telling the truth. Interviews focus
18 | New Scientist | 25 May 2019
on gathering information, starting with open questions, then probing in more detail. For instance, you might ask a person at a border crossing about their highest qualifications – and then the name of their school headmaster. One criticism of this method is that it is often tested in engineered situations where the stakes for liars are lower than they would be in real life, meaning they might not try so hard to be convincing. But in a 2015 experiment, Thomas Ormerod at the University of Sussex and Coral Dando, now at
the University of Westminster, both in the UK, asked around 200 people to pose as passengers and lie to airport security – a far more realistic scenario. These individuals passed through border control along with real passengers. Officers were asked to use either the questioning technique or a method that looks for behavioural signs of nervousness. The questioners correctly identified 66 per cent of the lying passengers, whereas those looking for behavioural signs caught only 5 per cent.
well. In 1995, he applied to work for the FBI as an intelligence officer, but failed a polygraph and was refused. “I couldn’t understand how I had failed until I read everything on polygraphs and discovered that they are nonsense,” he says. Back in 1959, Lykken had an idea for a better method, now known as the Concealed Information Test (CIT). This tries to determine not whether a person is lying, but whether they have a memory of information being presented to them. For instance, the examiner might ask someone: “Where did the thief hide what he stole? Repeat these possibilities after me. Was it in the bathroom? In the locker? On the coatrack? On the windowsill?” The person’s skin conductance is measured during these questions. If it spikes during one of them, it suggests that they are sweating more, and that option is meaningful to them.
Working hypothesis
More Insight online
Your guide to a rapidly changing world www.newscientist.com/insight
of a detail, but whether they are deliberately covering it up. Nathalie Klein-Selle at the Hebrew University of Jerusalem in Israel has found that, although increased skin conductance does reveal the presence of that memory, heart rate and breathing only change when the person is trying to conceal it. This might sound like the polygraph, but it is more reliable because the test aims to avoid inducing stress by only presenting interviewees with plausible answers. Researchers are also exploring other outward cues that could improve the CIT, including how people’s eyes move as they look at
▲ Japanese phones Digit-diallers in Japan will be jumping for joy as the country plans 10 billion new phone numbers – that’s 80 per person, which is probably enough. ▲ Underwater rock Researchers have used an X-ray laser to create the loudest possible underwater sound, at 270 decibels. Any louder, and the water would boil.
“I read everything written about polygraphs and discovered that they are nonsense” photos of faces. Psychologist Ailsa Millen at the University of Stirling in the UK has shown that the way our eyes fixate on parts of faces differs when we recognise the face. The effect is stronger for faces we know best, such as close friends. Millen is now working on a project called ConFace to develop this test, potentially for use by UK police. But many unknowns must first be resolved, including whether the test works equally well when people from one culture look at faces from another. Millen is currently studying whether people can conceal their recognition of faces. All of which means there is little excuse for still using polygraphs, whether on TV or elsewhere. For his part, Maschke is campaigning for them to be dropped, like Kyle’s show itself. “Our focus is on public education,” he says. “For policy reform to happen, more people have to understand why lie detectors are not reliable.” ❚
▲ Minecraft In a battle of the blocks, Minecraft has become the best-selling video game of all time, beating Tetris with 176 million copies sold. ▲ ▼ Bitcoin The cryptocurrency hit a recent high of $8000, but, honestly, who knows what the price will be by the time this goes to print. ▼ Woody Harrelson New York police used face recognition on a picture of the actor to hunt down a suspect who looked vaguely like him, a move which doesn’t seem at all worrying. TOP: GETTY; BOTTOM: REX/SHUTTERSTOCK
ITV
Lie detectors (above), which track pulse, blood pressure and breathing, were often used on The Jeremy Kyle Show (below)
The test is different to the polygraph because all the options are part of the same overall question. And if a person says they have no knowledge of the crime, but the test indicates they do, you can infer they are probably lying. It has been used for years by police in Japan to help direct enquiries in the early stages of investigations. Although the CIT rests on solid foundations, it isn’t a perfect memory detector. A 2014 metaanalysis of about 100 studies of CITs did uncover a significant statistical difference between the results of people with guilty knowledge and without it. Yet, at best, a person who does have such a memory would be about 90 per cent more likely to get a higher skin conductance reading than someone who doesn’t. That might sound high, but a test with that success rate is likely to produce false negatives: results suggesting that people don’t have knowledge when they actually do. Linda Geven, a legal psychologist at the University of Amsterdam in the Netherlands says this shows why the CIT shouldn’t be relied on in court as the sole proof of guilt. “You would use it more in the investigation stage,” she says. “For example, to work out if the police should look at one suspect more closely than the others.” Even then, what CIT does detect may not always be a relevant “memory trace”, as Geven calls them. For example, interviewees might recognise a suspect from news reports, even when they don’t really know them. She is researching whether asking more specific questions could get around this. More recently, it has emerged that the CIT may reveal not just whether people have a memory
