Maybe eyes really are windows into the soul — or at least into the brain, as a new study finds.
- Researchers find a correlation between pupil size and differences in cognitive ability.
- The larger the pupil, the higher the intelligence.
- The explanation for why this happens lies within the brain, but more research is needed.
What can you tell by looking into someone's eyes? You can spot a glint of humor, signs of tiredness, or maybe that they don't like something or someone.
But outside of assessing an emotional state, a person's eyes may also provide clues about their intelligence, suggests new research. A study carried out at the Georgia Institute of Technology shows that pupil size is "closely related" to differences in intelligence between individuals.
The scientists found that larger pupils may be connected to higher intelligence, as demonstrated by tests that gauged reasoning skills, memory, and attention. In fact, the researchers claim that the relationship of intelligence to pupil size is so pronounced, that it came across their previous two studies as well and can be spotted just with your naked eyes, without any additional scientific instruments. You should be able to tell who scored the highest or the lowest on the cognitive tests just by looking at them, say the researchers.
The pupil-IQ link
The connection was first noticed across memory tasks, looking at pupil dilations as signs of mental effort. The studies involved more than 500 people aged 18 to 35 from the Atlanta area. The subjects' pupil sizes were measured by eye trackers, which use a camera and a computer to capture light reflecting off the pupil and cornea. As the scientists explained in Scientific American, pupil diameters range from two to eight millimeters. To determine average pupil size, they took measurements of the pupils at rest when the participants were staring at a blank screen for a few minutes.
Another part of the experiment involved having the subjects take a series of cognitive tests that evaluated "fluid intelligence" (the ability to reason when confronted with new problems), "working memory capacity" (how well people could remember information over time), and "attention control" (the ability to keep focusing attention even while being distracted). An example of the latter involves a test that attempts to divert a person's focus on a disappearing letter by showing a flickering asterisk on another part of the screen. If a person pays too much attention to the asterisk, they might miss the letter.
The conclusions of the research were that having a larger baseline pupil size was related to greater fluid intelligence, having more attention control, and even greater working memory capacity, although to a smaller extent. In an email exchange with Big Think, author Jason Tsukahara pointed out, "It is important to consider that what we find is a correlation — which should not be confused with causation."
The researchers also found that pupil size seemed to decrease with age. Older people had more constricted pupils but when the scientists standardized for age, the pupil-size-to-intelligence connection still remained.
Why are pupils linked to intelligence?
The connection between pupil size and IQ likely resides within the brain. Pupil size has been previously connected to the locus coeruleus, a part of the brain that's responsible for synthesizing the hormone and neurotransmitter norepinephrine (noradrenaline), which mobilizes the brain and body for action. Activity in the locus coeruleus affects our perception, attention, memory, and learning processes.
As the authors explain, this region of the brain "also helps maintain a healthy organization of brain activity so that distant brain regions can work together to accomplish challenging tasks and goals." Because it is so important, loss of function in the locus coeruleus has been linked to conditions like Alzheimer's disease, Parkinson's, clinical depression, and attention deficit hyperactivity disorder (ADHD).
The researchers hypothesize that people who have larger pupils while in a restful state, like staring at a blank computer screen, have "greater regulation of activity by the locus coeruleus." This leads to better cognitive performance. More research is necessary, however, to truly understand why having larger pupils is related to higher intelligence.
In an email to Big Think, Tsukahara shared, "If I had to speculate, I would say that it is people with greater fluid intelligence that develop larger pupils, but again at this point we only have correlational data."
Do other scientists believe this?
As the scientists point out in the beginning of their paper, their conclusions are controversial and, so far, other researchers haven't been able to duplicate their results. The research team addresses this criticism by explaining that other studies had methodological issues and examined only memory capacity but not fluid intelligence, which is what they measured.
A new study makes a surprising finding on the intelligence of psychopaths, often portrayed as evil geniuses in popular culture.
We tend to think of psychopaths as dangerous, antisocial, lacking in key human emotions like empathy or remorse. Psychopaths can be obsessed evil tyrants like Hitler or cunning and monstrous like the fictional Hannibal Lecter. Now a new study casts a surprising look at psychopaths, finding that whatever qualities they might have, high intelligence is not one of them. In fact, psychopaths were found to be less intelligent than average people.
Scientifically, to be classified as having the personality disorder of psychopathy, a person would need to achieve a corresponding score on a test of psychopathic traits like aggression, inflated sense of self-importance and dishonesty. Around 1 percent of the population would fall into this category.
"Not all psychopaths will break the law or hurt someone, but the odds of them doing so are higher," explained Brian Boutwell of St. Louis University in Missouri, who led the study.
One reason that spurred his research was the prevalence of the popular culture version of a psychopath, referred by psychologists as the “Hannibal Lecter myth." But that kind of Hollywoodized psychopath did not sit well with observed facts.
"Psychopaths are impulsive, have run-ins with the law and often get themselves hurt," said Boutwell. "That led me to think they're not overly intelligent."
