Speaker 1: Can you get convicted in a court of law based
Speaker 1: on your brain activity? Our brain scan lie detectors going
Speaker 1: to be accepted? And when does measuring somebody's brain count
Speaker 1: as illegal search and seizure? When does it violate the
Speaker 1: privacy of the mind? What constitutional issues are triggered by
Speaker 1: all this? And what does this have to do with
Speaker 1: whether your mouth gets dry when you lie, or the
Speaker 1: orbits under your eyes get hot, or your voice constricts,
Speaker 1: and what the networks in your brain are up to
Speaker 1: when you deceive. Welcome to Inner Cosmos with me David Eagleman.
Speaker 1: I'm a neuroscientist and author at Stanford and in these
Speaker 1: episodes we sail deeply into our three pound universe to
Speaker 1: understand why and how our lives look the way they do.
Speaker 1: Today's episode is about the fascinating topic of whether we
Speaker 1: can use technology to figure out whether a person is lying.
Speaker 1: What is lie detection actually measuring? How good is it?
Speaker 1: When is it accepted in courts of law? And as
Speaker 1: we come to have better and better brain reading technology,
Speaker 1: what is the future of lie detection? So in a
Speaker 1: court of law, someone says I didn't do it. I
Speaker 1: wasn't even there that night, I was in my apartment
Speaker 1: watching TV. If there's no other information that can be gathered,
Speaker 1: like his cell phone is off, so there's no GPS
Speaker 1: signal and there's no eyewitnesses, there's no alimis. If there's
Speaker 1: no other information besides his testimony, how do you know
Speaker 1: if that's really what happened or not? Is he telling
Speaker 1: the truth or is he lying? Now? On every crime
Speaker 1: television show, there are lots of clever clues that are
Speaker 1: surfaced by the industrious detective. But the issue in real
Speaker 1: courts of law most of the time is that other
Speaker 1: data just isn't available, so you only have the testimony
Speaker 1: of the people who were involved. Most crime doesn't happen
Speaker 1: in fancy office buildings with full video coverage, but instead,
Speaker 1: more commonly happens in areas without any coverage, and so
Speaker 1: you need to ask people probing questions about whether they
Speaker 1: were involved and what happened, and given human nature, you
Speaker 1: really want to know whether they are telling the truth
Speaker 1: or not. So let's start today's episode with two legal cases.
Speaker 1: One involves a woman named Aditi Sharma. She moved to
Speaker 1: a town in India with her boyfriend Udit. This was
Speaker 1: an arranged marriage they were going to be together forever.
Speaker 1: But while she was there, she met a new man
Speaker 1: named Provene, and they fell in love with each other
Speaker 1: and decided that they wanted to be together rather than
Speaker 1: her and Udit being together. So she ran away with Provene,
Speaker 1: but Udit kept following them, so she and Pravene decided
Speaker 1: that they would murder Udit, and they did so by
Speaker 1: inviting him to meet them Adam McDonald's, and they gave
Speaker 1: him a popular drink in India that was laced with
Speaker 1: arsenic and he drank it and died. So she was
Speaker 1: brought up on charges of murder, and in court she
Speaker 1: denied the crime. But part of what led her murder
Speaker 1: conviction was a lie detection test what's called an electro
Speaker 1: encephalogram or EEG. So we'll come back to this in
Speaker 1: a few moments now. Case number two is in the
Speaker 1: United States, a case in Tennessee. A man named Semrau
Speaker 1: was the CEO of two nursing home facilities, and these
Speaker 1: facilities were accused of having the employees fraudulently fill out
Speaker 1: Medicare and Medicaid forms, and Semrau said, I had no
Speaker 1: knowledge of this. I did not know this was happening
Speaker 1: in my facilities. And so in going to court, he
Speaker 1: enlisted the help of a lie detection company that used
Speaker 1: new brain scan lie detection. This is a new technology
Speaker 1: that we'll talk about today. So this company did the
Speaker 1: brain scan and the results suggested that in fact Semrau
Speaker 1: was not lying, that he had no knowledge of the fraud.
Speaker 1: And so he went to court and the question is
Speaker 1: did the court accept the brain scan? The answer is
Speaker 1: they did not. They wouldn't accept in court. They said,
Speaker 1: you can't present that here. So should they have accepted it?
Speaker 1: How do we decide when to accept a new technology
Speaker 1: or not? Under what circumstances do you say this technology
Speaker 1: is good enough that it's telling us what we need
Speaker 1: to know. So these are all the issues that we're
Speaker 1: going to talk about today, and we'll get into the
Speaker 1: background of what a lie is and how you could
Speaker 1: measure something about it and where this is all going.
Speaker 1: So we'll start with the basic question of what is
Speaker 1: a lie. Well, first, lying might seem like a human invention.
Speaker 1: So it's interesting to know that we see deception throughout
Speaker 1: the kingdom of life. For example, in the world of plants,
Speaker 1: there's a type of orchid that develops to look just
Speaker 1: like a female bee, and this way male bees come
Speaker 1: and land on it, and then the plant eats them.