Sorting the week’s supernovae from the absolute zeros
25 May 2019 | New Scientist | 19
The truth about lie detectors THE Jeremy Kyle Show, which has been broadcast in the UK since 2005, was axed by ITV last week. It featured people with troubled relationships arguing in front of a live audience, often spiced up with the addition of a lie detector test. In an episode filmed recently, but never broadcast, a guest failed such a test designed to find out if he had cheated on his fiancée. He was later found dead. Lie detector tests aren’t exactly rare on TV. We can thank Kyle’s US predecessor Jerry Springer for cementing their popularity, and they endure on shows like Love Island, another ITV programme. But their reach goes wider. In Ukraine, evidence from lie detector tests, also known as polygraphs, is admissible in court, while in the US they are used as part of the recruitment process to government jobs. All this is rather worrying as lie detectors don’t live up to their name. They have long been discredited, while other methods of finding the truth are gaining ground. “It’s good that the show has
ended,” says George Maschke, an anti-polygraph campaigner based in the Netherlands. He says the programme contributed to the public mistakenly believing that lie detectors work or have any scientific basis. ITV didn’t respond to questions about its use of lie detectors. Polygraph machines measure a person’s pulse, blood pressure and breathing while they answer a series of control questions, like what they ate for breakfast or their age. Then the person is asked a more pertinent question, such as: “Did you cheat on your partner?” If their vital signs leap, they are judged to be lying. But this is wrong. The factors being measured are designed to tally with a person’s level of arousal, which you can think of as how alert they are. Yet being asked whether you were unfaithful is the sort of thing that could make you tense up whether you were or not. This isn’t news. In the 1980s, psychologist David Lykken wrote about the lack of evidence that polygraphs could detect lies. He found that several studies
ALAMY
Polygraph machines remain in use despite being widely discredited. There are better alternatives, says Joshua Howgego
claiming they had an accuracy of 70 per cent or more were poorly designed and showed no such thing. A 2003 report by the US National Academy of Sciences reached much the same view. Maschke knows this all too
No machine needed: How language gives liars away “I am always intrigued why lie detection methods using equipment are so popular,” says social psychologist Aldert Vrij at the University of Portsmouth, UK. “To me, lies can be detected through using proper interview styles and analysing speech.” Vrij argues that methods for detecting lies based on the specificity of responses show the best results. These techniques assume that liars inevitably include fewer details when they answer questions than people telling the truth. Interviews focus
18 | New Scientist | 25 May 2019
on gathering information, starting with open questions, then probing in more detail. For instance, you might ask a person at a border crossing about their highest qualifications – and then the name of their school headmaster. One criticism of this method is that it is often tested in engineered situations where the stakes for liars are lower than they would be in real life, meaning they might not try so hard to be convincing. But in a 2015 experiment, Thomas Ormerod at the University of Sussex and Coral Dando, now at
the University of Westminster, both in the UK, asked around 200 people to pose as passengers and lie to airport security – a far more realistic scenario. These individuals passed through border control along with real passengers. Officers were asked to use either the questioning technique or a method that looks for behavioural signs of nervousness. The questioners correctly identified 66 per cent of the lying passengers, whereas those looking for behavioural signs caught only 5 per cent.
well. In 1995, he applied to work for the FBI as an intelligence officer, but failed a polygraph and was refused. “I couldn’t understand how I had failed until I read everything on polygraphs and discovered that they are nonsense,” he says. Back in 1959, Lykken had an idea for a better method, now known as the Concealed Information Test (CIT). This tries to determine not whether a person is lying, but whether they have a memory of information being presented to them. For instance, the examiner might ask someone: “Where did the thief hide what he stole? Repeat these possibilities after me. Was it in the bathroom? In the locker? On the coatrack? On the windowsill?” The person’s skin conductance is measured during these questions. If it spikes during one of them, it suggests that they are sweating more, and that option is meaningful to them.
