21 May, 2005 at 09:58 Leave a comment

It’s written all over your face

  • 12 March 2005
  • From New Scientist Print Edition. Subscribe and get 4 free issues.
  • Susan Gaidos
  • Susan Gaidos is a science writer based in Cape Elizabeth, Maine

IT IS hard not to feel a little nervous. Andrew Ryan is trained to catch liars, and I am sitting in his lab at the US Department of Defence Polygraph Institute, preparing to lay a bald-faced whopper on him.

Earlier today, I participated in a mock crime, a short-lived melee that ended in aggravated assault, attempted murder and robbery. The act of stabbing a dummy in the chest and rifling through its purse has left me feeling more than a little guilty. My accomplice has instructed me to reveal nothing. But will my discomfort give me away?

Settling into a wide, comfortable chair, I begin answering questions, while a high-resolution infrared camera scrutinises my face, watching the blood swirl just beneath the surface of my skin. The camera forms part of a prototype for a new generation of lie detectors being developed by the US government. One day, they could be used to help unmask criminals, improve screening at border crossings and checkpoints, and perhaps interrogate terrorist suspects.

The drive towards new devices comes from a desire for something a cut above the “polygraph”, the standard lie detector whose rubber tubes and wires are familiar from TV and the movies. Scientists have long attacked the device as inconclusive, and in 2002 a report commissioned by the National Research Council (NRC) in Washington DC found that the polygraph’s performance falls well short of what is needed to tell the guilty from the innocent. As a result, the US Department of Energy began scaling back the polygraph security checks it was running on its own staff.

Chew on that

All the more reason to find new ways of picking up lies, says Ryan. “We see the world as being more complex in terms of what we’re asking our agents to do. We’re not only looking for people who’ve committed a crime, we’re searching for people with intent to do harm,” he says. “The polygraph wasn’t designed to do everything. It was designed for a very specific construct.”

Lie detection has been around for centuries in various forms, based on the belief that liars and cheats betray themselves through their physiology. In ancient China suspects were given rice to chew, the idea being that liars would be too nervous to salivate so the rice would remain dry. The polygraph may be somewhat more sophisticated than the rice test, but scientists have had a field day pointing out problems with it. For starters, fear, anger and nerves all produce similar physiological responses to lying. Just taking the test can upset truthful people to the point where they appear dishonest, while practised liars can learn to outwit the machine by remaining calm.

Part of the problem is the polygraph’s intrusive nature. If I were taking a polygraph, I’d have tubes strapped around my chest and abdomen to measure my breathing rate, plus a blood-pressure cuff to record my cardiovascular activity, and electrodes attached to my fingertips to measure my perspiration. Just thinking about this is enough to make me anxious, which I can well imagine producing a false positive.

As it is, it’s just me and the camera. “The biggest advantage over what we have now is non-contact instruments. You don’t have all these things attached,” Ryan says, pointing to a couple of old polygraph tubes slung over the arm of my chair. Sure enough, coping with the cool stare of the thermal camera seems a piece of cake by contrast.

However, that camera is tracking blood flow through the smallest vessels of my face, on the lookout for minor changes. As I relax into the chair, the questioning begins. An automated voice instructs me to answer a series of questions with a simple yes or no. “Is your name Susan?” Yes. “Do you understand that I will not ask any trick questions on this test?” Yes. “Did you stab that woman downstairs this afternoon?” No.

My voice remains calm and even, and I feel no sense of flushing as I continue answering questions and read through a list of potential murder weapons, including the one I guiltily remember using earlier, a screwdriver. But as Ryan’s colleagues look through the data afterwards, they pull out two images and set them side by side. The first image looks normal. On the second, large highlighted rings of blood encircle my eyes.

If I were a real criminal, that picture could be big trouble for me. The increased blood-flow around my eyes almost certainly reveals a fight-or-flight response. And that could well mean that I lied, according to James Levine at the Mayo Clinic and Ioannis Pavlidis of the University of Houston, Texas. During an experiment one day in the late 1990s they had a thermal camera trained on a student when a heavy steel plate fell to the floor, creating a sound like a gunshot. The camera revealed blood leaving the startled student’s cheeks and rushing toward her eyes.

“We wondered whether this would be perhaps part of the flight response to drive blood flow away from unimportant areas in the head into really important areas, such as the eye region,” Levine says. They repeated the experiment with six other people, and in each case the loud noise produced an instantaneous blood surge to the eye region. The researchers dubbed this the “face of fear”, and published their findings in The Lancet in 2001.

Levine and Pavlidis next trained their camera on deception. They observed people during normal conversation and then asked them to make up stories. When challenged about their stories, the subjects showed a similar fight-or-flight response.

The pair have now teamed up with Ryan to test their device in mock crimes. In 2002, they outlined their approach in the journal Nature (vol 415, p 35) and published results in IEEE Engineering in Medicine and Biology showing that in laboratory simulations thermal facial imaging could detect deception with 84 per cent accuracy (vol 21, p 56).

What makes this method ideal for detecting deception is that unlike a pulse or respiration rate, subjects can’t manipulate their response, Levine says. “You can double your respiration rate or make it zero by holding your breath. But no one I know of knows how to change the heating of minute areas of the face by choice.”