Speaker 1: It's a strategy of deception to lure in the bee,
Speaker 1: and we see this throughout the animal kingdom. For example,
Speaker 1: fireflies blink to say, hey, I'm here, please meet with me.
Speaker 1: And there's a predatory firefly beetle named Fotaurus, and this
Speaker 1: meetle has evolved bioluminescence so that it flashes light signals
Speaker 1: of other firefly species, and that attracts the males and
Speaker 1: then they kill and eat the males. So this is
Speaker 1: known as aggressive mimicry. They're pretending they're the other fireflies.
Speaker 1: So one way we can think about this is that
Speaker 1: they are lying. They're not displaying truthy signals about who
Speaker 1: they are, but instead they are deceiving to accomplish their ends.
Speaker 1: So deception is not simply a human thing. But let's
Speaker 1: turn to humans because that's what we care about. So
Speaker 1: the first question is how do we define a lie? Well,
Speaker 1: it turns out that's not so easy. Let's consider an
Speaker 1: example like the scientist Copernicus. He developed a mathematical model
Speaker 1: in which the sun goes around the earth, and that
Speaker 1: turns out to be totally wrong. But he wasn't lying,
Speaker 1: he wasn't intending to deceive. And occasionally what you'll find
Speaker 1: is a situation where someone tells a man this truth,
Speaker 1: but they had no intention to deceive. I'll give you
Speaker 1: an example. Some years ago, there was a Harvard kid
Speaker 1: who went out and drank too much, and as he
Speaker 1: was stumbling home, he was jumped by two locals who
Speaker 1: beat him up badly and smashed his head into the sidewalk.
Speaker 1: So in an effort to save himself, he pulled a
Speaker 1: pen knife out of his pocket and he stabbed at
Speaker 1: the assailants to get them away. So they ran away
Speaker 1: seemingly unharmed. But it turns out his knife had gone
Speaker 1: through the chest of one assailant and tore the lining
Speaker 1: around the heart, causing what's called a cardiac tamponaud in
Speaker 1: which blood fills the lining around the heart and squishes it,
Speaker 1: and within hours this assailant died. Now, when the police
Speaker 1: came to question this Harvard kid, he told them a
Speaker 1: totally untrue story about what had happened. Why, While a
Speaker 1: neurologist and researcher named Jeremy Schmahman was called in to
Speaker 1: diagnose and testify, and he realized it was because this
Speaker 1: young man had been badly concussed, His head had been
Speaker 1: pounded into the sidewalk, and his brain had constructed a
Speaker 1: false memory about the whole event. So the opposing lawyer asked,
Speaker 1: do concussions make you lie? But Schmaman explained that a
Speaker 1: patient with a concussion is not lying, he's confabulating. There's
Speaker 1: a critical difference there because the patient believes it. In
Speaker 1: other words, just because a statement is not factual doesn't
Speaker 1: make it a lie. And in a future episode, I'm
Speaker 1: going to dive really deeply into this issue about confabulation
Speaker 1: because we see this all the time in many different
Speaker 1: types of brain damage. This even happened to a Supreme
Speaker 1: Court Justice, William Douglas, who ended up with a disorder
Speaker 1: called a nosygnosia in which he lost the ability to
Speaker 1: control part of his body, and yet he spoke falsely
Speaker 1: about it. The key is he was lying, he was confabulating.
Speaker 1: He believed that he could still move his body. So
Speaker 1: there are many situations where a person can believe something
Speaker 1: falsely and that is not equivalent to a lie. And
Speaker 1: of course, this comes up all the time when people
Speaker 1: are asked about their memory of an event, because memory
Speaker 1: doesn't store sequences of zeros and ones like a computer does.
Speaker 1: And I talked about this at length in the context
Speaker 1: of eyewitness testimony in episode twenty seven. We are not
Speaker 1: like a video recorder, and my memory of something that
Speaker 1: went down might genuinely be very different from your memory.
Speaker 1: But again, if we both probe our memories in the
Speaker 1: court of law, and we have different versions, it doesn't
Speaker 1: require that one of us is purposefully lying. But let's
Speaker 1: turn to actual deceptive lies, where you're intending to fool somebody.
Speaker 1: What do we know about that? Welltive lying starts in
Speaker 1: children at about the age of five, they start to lie.
Speaker 1: It's a cognitive development. When you're very young, you believe
Speaker 1: that your parents know everything. But around five years into
Speaker 1: the game, you realize that your parents are not omniscient,
Speaker 1: they don't know everything that happened, and it strikes you
Speaker 1: that you can inject false information. And so we train
Speaker 1: our youth on the value of truth telling because this
Speaker 1: is very pro social behavior. But the fact is, when
Speaker 1: the stakes are high, humans will often continue to practice deception,
Speaker 1: perhaps in small ways throughout their lives. Now, interestingly, we
Speaker 1: see that other primates do the same thing. They do
Speaker 1: what's called tactical deception. And the general story we find
Speaker 1: across primate species is that the bigger the brain they have,
Speaker 1: the more deception they do, because bigger brains allow us
Speaker 1: to model what other brains are thinking, which allows us
Speaker 1: to be better at manipulating them. But what's interesting is
Speaker 1: that understanding what other brains are thinking is also the
Speaker 1: development that allows species to build larger social groups with
Speaker 1: richer collaborations. So we find this strange truth that the
Speaker 1: same evolution that allows us to live in groups harmoniously
Speaker 1: also allows us to deceive. Okay, so you might think, well,
Speaker 1: we have these big brains and we're able to lie.
