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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 ›
The finding is remarkably similar to the Dunning-Kruger effect, which describes how incompetent people tend to overestimate their own competency.
- Recent studies asked participants to rate the attractiveness of themselves and other participants, who were strangers.
- The studies kept yielding the same finding: unattractive people overestimate their attractiveness, while attractive people underrate their looks.
- Why this happens is unclear, but it doesn't seem to be due to a general inability to judge attractiveness.
There's no shortage of disparities between attractive and unattractive people. Studies show that the best-looking among us tend to have an easier time making money, receiving help, avoiding punishment, and being perceived as competent. (Sure, research also suggests beautiful people have shorter relationships, but they also have more sexual partners, and more options for romantic relationships. So call it a wash.)
Now, new research reveals another disparity: Unattractive people seem less able to accurately judge their own attractiveness, and they tend to overestimate their looks. In contrast, beautiful people tend to rate themselves more accurately. If anything, they underestimate their attractiveness.
The research, published in the Scandinavian Journal of Psychology, involved six studies that asked participants to rate the attractiveness of themselves and other participants, who were strangers. The studies also asked participants to predict how others might rate them.
In the first study, lead author Tobias Greitemeyer found that the participants who were most likely to overestimate their attractiveness were among the least attractive people in the study, based on average ratings.
Ratings of subjective attractiveness as a function of the participant's objective attractiveness (Study 1)
"Overall, unattractive participants judged themselves to be of about average attractiveness and they showed very little awareness that strangers do not share this view. In contrast, attractive participants had more insights into how attractive they actually are. [...] It thus appears that unattractive people maintain illusory self‐perceptions of their attractiveness, whereas attractive people's self‐views are more grounded in reality."
Why do unattractive people overestimate their attractiveness? Could it be because they want to maintain a positive self-image, so they delude themselves? After all, previous research has shown that people tend to discredit or "forget" negative social feedback, which seems to help protect a sense of self-worth.
To find out, Greitemeyer conducted a study that aimed to put participants in a positive, non-defensive mindset before rating attractiveness. He did that by asking participants questions that affirmed parts of their personality that had nothing to do with physical appearance, such as: "Have you ever been generous and selfless to another person?" Yet, this didn't change how participants rated themselves, suggesting that unattractive people aren't overestimating their looks out of defensiveness.
The studies kept yielding the same finding: unattractive people overestimate their attractiveness. Does that bias sound familiar? If so, you might be thinking of the Dunning-Kruger effect, which describes how incompetent people tend to overestimate their own competency. Why? Because they lack the metacognitive skills needed to discern their own shortcomings.
Greitemeyer found that unattractive people were worse at differentiating between attractive and unattractive people. But the finding that unattractive people may have different beauty ideals (or, more plainly, weaker ability to judge attractiveness) did "not have an impact on how they perceive themselves."
In short, it remains a mystery exactly why unattractive people overestimate their looks. Greitemeyer concluded that, while most people are decent at judging the attractiveness of others, "it appears that those who are unattractive do not know that they are unattractive."
Unattractive people aren't completely unaware
The results of one study suggested that unattractive people aren't completely in the dark about their looks. In the study, unattractive people were shown a set of photos of highly attractive and unattractive people, and they were asked to select photos of people with comparable attractiveness. Most unattractive people chose to compare themselves with similarly unattractive people.
"The finding that unattractive participants selected unattractive stimulus persons with whom they would compare their attractiveness to suggests that they may have an inkling that they are less attractive than they want it to be," Greitemeyer wrote.
Every star we can see, including our sun, was born in one of these violent clouds.
This article was originally published on our sister site, Freethink.
An international team of astronomers has conducted the biggest survey of stellar nurseries to date, charting more than 100,000 star-birthing regions across our corner of the universe.
Stellar nurseries: Outer space is filled with clouds of dust and gas called nebulae. In some of these nebulae, gravity will pull the dust and gas into clumps that eventually get so big, they collapse on themselves — and a star is born.
These star-birthing nebulae are known as stellar nurseries.
The challenge: Stars are a key part of the universe — they lead to the formation of planets and produce the elements needed to create life as we know it. A better understanding of stars, then, means a better understanding of the universe — but there's still a lot we don't know about star formation.
This is partly because it's hard to see what's going on in stellar nurseries — the clouds of dust obscure optical telescopes' view — and also because there are just so many of them that it's hard to know what the average nursery is like.
The survey: The astronomers conducted their survey of stellar nurseries using the massive ALMA telescope array in Chile. Because ALMA is a radio telescope, it captures the radio waves emanating from celestial objects, rather than the light.
"The new thing ... is that we can use ALMA to take pictures of many galaxies, and these pictures are as sharp and detailed as those taken by optical telescopes," Jiayi Sun, an Ohio State University (OSU) researcher, said in a press release.
"This just hasn't been possible before."
Over the course of the five-year survey, the group was able to chart more than 100,000 stellar nurseries across more than 90 nearby galaxies, expanding the amount of available data on the celestial objects tenfold, according to OSU researcher Adam Leroy.
New insights: The survey is already yielding new insights into stellar nurseries, including the fact that they appear to be more diverse than previously thought.
"For a long time, conventional wisdom among astronomers was that all stellar nurseries looked more or less the same," Sun said. "But with this survey we can see that this is really not the case."
"While there are some similarities, the nature and appearance of these nurseries change within and among galaxies," he continued, "just like cities or trees may vary in important ways as you go from place to place across the world."
Astronomers have also learned from the survey that stellar nurseries aren't particularly efficient at producing stars and tend to live for only 10 to 30 million years, which isn't very long on a universal scale.
Looking ahead: Data from the survey is now publicly available, so expect to see other researchers using it to make their own observations about stellar nurseries in the future.
"We have an incredible dataset here that will continue to be useful," Leroy said. "This is really a new view of galaxies and we expect to be learning from it for years to come."
Tiny specks of space debris can move faster than bullets and cause way more damage. Cleaning it up is imperative.
- NASA estimates that more than 500,000 pieces of space trash larger than a marble are currently in orbit. Estimates exceed 128 million pieces when factoring in smaller pieces from collisions. At 17,500 MPH, even a paint chip can cause serious damage.
- To prevent this untrackable space debris from taking out satellites and putting astronauts in danger, scientists have been working on ways to retrieve large objects before they collide and create more problems.
- The team at Clearspace, in collaboration with the European Space Agency, is on a mission to capture one such object using an autonomous spacecraft with claw-like arms. It's an expensive and very tricky mission, but one that could have a major impact on the future of space exploration.
This is the first episode of Just Might Work, an original series by Freethink, focused on surprising solutions to our biggest problems.
Catch more Just Might Work episodes on their channel: https://www.freethink.com/shows/just-might-work