But critics of the polygraph say they are not yet convinced this new technology will succeed where polygraphs fail. “Thermal imaging leads you to believe that it will measure deception as opposed to other physiological responses,” says Stephen Feinberg, who headed the NRC committee that reviewed scientific evidence on the polygraph. But he points out that the surge of blood occurs in lots of different measurements. “Why is that unique to deception and not other responses to questioning?”

Looking at the thermal image, I do wonder how Ryan can be sure whether the increased blood flow was prompted by a lie, or by something else. And fortunately for me, Ryan doesn’t know because he hasn’t had enough time today to work out my baseline response – how easily I startle normally. In short, he has too little evidence to expose me as a liar. I heave a sigh of relief.

But perhaps another test will help him. Ryan places me in front of a computer screen embedded with light sensors that track my eyes as I look at pictures on the screen. The idea is to watch for irregular eye movements as I view a series of images. When you view the world, your eyes move from point to point, pausing briefly to lock the high-acuity portion of your retina onto the object you are observing. Six years ago, Neal Cohen at the University of Illinois found that by tracking where you look, the number of places you look at and how long you view each area, he could tell whether you’ve seen a face or scene before.

Cohen found that people move their eyes over fewer areas when viewing familiar scenes, and gravitate to any areas of previously viewed scenes that have been modified. The following year, he showed that the same was true even in people with amnesia. The studies were published in the Journal of Experimental Psychology and Psychological Science. “We think these responses are automatic and obligatory,” he says. “And it happens very early. We think it might, in fact, happen before you’re even aware of it.”

This means even practised liars will find it tough to beat the eye-tracker. It is easy to see when people don’t follow the instructions, Cohen warns. “If you’re not looking at the image or you’re blinking, we’ll know. If you stay fixated on one point and don’t move your eyes, we’ll know. Or, if you look too little at a particular region, we will know, because that’s exactly what we’re measuring.”

Cohen’s words echo in my mind as I pore over the faces appearing one by one on the screen: a parade of smiling celebrities, earnest politicians and total strangers. My eyes freeze when the face of a recent acquaintance flashes onto the screen. It’s Curt, the kind-looking man who earlier showed me how to jab my victim with a single thrust of a Phillips screwdriver. Realising my lapse could betray me, I scan madly across the screen, moving from point to point, focusing on nothing in particular. With Ryan and his team viewing the world through my eyes, no place seems safe. Flustered, I try to will my eyes to a state of casual observation. Five long seconds pass, and I heave a sigh of relief when the image changes and Britney Spears beams out from the screen.

Guilty, or not guilty?

Cohen says the eye-tracker offers a powerful supplementary tool for detecting deception because it taps into cognitive processing, rather than guilt or emotion. “We can explore your memory for which people fit a scene, whether it’s a crime scene or any other.” So am I guilty? Once again, time constraints mean Ryan can’t fully explore my responses. “We would need further tests,” he says.

Perhaps that best summarises where the technology is at the moment. Ryan is the first to admit its shortcomings, and he plans later this year to test the eye-tracker and thermal camera in tandem, to see if using both at once can produce more conclusive results. Ryan also plans studies to see if gender, ageing, drugs or cultural differences affect the way people respond. “Part of the development of any instrument is to know its limits. As we test and go into field studies we’ll discover the weaknesses, and find where these instruments work and where they don’t work,” he says.

Critics, however, are already warning that these studies will have their limits. No lie detector has yet proved itself truly reliable in real-life questioning, again because it is so hard to establish a subject’s baseline response. Aldert Vrij, a researcher on lying at the University of Portsmouth in the UK, says while mock crimes can provide some insights into lying, they can never fully simulate a high-stakes crime or conspiracy situation, where people may face severe punishment if they are caught lying. “You need some real-life data. You need to see whether you can generalise those findings to the real-live world,” Vrij says. Ryan says he will use real field agents to create more realistic mock interrogations.

If there is one technology that researchers agree could be a reliable lie detector, it is functional magnetic resonance imaging. An fMRI study last November showed that people use different parts of the brain when they lie than they do when telling the truth. The scans also showed activity in more areas of the brain when people were being deceptive. Even sceptics like Feinberg say this is the most promising technique. “On our committee there were people who thought if you’re going to find deception, you certainly would hope to find it in the brain,” he says. So did they? “If what we know from other fMRI studies is correct, there are individual differences. And if you can’t calibrate against them, this is not going to be useful for this purpose.”

Maybe I was just lucky this time. But I cannot help wondering wonder if deception is even a coherent, identifiable phenomenon. Can one set of traits or behaviours sum up all lies: the white lies we tell to prevent embarrassment, the half-truths we use to protect ourselves and the blatant falsehoods of a hardened criminal?

I ask Levine what he thinks the “face of fear” really means. “In a way, it would be fair to say we’ve discovered a concept or phenomenon that almost raises more questions than answers. But that doesn’t negate the presence of the phenomenon,” he says. Maybe researchers are onto something. But I’m glad I’m not being tried on this evidence just yet.

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