Speaker 1: But you might think, how could you possibly build a
Speaker 1: technology that can tell whether something is a truth or untruth.
Speaker 1: It all comes down to a simple principle. Lying is hard.
Speaker 1: Why because you have to think of the true testimony
Speaker 1: and inhibit that so you don't blurt it out, and
Speaker 1: then you have to generate a plausible alternative, and all
Speaker 1: the while you have to do a good job of
Speaker 1: hiding your anxiety and guilt. You have to manage your emotions.
Speaker 1: You have to inhibit any behaviors that would give you away.
Speaker 1: You might try to generate honest looking behaviors. So that's
Speaker 1: what we're going to talk about today. How do you
Speaker 1: build a technology to detect all of that extra work
Speaker 1: that goes into a lie. Now, what you might find
Speaker 1: unexpected is that the idea of lie detection of using
Speaker 1: a technology in the courtroom, this has a long history.
Speaker 1: So take a guess when the first lie detector was
Speaker 1: used in courts two thousand years ago in China, and
Speaker 1: the technology was uncooked rice. The defendant would put uncooked
Speaker 1: rice in his mouth and he was then asked questions. Now,
Speaker 1: presumably his answers were marginally more difficult to understand, but
Speaker 1: that wasn't the important part. The critical test was whether
Speaker 1: he could spit the rice back out of his mouth.
Speaker 1: If he couldn't, it was assumed that his dry mouth
Speaker 1: served as a physiologic marker of his nervousness about lying,
Speaker 1: And the idea was that if they were telling the truth,
Speaker 1: they'd have plenty of saliva in their mouth and they'd
Speaker 1: be able to spit the rice out. So this was
Speaker 1: the first lie detector test. But Eventually, starting about a
Speaker 1: century ago, humans leveled this up. They invented what's commonly
Speaker 1: known as the polygraph test, which is usually what people
Speaker 1: refer to when they talk about a lie detector. Now,
Speaker 1: what you do is you attach some sensors to a
Speaker 1: person's hand, and you're measuring their physiologic responses while they're
Speaker 1: answering questions. You're measuring their heart rate, their blood pressure,
Speaker 1: their breathing, their skin conductance. And the underlying principle is
Speaker 1: that when a person lives, their body reveals changes because
Speaker 1: of the stress and anxiety associated with deception, and so
Speaker 1: the examiner analyzes the recordings to look for patterns or
Speaker 1: deviations that indicate lying. So to make this clear, let's
Speaker 1: zoom in on the issue of skin conductance. So you've
Speaker 1: got all these little sweat glands in your skin, and
Speaker 1: when you have a sudden stress response, those sweat glands
Speaker 1: open more, which would cause you to sweat more. But
Speaker 1: it's not sweat that's being measured here. What's being measured
Speaker 1: is that there's a slight electrical current between point A
Speaker 1: and point B across your skin, and the conductance between
Speaker 1: A and B changes when those sweat glands open, so
Speaker 1: the electrical conductance across your skin, or inversely the resistance
Speaker 1: that changes. And so the measure here is just looking
Speaker 1: at how well electricity can pass from here to there
Speaker 1: across your skin. And when you are stressed, the electricity
Speaker 1: passes better. So you get a blip on the graph
Speaker 1: when you have a sudden moment of stress. Now here's
Speaker 1: the critical point. It's not measuring a lie, it's just
Speaker 1: measuring the stress response that's associated with lying. You're looking
Speaker 1: for that stress response as a correlate of deception. So
Speaker 1: you ask me, were you at this location on the
Speaker 1: night of March first, and I say no, I wasn't.
Speaker 1: Now if I actually was there, the lie is stressful,
Speaker 1: even at a subconscious level, and that can be read
Speaker 1: out because I have an automatic under the hood stress
Speaker 1: response that registers. The sweat glands on my skin open slightly,
Speaker 1: which changes the electrical conductance across my skin, Maybe my
Speaker 1: breathing changes a bit, my heart rate changes slightly, and
Speaker 1: as a result, this deception is brought to light. Now,
Speaker 1: this is the common way to use the polygraph test,
Speaker 1: but there's also second way that it's used, and that's
Speaker 1: known as the guilty knowledge technique. It turns out that
Speaker 1: if I show you something that's familiar to you versus unfamiliar,
Speaker 1: your brain will have a different unconscious response. So imagine
Speaker 1: I show you something like a strange little three D
Speaker 1: statue of a Pokemon. So if it's the first time
Speaker 1: you've ever seen that statue, your brain has a different
Speaker 1: response to it than if it's something you've seen before.