Boutwell and his team conducted a meta-analysis of 187 previous studies on the relationship between psychopathy and intelligence, involving over 9,000 participants, some in prison and others in successful careers. The researchers found that psychopaths scored lower on intelligence tests. A surprising result, according to Boutwell.
"The results of the current meta-analysis produced a small, but significant effect size suggesting that individuals who score higher on measures of psychopathic traits tend to score lower on measures of IQ," the researchers wrote in the paper.
The researchers hope that their finding will contribute to our understanding psychopathy, currently an untreatable condition.
"Psychopathy isn't amenable to psychotherapies," pointed out Boutwell. "As we better understand psychopathy, we should be better able to develop treatment and rehabilitation for psychopaths."
Further research might also change how psychopaths are treated by the criminal justice system.
"If they have low intelligence, you could say that they are likely to offend again, or you could say that if they have cognitive difficulties, a lengthier prison sentence is not going to help them," said Boutwell. "You could make the argument in either direction."
Cover photo: Anthony Hopkins playing Hannibal Lecter. © 1991 - MGM
The IQ test is the most widely known measure of intelligence, but are the 'twice exceptional' and other gifted members of society slipping between the cracks?
Most of us know about the IQ test, whether you’ve taken one, read about it, or seen that episode of Seinfeld, it’s part of the lexicon when we talk about intelligence.
Conversely, here’s a less common term: ‘twice exceptional’, which is often abbreviated to 2e. This refers to those who have some form of disability but are also intellectually gifted (contrary to quick-fire biases, the two aren’t mutually exclusive). It’s this group – and people all across the intelligence and creativity spectrum – that misses out when aptitude is measured by what experts like Scott Barry Kaufman consider to be a fairly narrow test.
The IQ test was developed in the early 20th century, spring-boarding off the work of French psychologist Alfred Binet. It involves a series of standardized tests that measure a person’s mental age score, which is divided by their chronological age, and that fraction is then multiplied by 100 to obtain the IQ score. But the test has evolved over the 100 years since its inception, and even Binet’s work, which is often thought of as seminal, points to methods that he borrowed from other scholars. This mish-mash of tests has fluctuated over the years to reflect the values of the era, dropping tests that are seen as bad and retaining the ones that are considered good measures of intelligence.
But it has plenty of shapeshifting still to do, according to Kaufman. Intelligence takes many forms, and the IQ test doesn’t capture the full complexity of the human mind. Billionaire business magnate Richard Branson is an excellent example: "I was dyslexic, I had no understanding of schoolwork whatsoever. I certainly would have failed IQ tests. And it was one of the reasons I left school when I was 15 years old."
The IQ test doesn’t measure for factors like creativity, emotional sensitivity, real-world rationality, social intelligence and skills-based acumen. There are many ways to be gifted, and those who are twice exceptional or intellectually advanced outside of the normal parameters, can miss out on the developmental attention needed to cultivate their intellect to its full potential. Kaufman suggests retaining components of the IQ test to identify where people do well and spot intelligence patterns, but to also utilize new methodologies, and solicit parent and teacher readings as they are in a position to observe intelligence indicators day by day, such as deep sensitivity, questioning assumptions, or signs that a child is bored with their work. The more you can triangulate information from different sources, the better the measure of true intelligence will be.
If you’re now itching to know how you would perform on an IQ test, you can take one here, but don’t be too buoyed or disheartened by the results – intelligence is a sprawling entity that scientists are still mapping, and the IQ test is a well-worn but ultimately narrow path to tread.
Scott Barry Kaufman's book is Wired to Create: Unraveling the Mysteries of the Creative Mind.
The smartest humans in history are ranked.
Making a list of the smartest people who ever lived may not be a smart thing to do. After all, intelligence can be measured in a variety of different ways. Some believe in IQ tests, others place more stock in emotional intelligence. There's also something to be said about having accomplishments. Being intelligent is not the same as using that intelligence to create something that no one else can, to somehow advance humanity, to be smarter than everyone.
Many smart people do not live up to their potential. It is also true that prejudices and lack of opportunities have surely prevented some brilliant people from reaching their full potential and being recognized. Still, for the sake of argument, we will use all criteria at our disposal to come up with a list of the brightest humans.
Note: while IQ testing was developed in the early 1900s, there have been subsequent studies that estimated IQs of geniuses of the past. Anything above 140 is generally considered near genius-level.
24. William Siddis (1898-1944) was an American child prodigy, whose IQ was reportedly between 250-300, perhaps the highest ever. He had outstanding abilities in math, entered Harvard at age 11, and claimed to know 40 languages. An MIT professor predicted the young Siddis would become the greatest mathematician of the 20th century. William crashed and burned as an adult, however, holding menial jobs and getting in trouble with the law, never finding an avenue to live up to the expectations.
William Sidis. 1914.
23. Judit Polgar (b. 1976) is a Hungarian chess grandmaster, widely regarded as the strongest female chess player of all time. She broke Chess World Champion Bobby Fischer's record to become grandmaster at age 15. Her IQ is recorded as 170.
