A Reflection on Stephen Kosslyn’s talk “Brain Bases of Deception: Why We Probably Will Never Have a Perfect Lie Detector”
The premise of lie detection is that there is some perceivable physical sign when someone is lying. We have many beliefs about what these signs may be. For instance, we may want someone to look us in the eye when they are recounting a suspect tale, because we believe that direct eye contact is difficult for liars. We are confident of out ability to spot a lie, but in practice it is difficult: we’re not nearly as good as we think we are (indeed, some studies show that many people do not do much better than chance). Being deceived is quite harmful, so this is a big problem.
People have long sought ways to determine who is lying. In the Middle Ages, suspects were put through ordeals, such as dipping their arm in boiling waters— if they did not blister were they considered innocent. In ancient China, suspects were made to chew dry rice and spit it out; if it remained dry they were convicted.
While today we do not look for immunity from injury as a sign of innocence, modern polygraphs work on the same principle as chewing dried rice – they emphasis physical responses that are believed to insuppressibly accompany lying. The rice test sought to detect dry mouth, a sign of nervousness; today’s polygraphs often measure heart rate, respiration, and how sweaty one’s hands are (Galvantic Skin Response or GSR).
They are unreliable because they are based on side effects of the phenomenon they seek to measure. The investigator wants to know if the subject is telling a lie. However, what the polygraph measures are physiological symptoms of emotions that may accompany lying, i.e. stress, nervousness and fear. They are not measuring the lying itself—that is, the creation of a false narrative— but are instead looking at how one responds to the act of lying. They are not looking at the thought-process itself, but at the symptoms that accompany a state of aroused feeling.
When using these measurements, false positives are a clear possibility: some people respond nervously because of the situation. And there are numerous false negatives. If someone does not feel guilt or fear about lying – at the extreme, the most pathological of liars – they will appear on a polygraph test to be truthful. In addition, there are many techniques for fooling the polygraph, such as putting a nail in your shoe and pressing on it to experience pain with each answer, including ones where you are known to be telling the truth, in order to alter your response profile.
Looking at these attempts to measure physical corollaries of deception, Stephen Kosslyn and his colleagues asked: Why look at the side effects of lying? Why not go right to the source – what is the brain doing? What can we see in brain activity that enables us to distinguish lying from truth-telling?
One of the main themes running through Professor Kosslyn’s research has been the idea that the processes that we think of as a “single activity” are, when you see what the brain is doing, comprised of multiple functions. For example, we think of identifying a thing – that’s a chair, that’s a bluejay – as a singular activity. But it turns out identifying something at a general level – there’s a bird – uses a different part of the brain than identifying it at a more specific level – there’s a robin. .
Lying, too, is a complex mental process and different types of lies use different parts of the brain. For instance, Kosslyn and colleagues looked at the difference between spontaneous lies and lies that had been rehearsed, and found that the pattern of neural activity was quite different for each. Rehearsed lies, for example, elicit more activation in the right anterior frontal cortice, a part of the brain used in recalling episodic memory. And there are many other features that distinguish different types of lies. There are lies about yourself and lies about other people. There are lies that you think are justified and lies you think are wrong. All of these would not only have a different neural activation pattern than the corresponding truth, they might also all be distinct from one another. One of Kosslyn’s main conclusions is that a reliable neural imaging lie-detector is unlikely: there are too many factors that go into lying to make a recognizable signature of it feasible.
Significant individual differences further complicate the situation. Although a particular brain region may be activated inmost people when they make a certain kind of lie, that pattern is not universal. Differences may be caused by differences in how they perceived a certain kind of lie (indeed, even in neutral tasks such as bird recognition, there is significant individual differences that result from differing levels of expertise. For me, recognizing a bird as a robin is pretty specific, but for a serious bird watcher, robin is a general category). Differences may also be the result of individual variations in brain function.
Kosslyn entitled his talk “Why We Probably Will Never Have a Perfect Lie Detector.” It’s a provocative title, in light of all the research now being done on finding the neural correlates of deception.
Is our understanding of the brain simply at an early stage now, and as it advances, we will indeed be able to look into someone’s head and know if they are lying? There are people who are exceptional human lie-detectors, able to distinguish truth telling from deception at a remarkably high rate, without the benefit of technological tools What do they see in another’s demeanor that reveals the lie – and if this can be read via physical manifestations, should it not be equally if not more possible to read these results from the brain itself?
Or is the problem with the concept of “lie” itself? Our folk understanding of lies distinguishes between social lies and harmful lies. Research such as Kosslyn’s experiments further reveals the cognitive complexity behind deception.
Finally, scientists are usually confident – if not over-confident – that the problem they are pursuing with their research will be solved. But here, with the claim that “we probably never will have a perfect lie detector” are we hearing a frank assessment of the difficulties facing a research agenda — or a note of hope? Social lies aside, deception is destructive—it is the tool of criminals and cheaters. But deception is also tied to privacy. If I can lie, I am in control of the contents of my mind. It is how we keep secrets. The perfect lie detector is the end of privacy.
Judith Donath is a Berkman Faculty Fellow and was the founding director of the Sociable Media Group at the MIT Media Lab. She is leading the Berkman Center for Internet & Society’s Law Lab Spring 2010 Speaker Series: The Psychology and Economics of Trust and Honesty. Judith’s work focuses on the social side of computing, synthesizing knowledge from fields such as graphic design, urban studies and cognitive science to build innovative interfaces for online communities and virtual identities. She is known internationally for pioneering research in social visualization, interface design, and computer mediated interaction.