Speaker 1: So the police or the private investigator can leverage the
Speaker 1: guilty knowledge technique because let's say they know that this
Speaker 1: unique little statue of the Pokemon was at the scene
Speaker 1: of the crime. It was on the desk of the
Speaker 1: man who got murdered. So they sit you down in
Speaker 1: the chair and they put the polygraph electrodes on your skin,
Speaker 1: and then they show you a can of coke, and
Speaker 1: then they show you a computer printer, and then they
Speaker 1: show you a large spoon, and then they show you
Speaker 1: the Pokemon statue. Woh big response. Your brain has a
Speaker 1: different response because you were there, and only somebody who
Speaker 1: had seen that statue before and therefore would have been
Speaker 1: at the scene of the crime, would have that physiologic response.
Speaker 1: You're looking for a familiarity response for something that only
Speaker 1: a person who was there would know. That's the guilty
Speaker 1: knowledge technique. It's also known as the concealed information test.
Speaker 1: And keep in mind that your brain picks up all
Speaker 1: kinds of things that you're not even aware of. So
Speaker 1: it turns out that these familiarity responses can be big,
Speaker 1: whether or not you know that you have seen that
Speaker 1: thing before. So the polygraph test is used in both
Speaker 1: these ways, judging stress or judging familiarity. So let's go
Speaker 1: back to nineteen thirty two when a couple got married
Speaker 1: in the Northwestern Crime Scene Laboratory under the polygraph test.
Speaker 1: This couple got married and the newspapers at the time
Speaker 1: reported that her heart almost stopped beating when she said
Speaker 1: I do, and he twitched a little when he said
Speaker 1: I do. And the papers reported that they thought this
Speaker 1: all looked fine and good, but of course people didn't
Speaker 1: typically get married while hooked up to this test. This
Speaker 1: was a publicity stunt because the groom was one of
Speaker 1: the founders of the polygraph test, and he had launched
Speaker 1: a polygraph testing company and he was jazzed to get
Speaker 1: this pr But let's dive into its usage. So it
Speaker 1: was first used in a criminal case in nineteen twenty
Speaker 1: three in Berkeley, California, after a retired police chief was murdered,
Speaker 1: and then it started gaining traction in law enforcement all
Speaker 1: through the twenties and thirties, and then by the time
Speaker 1: of the Cold War, there was a lot of concern
Speaker 1: about possible espionage, so a lot of agencies started to
Speaker 1: use the polygraph test for security screenings, and by the
Speaker 1: nineteen sixties, essentially all federal law enforcement agencies were leveraging
Speaker 1: this test. But then by the nineteen seventies some academics
Speaker 1: started raising questions about the accuracy of the polygraph test,
Speaker 1: because it's quite good, but it's not perfect, and so
Speaker 1: battles over its admissibility, and courts have raged since at
Speaker 1: least that time. So I'll give you a sense of
Speaker 1: how these battles can go. In nineteen ninety two, there
Speaker 1: was a US Air Force man named Edward Scheffer who
Speaker 1: applied to work at the Office of Special Investigations, and
Speaker 1: they said, cool, but you have to take a urinalysis
Speaker 1: and a polygraph test to make sure you're not on drugs.
Speaker 1: So he said, great, and he did that. What happened
Speaker 1: is that the uranalysis test came back positive for methamphetamine use.
Speaker 1: But his polygraph test in which he said I have
Speaker 1: not done any drugs since I joined the Air Force,
Speaker 1: that came back and showed no evidence of deception, in
Speaker 1: other words, showing he was not lying. Now, based just
Speaker 1: on the uranalysis, he was tried by Marshal for using
Speaker 1: drugs and at the court martial he said, yeah, I know,
Speaker 1: my year analysis came back positive, but I would like
Speaker 1: to submit my polygraph test as part of my defense
Speaker 1: because that indicates I am not lying. And the court
Speaker 1: martial judge said sorry, but as a rule, the Air
Speaker 1: Force never accepts polygraph tests in the courtroom. And Scheffer said,
Speaker 1: this violates my sixth Amendment rights, which say that I
Speaker 1: should be able to submit evidence in my defense, and
Speaker 1: you're not letting me do this. But the military court
Speaker 1: wouldn't accept the polygraph and so Scheffer was convicted and
Speaker 1: dishonorably discharged. And so he went to the Air Force
Speaker 1: Court of Appeals and they said, yeah, no, we don't
Speaker 1: have to take the polygraph test, even if it would
Speaker 1: exculpate you. So then he went to the Armed Forces
Speaker 1: Court of Appeals and they said, you know you're right,
Speaker 1: this does seem to violate your sixth Amendment right to
Speaker 1: present a defense. So this went all the way up
Speaker 1: to the Supreme Court, and they had to struggle with
Speaker 1: this because the polygraph test is controversial in many ways,
Speaker 1: and so what they decided is that they were going
Speaker 1: to side with the military on this. The military courts,
Speaker 1: they said, do not have to take polygraph evidence if
Speaker 1: they don't want to. They said, we need to preserve
Speaker 1: the jury's core function of making credibility determinations in criminal trials.
Speaker 1: In other words, they were saying, it should be about
Speaker 1: the person in the jury box making a decision, not
Speaker 1: about some machine or technology that says this is the truth.
