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How do lie detectors work?
Experts explain how lie detectors work, what happens in the brain when we tell lies and how accurate polygraph tests are.
- In a 2002 study, 60 percent of people were found to lie at least once during a 10-minute conversation, with most people telling an average of two or three lies. The polygraph, invented in the early 1920s, detects physiological responses to lying (such as elevated heart and respiratory rates as well as spikes in blood pressure.
- Three main areas of the brain are stimulated during deception: the frontal lobe, the limbic system, and the temporal lobe.
- According to the American Polygraph Association, the estimated accuracy of a polygraph can be up to 87 percent.
What happens in your brain when you lie?
Image by Shidlovski on Shutterstock
We all lie. Some might argue it's human nature. In a 2002 study, 60 percent of people were found to lie at least once during a 10-minute conversation, with most people telling an average of two or three lies. Some lies are small, some are bigger, some are done out of kindness, and some done out of malice. But a lie is a lie, and the way that your body reacts when you lie is the same.
Lying is an inherently stressful activity.
When you engage in a false narrative (or a lie), your respiratory and heart rate will increase and you may even start to sweat. While people may vary in the ability to tell a lie, most of the time your body will react in this same way. Exceptions to this rule are, for example, psychopaths, who lack empathy and therefore do not exhibit the typical physiological stress responses when telling a lie.
Brain imaging studies have shown what really happens in the brain when you tell a lie.
Lying generally involves more effort than telling the truth, and because of this, it involves the prefrontal cortex. A 2001 study by late neuroscientist Sean Spence (University of Sheffield in England) explored fMRI images of the brain while lying. Participants answered questions about their daily routine by pressing a yes or no button on a screen. Depending on the color of the writing, they were to answer either truthfully or with a lie.
The results showed participants needed more time to formulate a dishonest answer than an honest one, and certain parts of the prefrontal cortex were more active when they were lying.
Further research explains that three main areas of the brain are stimulated during deception - the frontal lobe works to suppress the truth, the limbic system activates due to the anxiety that comes from lying, and the temporal lobe activates in response to retrieving memories and creating mental imagery (fabricating a believable lie).
Research also suggests lying becomes easier the more you do it.
In a 2016 study, Duke psychologist Dan Ariely and his colleagues showed how dishonesty can alter your brain, making it easier to tell lies in the future. When people told lies, the scientists noticed a burst of activity in the amygdala, the part of the brain involved in fear, anxiety, and emotional responses. When the scientists had their subject play a game in which they won money by deceiving their partner, they noticed the negative signals from the amygdala begin to decrease.
"Lying, in fact, desensitized your brain to the fear of getting caught of hurting others, making lying for your own benefit down the road much easier," wrote Jessica Stillman for INC.
How do lie detectors work?
The polygraph will be able to detect if someone is telling the truth 87 percent of the time.
Image by OllivsArt on Shutterstock
In 1921, a California-based police officer and physiologist John A. Larson created an apparatus that simultaneously measures continuous changes in blood pressure, heart rate, and respiration rate to aid in the detection of deception. This was the invention of the polygraph, which is commonly referred to as a lie detector.
Seven years before this, in 1914, an Italian psychologist (Vittorio Benussi) published findings on "the respiratory symptoms of a lie," and in 1915, an American psychologist and lawyer (William M. Marston) invented a blood pressure test for the detection of deception.
The accuracy of polygraph tests has been called into question for nearly as long as they've existed. These machines detect typical stress responses to telling a lie. This means increased heart rate, blood pressure, and respiration rate. Some people are naturally good liars, or become better with controlling these stress responses, and can manage to stay calm during a lie detector test.
According to the American Polygraph Association (made up largely of polygraph examiners), the estimated accuracy of a polygraph can be up to 87 percent. That means that in 87 out of 100 cases, the polygraph will be able to detect if someone is telling the truth.
If the person lies but doesn't have the stress symptoms of telling that lie, they will pass the test. Similarly, innocent people may fail the test due to being anxious about taking it to begin with and therefore emitting the elevated heart, respiratory, and blood pressure rates that can be detected.
- Is it Lying that Makes Us Truly Human? - Big Think ›
- Lie Detectors: The return of trial by ordeal - Big Think ›
- How to Outsmart a Lie Detector Test - Big Think ›
Scientists are using bioelectronic medicine to treat inflammatory diseases, an approach that capitalizes on the ancient "hardwiring" of the nervous system.
- Bioelectronic medicine is an emerging field that focuses on manipulating the nervous system to treat diseases.
- Clinical studies show that using electronic devices to stimulate the vagus nerve is effective at treating inflammatory diseases like rheumatoid arthritis.
- Although it's not yet approved by the US Food and Drug Administration, vagus nerve stimulation may also prove effective at treating other diseases like cancer, diabetes and depression.