Working hypothesis
More Insight online
Your guide to a rapidly changing world www.newscientist.com/insight
of a detail, but whether they are deliberately covering it up. Nathalie Klein-Selle at the Hebrew University of Jerusalem in Israel has found that, although increased skin conductance does reveal the presence of that memory, heart rate and breathing only change when the person is trying to conceal it. This might sound like the polygraph, but it is more reliable because the test aims to avoid inducing stress by only presenting interviewees with plausible answers. Researchers are also exploring other outward cues that could improve the CIT, including how people’s eyes move as they look at
▲ Japanese phones Digit-diallers in Japan will be jumping for joy as the country plans 10 billion new phone numbers – that’s 80 per person, which is probably enough. ▲ Underwater rock Researchers have used an X-ray laser to create the loudest possible underwater sound, at 270 decibels. Any louder, and the water would boil.
“I read everything written about polygraphs and discovered that they are nonsense” photos of faces. Psychologist Ailsa Millen at the University of Stirling in the UK has shown that the way our eyes fixate on parts of faces differs when we recognise the face. The effect is stronger for faces we know best, such as close friends. Millen is now working on a project called ConFace to develop this test, potentially for use by UK police. But many unknowns must first be resolved, including whether the test works equally well when people from one culture look at faces from another. Millen is currently studying whether people can conceal their recognition of faces. All of which means there is little excuse for still using polygraphs, whether on TV or elsewhere. For his part, Maschke is campaigning for them to be dropped, like Kyle’s show itself. “Our focus is on public education,” he says. “For policy reform to happen, more people have to understand why lie detectors are not reliable.” ❚
▲ Minecraft In a battle of the blocks, Minecraft has become the best-selling video game of all time, beating Tetris with 176 million copies sold. ▲ ▼ Bitcoin The cryptocurrency hit a recent high of $8000, but, honestly, who knows what the price will be by the time this goes to print. ▼ Woody Harrelson New York police used face recognition on a picture of the actor to hunt down a suspect who looked vaguely like him, a move which doesn’t seem at all worrying. TOP: GETTY; BOTTOM: REX/SHUTTERSTOCK
ITV
Lie detectors (above), which track pulse, blood pressure and breathing, were often used on The Jeremy Kyle Show (below)
The test is different to the polygraph because all the options are part of the same overall question. And if a person says they have no knowledge of the crime, but the test indicates they do, you can infer they are probably lying. It has been used for years by police in Japan to help direct enquiries in the early stages of investigations. Although the CIT rests on solid foundations, it isn’t a perfect memory detector. A 2014 metaanalysis of about 100 studies of CITs did uncover a significant statistical difference between the results of people with guilty knowledge and without it. Yet, at best, a person who does have such a memory would be about 90 per cent more likely to get a higher skin conductance reading than someone who doesn’t. That might sound high, but a test with that success rate is likely to produce false negatives: results suggesting that people don’t have knowledge when they actually do. Linda Geven, a legal psychologist at the University of Amsterdam in the Netherlands says this shows why the CIT shouldn’t be relied on in court as the sole proof of guilt. “You would use it more in the investigation stage,” she says. “For example, to work out if the police should look at one suspect more closely than the others.” Even then, what CIT does detect may not always be a relevant “memory trace”, as Geven calls them. For example, interviewees might recognise a suspect from news reports, even when they don’t really know them. She is researching whether asking more specific questions could get around this. More recently, it has emerged that the CIT may reveal not just whether people have a memory
Sorting the week’s supernovae from the absolute zeros
25 May 2019 | New Scientist | 19