Speaker 1: Now did their decision have something to do with the
Speaker 1: accuracy of the polygraph? Maybe? It turns out the polygraph
Speaker 1: test is actually quite good. In tests by the American
Speaker 1: Polygraph Association, they find it's about eighty seven percent accurate
Speaker 1: in determining whether someone is telling the truth or telling
Speaker 1: a although some scientists claim it's lower, maybe as low
Speaker 1: as seventy five percent. The thing to note is that's
Speaker 1: not bad, but some critics argue that you just can't
Speaker 1: accept and errorrate that high if somebody is guilt or
Speaker 1: innocence depends on this, and some courts argue that it's
Speaker 1: not just a matter of whether the accuracy is good enough.
Speaker 1: Part of the concern expressed by courts is whether jurors
Speaker 1: understand probabilities well enough. In other words, if a defendant
Speaker 1: fails the lie detector test, will a juror think, Okay, well,
Speaker 1: it's not one hundred percent accuracy. There's still a thirteen
Speaker 1: to twenty five percent chance that the machine got it wrong,
Speaker 1: and so here's how I'm going to work those probabilities
Speaker 1: into my decision. Many courts assumed, probably correctly, that the
Speaker 1: technology will sway people more than it should. They will
Speaker 1: believe whatever the machine says. And beyond the issue of
Speaker 1: jury interpretation, there's another problem as well, which is that
Speaker 1: some people are pathological liars. Some people, for example, those
Speaker 1: with psychopathy, have real deficits in empathy, and they're not
Speaker 1: good predictors of future punishment, and they lack what we
Speaker 1: might poetically call a conscience, and so for them, lying
Speaker 1: just doesn't trigger a stress response. Many of the studies
Speaker 1: on lie detection are done with undergraduates or otherwise normal people,
Speaker 1: but the people we really care about most are psychopaths,
Speaker 1: and the technology doesn't always work so well with them.
Speaker 1: So as it stands now, the polygraph test is generally
Speaker 1: not used at the federal level in the United States
Speaker 1: unless the prosecution and defense both agree to allow it,
Speaker 1: and at the state level it varies widely. Essentially one
Speaker 1: half of the states allow polygraph results while the other
Speaker 1: half generally prohibits them. But the polygraph test, which has
Speaker 1: been around for over a century now, is just one
Speaker 1: method that people use, and as science cranks forward, there
Speaker 1: have been many newer proposals. Actually a lot of these
Speaker 1: ideas sprung up after nine to eleven when people wondered
Speaker 1: how can you do lie detection on big groups of
Speaker 1: people quickly. So one of these techniques is thermal imaging.
Speaker 1: There's some evidence that when you're lying, you get hotter
Speaker 1: under the orbits of your eyes. So the idea is
Speaker 1: to use cameras at airports to do infrared imaging as
Speaker 1: people are passing through and answering questions. And people have
Speaker 1: also been looking at the subtle detection of stress in
Speaker 1: the voi, the way that your voice gets constricted when
Speaker 1: you have stress overlying about something. But things get a
Speaker 1: little more interesting and spicy when we start looking directly
Speaker 1: at signals of the brain, and one of these technologies
Speaker 1: involves sticking electrodes on the outside of the scalp, and
Speaker 1: this is known as electron cepholography or EEG. And the
Speaker 1: idea here is to use things like the guilty knowledge
Speaker 1: test to see if there's a big brain response when
Speaker 1: the person sees something they are familiar with. So let's
Speaker 1: go back to that story that I began with about
Speaker 1: Aditi Sharma and her boyfriend Pravine, who together killed her fiance.
Speaker 1: In Aditi's court trial in two thousand and eight, she
Speaker 1: was tested with a thirty two electrode system on her
Speaker 1: head called the Brain Electrical Oscillations Signature system. And the
Speaker 1: way it worked is this, a forensic scientist had a
Speaker 1: dit listen to a voice talk about the alleged murder
Speaker 1: and when she heard specific incriminating bits of the story
Speaker 1: about how the murder was committed. For example, he was
Speaker 1: killed with a special kind of drink in McDonald's that
Speaker 1: was poisoned with arsenic When she heard those bits of
Speaker 1: the story, woosh, her brain had larger activity, which was
Speaker 1: interpreted as the activation of memories that she had of
Speaker 1: concealed knowledge, so this was presented as evidence of her
Speaker 1: guilt in this case. Now, I think all legal scholars
Speaker 1: agree that this was not the only evidence on which
Speaker 1: her guilty verdict was based. There were other pieces of
Speaker 1: evidence that pointed to her guilt. But nonetheless, this kindled
Speaker 1: an ongoing controversy about when and whether it makes sense
Speaker 1: to accept lie detector technology in a court of law,
Speaker 1: because this was one of the first cases, possibly the
Speaker 1: very first, where someone was convicted in part on brain
Speaker 1: based lie detection. But this really was just the beginning,
Speaker 1: because starting over two decades ago, people got interested in
Speaker 1: the idea of whether you could detect a lie in
Speaker 1: a brain scanner, and in two thousand and six at
Speaker 1: least two companies launched with this goal. There was no
Speaker 1: Lie MRI in San Diego and Cephos Corporation in Massachusetts,
Speaker 1: and their mission was using brain scanning fMRI or functional
Speaker 1: magnetic resonance imaging for the purpose of lie detection. Now,
Speaker 1: how do these companies come about, Well, they were based
Speaker 1: on the discovery that when you are lying, you can
Speaker 1: image in the scanner more activity in frontal brain areas
Speaker 1: just behind the forehead, more activity than when you are
Speaker 1: telling the truth. In other words, while it's easy to
Speaker 1: blurt out the truth, lying requires more effort. You are
Speaker 1: inhibiting telling the truth. You don't want to blurt out
Speaker 1: the truth, and you have to generate falsified data. Remember
Speaker 1: I mentioned earlier that it's easier to tell the truth,
Speaker 1: and we see that reflected in brain activity. So back
Speaker 1: in two thousand and one, a researcher named Sean Spence
Speaker 1: and his colleagues interviewed participants on what activities they had
Speaker 1: done the previous day. Then in the scanner fMRI, these
Speaker 1: people were presented with various activities and were asked whether
Speaker 1: they had done them, and they had two buttons, a
Speaker 1: yes and a no. Now, they were also given either
Speaker 1: a red light or a green light to tell them
Speaker 1: whether they should lie or not on this round. So
Speaker 1: the first thing the researchers noted is that it always
Speaker 1: takes longer to lie, about a fifth of a second longer.