The nervous system’s ancient reflexes<p>You accidentally place your hand on a hot stove. Almost instantaneously, your hand withdraws.</p><p>What triggered your hand to move? The answer is <em>not</em> that you consciously decided the stove was hot and you should move your hand. Rather, it was a reflex: Skin receptors on your hand sent nerve impulses to the spinal cord, which ultimately sent back motor neurons that caused your hand to move away. This all occurred before your "conscious brain" realized what happened.</p><p>Similarly, the nervous system has reflexes that protect individual cells in the body.</p><p>"The nervous system evolved because we need to respond to stimuli in the environment," said Dr. Tracey. "Neural signals don't come from the brain down first. Instead, when something happens in the environment, our peripheral nervous system senses it and sends a signal to the central nervous system, which comprises the brain and spinal cord. And then the nervous system responds to correct the problem."</p><p>So, what if scientists could "hack" into the nervous system, manipulating the electrical activity in the nervous system to control molecular processes and produce desirable outcomes? That's the chief goal of bioelectronic medicine.</p><p>"There are billions of neurons in the body that interact with almost every cell in the body, and at each of those nerve endings, molecular signals control molecular mechanisms that can be defined and mapped, and potentially put under control," Dr. Tracey said in a <a href="https://www.youtube.com/watch?v=AJH9KsMKi5M" target="_blank">TED Talk</a>.</p><p>"Many of these mechanisms are also involved in important diseases, like cancer, Alzheimer's, diabetes, hypertension and shock. It's very plausible that finding neural signals to control those mechanisms will hold promises for devices replacing some of today's medication for those diseases."</p><p>How can scientists hack the nervous system? For years, researchers in the field of bioelectronic medicine have zeroed in on the longest cranial nerve in the body: the vagus nerve.</p>
The vagus nerve<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYyOTM5OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NTIwNzk0NX0.UCy-3UNpomb3DQZMhyOw_SQG4ThwACXW_rMnc9mLAe8/img.jpg?width=1245&coordinates=0%2C0%2C0%2C0&height=700" id="09add" class="rm-shortcode" data-rm-shortcode-id="f38dbfbbfe470ad85a3b023dd5083557" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="700" />
Electrical signals, seen here in a synapse, travel along the vagus nerve to trigger an inflammatory response.
Credit: Adobe Stock via solvod<p>The vagus nerve ("vagus" meaning "wandering" in Latin) comprises two nerve branches that stretch from the brainstem down to the chest and abdomen, where nerve fibers connect to organs. Electrical signals constantly travel up and down the vagus nerve, facilitating communication between the brain and other parts of the body.</p><p>One aspect of this back-and-forth communication is inflammation. When the immune system detects injury or attack, it automatically triggers an inflammatory response, which helps heal injuries and fend off invaders. But when not deployed properly, inflammation can become excessive, exacerbating the original problem and potentially contributing to diseases.</p><p>In 2002, Dr. Tracey and his colleagues discovered that the nervous system plays a key role in monitoring and modifying inflammation. This occurs through a process called the <a href="https://www.nature.com/articles/nature01321" target="_blank" rel="noopener noreferrer">inflammatory reflex</a>. In simple terms, it works like this: When the nervous system detects inflammatory stimuli, it reflexively (and subconsciously) deploys electrical signals through the vagus nerve that trigger anti-inflammatory molecular processes.</p><p>In rodent experiments, Dr. Tracey and his colleagues observed that electrical signals traveling through the vagus nerve control TNF, a protein that, in excess, causes inflammation. These electrical signals travel through the vagus nerve to the spleen. There, electrical signals are converted to chemical signals, triggering a molecular process that ultimately makes TNF, which exacerbates conditions like rheumatoid arthritis.</p><p>The incredible chain reaction of the inflammatory reflex was observed by Dr. Tracey and his colleagues in greater detail through rodent experiments. When inflammatory stimuli are detected, the nervous system sends electrical signals that travel through the vagus nerve to the spleen. There, the electrical signals are converted to chemical signals, which trigger the spleen to create a white blood cell called a T cell, which then creates a neurotransmitter called acetylcholine. The acetylcholine interacts with macrophages, which are a specific type of white blood cell that creates TNF, a protein that, in excess, causes inflammation. At that point, the acetylcholine triggers the macrophages to stop overproducing TNF – or inflammation.</p><p>Experiments showed that when a specific part of the body is inflamed, specific fibers within the vagus nerve start firing. Dr. Tracey and his colleagues were able to map these relationships. More importantly, they were able to stimulate specific parts of the vagus nerve to "shut off" inflammation.</p><p>What's more, clinical trials show that vagus nerve stimulation not only "shuts off" inflammation, but also triggers the production of cells that promote healing.</p><p>"In animal experiments, we understand how this works," Dr. Tracey said. "And now we have clinical trials showing that the human response is what's predicted by the lab experiments. Many scientific thresholds have been crossed in the clinic and the lab. We're literally at the point of regulatory steps and stages, and then marketing and distribution before this idea takes off."<br></p>
The future of bioelectronic medicine<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYxMDYxMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNjQwOTExNH0.uBY1TnEs_kv9Dal7zmA_i9L7T0wnIuf9gGtdRXcNNxo/img.jpg?width=980" id="8b5b2" class="rm-shortcode" data-rm-shortcode-id="c005e615e5f23c2817483862354d2cc4" data-rm-shortcode-name="rebelmouse-image" data-width="2000" data-height="1125" />
Vagus nerve stimulation can already treat Crohn's disease and other inflammatory diseases. In the future, it may also be used to treat cancer, diabetes, and depression.