Speaker 1: So you went to the beach yesterday, and you're asked
Speaker 1: if you went to the beach, But you see that
Speaker 1: there's a red light and so you answer no. Now,
Speaker 1: the first thing the researchers noted is that it always
Speaker 1: takes longer to lie, about a fifth of a second longer,
Speaker 1: And this is consistent with the idea that you are
Speaker 1: taking an answer you already know and you're squelching that.
Speaker 1: So they demonstrated that this squelching of the truth response
Speaker 1: activates an area called the ventralateral prefrontal cortex. This is
Speaker 1: a region that becomes active when you need to suppress
Speaker 1: a behavior that you would normally just go with, in
Speaker 1: this case telling the truth, and other brain areas are
Speaker 1: involved too. So there was a study Bilangualmen in colleagues
Speaker 1: the next year where participants went into the scanner and
Speaker 1: they saw a playing card on the screen and they
Speaker 1: were asked to remember it like Ace of Spades. Then
Speaker 1: they were shown a series of cards and they were asked,
Speaker 1: was that your card or not? They were instructed to
Speaker 1: lie sometimes, and here's the key. When they lied, the
Speaker 1: researcher saw a lot of activity in an area called
Speaker 1: the anterior singular cortex, which is a region that becomes
Speaker 1: active when there's con between other brain areas. So in
Speaker 1: both of those studies, people were just saying yes or no.
Speaker 1: But in the next study by Spence and colleagues, they
Speaker 1: wanted to see what happens when people get more imaginative,
Speaker 1: when they go beyond yes or no to make up
Speaker 1: a new story. So imagine I ask you where were
Speaker 1: you on the afternoon of March first, and you know
Speaker 1: the answer to that, But imagine that you lie to
Speaker 1: me and you say, oh, I left my cell phone
Speaker 1: in the car and I was just hiking by myself
Speaker 1: up the mountain. Now, in order to do that lie,
Speaker 1: you have to think of the true response and suppress that,
Speaker 1: and then you have to cook something up. So when
Speaker 1: you are thinking of the truth, but you actively suppress that,
Speaker 1: that activates the ventralateral prefrontal cortex, as we just saw.
Speaker 1: But then you need to generate the lie, and this
Speaker 1: activates the dorsal lateral prefrontal cortex, which is an area
Speaker 1: that cranks up when a person generates something new, like
Speaker 1: a new response that they hadn't done before. And we
Speaker 1: see other areas too, like the anterior singular cortex, which
Speaker 1: cares about conflict, and the venturemedial prefrontal cortex, which cranks
Speaker 1: up when you're trying to regulate your emotions. So there
Speaker 1: are a whole constellation of brain areas that indicate deception. Now, interestingly,
Speaker 1: in all these studies about lying, you never see areas
Speaker 1: where there's more activity when you tell the truth. There's
Speaker 1: only more activity when you're lying. So the idea that
Speaker 1: it's easier to tell the truth holds as a rule
Speaker 1: in life and as a rule in the brain. Now,
Speaker 1: that's how you can detect something about deception using an fMRI,
Speaker 1: and you can also use the guilty knowledge technique here.
Speaker 1: So one research paper said, we're going to try a
Speaker 1: guilty knowledge technique. We're going to rennew certain dates on
Speaker 1: the calendar, and one of those dates is going to
Speaker 1: be your birth birthday, and of course all the participants
Speaker 1: have different birthdays, so it's a nicely controlled study. So
Speaker 1: the murder weapon they're looking for is your birthday. So
Speaker 1: they say March twelfth, November twenty third, August fifth, and
Speaker 1: at some point they say your birthday and several eras
Speaker 1: in your brain light up. You're hearing something that is
Speaker 1: familiar to you. And generally this is the same thing
Speaker 1: that happens when you see that Pokemon statue or when
Speaker 1: you see the murder weapon that you used. Now, it
Speaker 1: turns out that in this study, the investigators reported that
Speaker 1: this worked one hundred percent of the time. In other words,
Speaker 1: all the time they could tell when someone is hearing
Speaker 1: their birthday versus hearing another date. But it turns out
Speaker 1: that you can easily fake the test. You can fool
Speaker 1: this entirely by saying in advance, Okay, I'm going to
Speaker 1: associate another date with a small movement of my finger,
Speaker 1: So you decide that before you go into the test,
Speaker 1: and then when you hear August fifth, you were waiting
Speaker 1: to hear that so you could move your finger. So
Speaker 1: when you hear it, your brain has a big response
Speaker 1: because you were waiting for that. What that means is
Speaker 1: that you're having the same murder weapon response to some
Speaker 1: arbitrary date or any number of arbitrary dates, because you
Speaker 1: have pre planned that you were going to do that,
Speaker 1: you were waiting to hear that target, and as a result,
Speaker 1: everything else gets swamped out because you're having the same
Speaker 1: response to some fake date as you are to the
Speaker 1: real date, and you can't tell a difference between those
Speaker 1: brain states. So it turns out that this is not
Speaker 1: ready for the courts, because you can completely fool this
Speaker 1: with a very simple countermeasure, and even with the other
Speaker 1: fMRI technique that just involves looking for the correlates of deception.
Speaker 1: It only works if you stay absolutely still in the scanner.
Speaker 1: And even if someone were to fix your head into
Speaker 1: place so that you couldn't move at all, you could,
Speaker 1: of course do all kinds of things to think random
Speaker 1: thoughts and move your fingers and almost certainly swamp out
Speaker 1: any meaningful signals. So let's recap where we are. As
Speaker 1: animals developed bigger brains, they were able to make better
Speaker 1: models of one another, and that allowed them to cooperate,
Speaker 1: but it also allowed them to deceive. And so throughout
Speaker 1: human history people have been very interested in the question
Speaker 1: of whether you can detect if a person is lying.
Speaker 1: And this is tough because someone can be telling the
Speaker 1: truth but they're factually incorrect. But if they believe their
Speaker 1: story is true, then you would say, look, she passed
Speaker 1: the polygraph test, she passed the brain scan lie detection test,
Speaker 1: but it still doesn't tell you what actually happened. All
Speaker 1: it's telling you is that she believes that would happened.
Speaker 1: But sometimes people really do set out to deceive, and
Speaker 1: that's what people want to build technologies for. And we
Speaker 1: find this search for detecting deception all over. Sometimes this
Speaker 1: is in arbitration situations where it's one person's word against
Speaker 1: another and you want to know who's telling the truth.
Speaker 1: And you find this in criminal cases where attorneys want
Speaker 1: to know if someone has in fact broken the law.
Speaker 1: And you find this in national security where governments want
Speaker 1: to know when some spy that they've caught is telling
Speaker 1: the truth or not. They want to have a meaningful interrogation. Now,
Speaker 1: as a reminder of what we talked about, there's no
Speaker 1: way to measure a lie directly. All we ever measure
Speaker 1: is the physiology that's associated with the lie, whether that's
Speaker 1: a stress response like we see in the polygraph test,
Speaker 1: or whether it's about inhibiting the truth and cooking up
Speaker 1: a fake story like we see in brain imaging. But
Speaker 1: the question is will it work? Will we ever get
Speaker 1: to a point where we can know for sure when
Speaker 1: somebody is lying. Essentially, the debate about this falls into
Speaker 1: two camps. The first is that this technology simply is
Speaker 1: never going to work perfectly in the real world because
Speaker 1: it's always facing a mountain of questions. What if the
Speaker 1: person that you're measuring is on some sort of medication,
Speaker 1: What if he's had a stroke. Does the technology work
Speaker 1: for people who are outside the narrow age range that's
Speaker 1: been studied so far. What about psychopaths and compulsive liars.
Speaker 1: What if a person is totally misremembered something but they're
Speaker 1: not actually lying, and on on. So the concern that
Speaker 1: many scholars express is that these technologies, both new and old,
Speaker 1: will appear in courts before all the wrinkles have been
Speaker 1: ironed out. And this is a concern for many reasons.
Speaker 1: But when it comes to fMRI, one of the concerns
Speaker 1: is that images of the brain are very compelling to jurors.
Speaker 1: It's different if you just say, hey, on this polygraph test,
Speaker 1: there was a blip, versus you show a beautiful false
Speaker 1: color image of the brain, and then a juror thinks, wow, wow,
Speaker 1: that looks like real science, even if the accuracy probability
Speaker 1: is the same. So that's the first concern is that
Speaker 1: this technology is not actually going to work in the
Speaker 1: real world. The second concern is that it will work,
Speaker 1: and this is a concern because most people hold the
Speaker 1: intuition that the inside of your head should be inviolable.