Credit: Adobe Stock via Maridav<p>Vagus nerve stimulation is currently awaiting approval by the US Food and Drug Administration, but so far, it's proven safe and effective in clinical trials on humans. Dr. Tracey said vagus nerve stimulation could become a common treatment for a wide range of diseases, including cancer, Alzheimer's, diabetes, hypertension, shock, depression and diabetes.</p><p>"To the extent that inflammation is the problem in the disease, then stopping inflammation or suppressing the inflammation with vagus nerve stimulation or bioelectronic approaches will be beneficial and therapeutic," he said.</p><p>Receiving vagus nerve stimulation would require having an electronic device, about the size of lima bean, surgically implanted in your neck during a 30-minute procedure. A couple of weeks later, you'd visit, say, your rheumatologist, who would activate the device and determine the right dosage. The stimulation would take a few minutes each day, and it'd likely be unnoticeable.</p><p>But the most revolutionary aspect of bioelectronic medicine, according to Dr. Tracey, is that approaches like vagus nerve stimulation wouldn't come with harmful and potentially deadly side effects, as many pharmaceutical drugs currently do.</p><p>"A device on a nerve is not going to have systemic side effects on the body like taking a steroid does," Dr. Tracey said. "It's a powerful concept that, frankly, scientists are quite accepting of—it's actually quite amazing. But the idea of adopting this into practice is going to take another 10 or 20 years, because it's hard for physicians, who've spent their lives writing prescriptions for pills or injections, that a computer chip can replace the drug."</p><p>But patients could also play a role in advancing bioelectronic medicine.</p><p>"There's a huge demand in this patient cohort for something better than they're taking now," Dr. Tracey said. "Patients don't want to take a drug with a black-box warning, costs $100,000 a year and works half the time."</p><p>Michael Dowling, president and CEO of Northwell Health, elaborated:</p><p>"Why would patients pursue a drug regimen when they could opt for a few electronic pulses? Is it possible that treatments like this, pulses through electronic devices, could replace some drugs in the coming years as preferred treatments? Tracey believes it is, and that is perhaps why the pharmaceutical industry closely follows his work."</p><p>Over the long term, bioelectronic approaches are unlikely to completely replace pharmaceutical drugs, but they could replace many, or at least be used as supplemental treatments.</p><p>Dr. Tracey is optimistic about the future of the field.</p><p>"It's going to spawn a huge new industry that will rival the pharmaceutical industry in the next 50 years," he said. "This is no longer just a startup industry. [...] It's going to be very interesting to see the explosive growth that's going to occur."</p>
The first rule of Vulture Club: stay out of Portugal.
So you're a vulture, riding the thermals that rise up over Iberia. Your way of life is ancient, ruled by needs and instincts that are way older than the human civilization that has overtaken the peninsula below, and the entire planet.
"The Expanse" is the best vision I've ever seen of a space-faring future that may be just a few generations away.
- Want three reasons why that headline is justified? Characters and acting, universe building, and science.
- For those who don't know, "The Expanse" is a series that's run on SyFy and Amazon Prime set about 200 years in the future in a mostly settled solar system with three waring factions: Earth, Mars, and Belters.
- No other show I know of manages to use real science so adeptly in the service of its story and its grand universe building.
Credit: "The Expanse" / Syfy<p>Now, I get it if you don't agree with me. I love "Star Trek" and I thought "Battlestar Galactica" (the new one) was amazing and I do adore "The Mandalorian". They are all fun and important and worth watching and thinking about. And maybe you love them more than anything else. But when you sum up the acting, the universe building, and the use of real science where it matters, I think nothing can beat "The Expanse". And with a <a href="https://www.rottentomatoes.com/tv/the_expanse" target="_blank">Rotten Tomato</a> average rating of 93%, I'm clearly not the only one who feels this way.</p><p>Best.</p><p>Show.</p><p>Ever. </p>
Contrary to what some might think, the brain is a very plastic organ.
As with many other physicians, recommending physical activity to patients was just a doctor chore for me – until a few years ago. That was because I myself was not very active.