Speaker 1: Your mind should be a sanctuary where no one can
Speaker 1: enter so given that even if the technology does work
Speaker 1: perfectly someday, there are several reasons why it might never
Speaker 1: get used in the legal system. I mentioned the Seffer
Speaker 1: case in nineteen ninety eight when the Supreme Court was
Speaker 1: deciding on whether a lower court has to accept the
Speaker 1: polygraph test, and at that time four of the justices
Speaker 1: suggested that even if polygraph tests were to work flawlessly
Speaker 1: with one hundred percent reliability, they still shouldn't be admitted.
Speaker 1: Why because the justice is said that would take away
Speaker 1: the job of the jury as the determiners of truth.
Speaker 1: Now that's not law, it's only a legal opinion at
Speaker 1: this stage, but it could be a pattern for how
Speaker 1: fancy brain imaging technologies might also get ruled on in
Speaker 1: the future. And again, unlike a polygraph as it stands now,
Speaker 1: the fMRI technology won't work unless you are a willing subject,
Speaker 1: willing to keep your head very still for the images
Speaker 1: to come out right. And in this sense, the current
Speaker 1: brain imaging technology may become more useful as a truth
Speaker 1: confirmer by people who feel they've been falsely accused, rather
Speaker 1: than a lie detector. So let's return to this issue
Speaker 1: about privacy and whether lie detection as it gets better
Speaker 1: over the coming centuries, constitutes a violation. One of the
Speaker 1: deepest questions from the point of view of the legal
Speaker 1: system in the Constitution is that a criminal defendant always
Speaker 1: retains the right not to testify and not to incriminate himself.
Speaker 1: So can a brain scan lie detection test be forced
Speaker 1: or does it need to be agreed to? If you
Speaker 1: were to refuse to use a new brain scan technology,
Speaker 1: are you protected against self incrimination which is the fifth
Speaker 1: Amendment of the Constitution. There's a lot of legal precedent
Speaker 1: to all these questions, but of course we don't know
Speaker 1: exactly how this will evolve in the coming decades. Currently,
Speaker 1: blood tests and DNA tests can be forced. Many counties
Speaker 1: have a no refusal policy. If you're driving through and
Speaker 1: they suspect you of being on drugs, they can draw
Speaker 1: your blood. In other circumstances, law enforcement gets a court
Speaker 1: order for your DNA, which is usually taken with a
Speaker 1: cheek swab. Now, these tests can only be done if
Speaker 1: they are very relevant to the case, if they're critical
Speaker 1: to the outcome. So will brain scan lie detection tests
Speaker 1: ever reach the point where they can be forced, Well,
Speaker 1: it's difficult to say, but as a piece of legal
Speaker 1: precedent that might be applicable. Let's go back to nineteen
Speaker 1: fifty two. There was a man in California named Rochin,
Speaker 1: and the police raided his home on suspicion that he
Speaker 1: had narcotics. And when they busted in, he went running
Speaker 1: up the stairs and they chased him up the stairs
Speaker 1: and he got to his bedroom and there were some
Speaker 1: pills on the dresser and they said what is that
Speaker 1: and he popped the pills into his mouth and swallowed them.
Speaker 1: So this made the police mad because he had just
Speaker 1: gotten rid of the evidence. So they wrestled him to
Speaker 1: try to get the pills out, and when that didn't work,
Speaker 1: they handcuffed him and they took him down to the
Speaker 1: emergency room and had his stomach pumped to get the
Speaker 1: evidence back out. And this case spun all the way
Speaker 1: to the Supreme Court, and the court concluded, you can't
Speaker 1: do that. You can't pump somebody's stomach to get the
Speaker 1: evidence out of them. Why because they said that is
Speaker 1: unreasonable search seizure, and they said it shocks the conscience.
Speaker 1: So given this legal background, it's not clear that you
Speaker 1: could be forced into giving a brain scan and whether
Speaker 1: that would count as a form of unreasonable search and seizure.
Speaker 1: Would it be like pumping out the contents of the
Speaker 1: stomach if you looked at the contents of your mental life.
Speaker 1: And what if you're terrified of a brain scanner because
Speaker 1: you have claustrophobia or you don't like loud noise. Could
Speaker 1: you say that you're being put under undue pressure and
Speaker 1: it's a form of torture. So these are all open questions.
Speaker 1: Can a legal system in the future get a mental
Speaker 1: search warrant? Does that seem reasonable under some circumstances? Or
Speaker 1: is there something special about this inner sanctum which has
Speaker 1: been absolutely private for all of history? Can we and
Speaker 1: should we maintain that expectation. How all of this is
Speaker 1: going to shake out at the intersection of neuroscience and
Speaker 1: the legal system is It's difficult to say at the moment,
Speaker 1: but generally, as our technology moves faster and faster and
Speaker 1: surpasses our stone age brains, we find ourselves entering a
Speaker 1: very strange new world, and that is no lie. Go
Speaker 1: to Eagleman dot com slash podcast for more information and
Speaker 1: to find further reading. Always feel free to send me
Speaker 1: an email at podcasts at eagleman dot com with any questions,
Speaker 1: and check out and subscribe to Inner Cosmos on YouTube
Speaker 1: for videos of each episode and to leave comments. Until
Speaker 1: next time. I'm David Eagleman and this is Inner Cosmos