The youngest international chess grand master, 17-year-old Judit Polgar (L) writes down her first move 16 February, 1993 in her last match with Russian born chess champion Boris Spassky (R) in Budapest. (Photo credit: ATTILA KISBENEDEK/AFP/Getty Images)
22. Philip Emeagwali (b. 1954) is a Nigerian inventor and scientist, reportedly with an IQ of 190, voted as the “greatest African scientist of all time". Although this claim is controversial, his math work is often credited as being instrumental in the creation of the internet.
Philip Emeagwali with Exxon-Mobil partial differential equations for petroleum reservoir simulations across an internet powered by 65,536 computers. 2013. ©Photo: emeagwali.com
21. Terence Tao (b. 1975), Chinese, born in Australia, is a former a child prodigy whose IQ scores range from 220-230, some of the highest ever recorded. He is currently a Professor of Mathematics at UCLA.
Photo courtesy of the John D. and Catherine T. MacArthur Foundation
20. Cleopatra (68-30 B.C.) was the last pharaoh of Ptolemaic Egypt, ruling the country for almost thirty years. She was fluent in five languages and had an IQ of around 180. Cleopatra was also known for relationships with Julius Caesar and Marc Anthony.
Painting of Cleopatra by John William Waterhouse. 1888.
19. Srinivasa Ramanujan (1887-1920) was an Indian mathematician, who made great contributions in such areas as number theory, continued fractions, and infinite series, despite not having any formal education in math. His estimated IQ was 185.
Srinivasa Ramanujan. 1920.
18. Garry Kasparov (b. 1963), Armenian-Jewish, is regarded by many as the greatest chess player of all time, with an IQ reportedly in the 190s. He was the world's number one player for nearly two decades, winning the world championship when was only 22.
Chess legend Garry Kasparov plays chess with his Russian peer Anatoli Karpov (unseen) at the Arts Palau in Valencia on September 24, 2009, 25 years after their epic world championship duel. (Photo by JOSE JORDAN/AFP/Getty Images)
17. Aryabhata (476—55) was probably the earliest Indian mathematician and astronomer. He is known for approximating the value of pi and developed the knowledge and use of zero.
A statue of Aryabhata in Pune, India. 2006.
16. Voltaire (1694 – 1778) was a leading figure of the French Enlightenment. With an IQ of 190 to 200, he was a notoriously witty writer, historian and philosopher. "Voltaire" was actually his pen name as he was born François-Marie Arouet.
Source - Hulton Archive/Getty Images.
15. Hypatia (b.350-70, d. 415) was a Greek astronomer, philosopher and mathematician, who lived in Egypt and later the Eastern Roman Empire. She was the first female mathematician that we know of, with an estimated IQ of 170-190. She was accused of witchcraft and brutally murdered by a group of Christian fanatics.
Actress Mary Aynderson in a scene from the play, 'Hypatia'. circa 1900: (Photo by Hulton Archive/Getty Images)
14. Johann Goethe (1749-1832) was a German polymath, with notable achievements in science and considered to have been one of the greatest talents in Western literature, penning the classic “Faust". His projected IQ was 213.
Johann Wolfgang Von Goethe. circa 1790. Source - Hulton Archive/Getty Images.
13. Avicenna aka Ibn Sina (980 – 1037) was a Persian polymath who is regarded as one of the most important thinkers of the Islamic Golden Age. He wrote on philosophy, medicine, astronomy, alchemy, logic, math, physics, psychology and other subjects. He is particularly known for his work on Aristotelian philosophy and his medical books (like “The Canon of Medicine"), which became standard at Medieval universities.
Drawing of Avicenna from 1271.
12. Galileo Galilei (1564-1642) was one of the seminal scientific heroes of all times, making significant contributions in a variety of areas, from astronomy to physics to math and philosophy. The Italian's championing of heliocentrism, which saw Earth revolving around the sun got him branded as a heretic by the Roman Inquisition. His IQ range: 180-200.
Galileo Galilei, circa 1630. Source - Hulton Archive/Getty Images.
11. Gottfried Leibniz (1646-1716) was another German polymath - a philosopher and mathematician who is best known for inventing calculus. His philosophy work is noted for the conclusion that we lived in the best possible universe that God could have created. Leibniz's IQ estimates range from 182 to 205.
Gottfried Wilhelm von Leibniz, circa 1690. Source - Hulton Archive/Getty Images.
10. Nikola Tesla (1856-1943) was a Serbian-born inventor and futurist, known for AC electricity, Tesla coil, wireless transmission of energy, the “death" ray, as well as predicting the smartphone, drones and other technologies. Estimated IQ - 195.
9. Satyendra Nath Bose (1894-1974) was a Bengali Indian physicist, whose brilliant work on quantum mechanics with Albert Einstein resulted in Bose-Einstein statistics. Bosons, a class of particles, are named after him.
8. Marie Curie (1867-1934) was a Polish physicist and chemist. She was the first woman to win a Nobel Prize (in fact, winning it twice). She developed the theory of radioactivity (coining that term) and discovered two elements (polonium and radium). Her estimated IQ was 180-200.
Marie Curie in her laboratory. 1910. (Photo by Hulton Archive/Getty Images)
7. Confucius (551 B.C. - 479 B.C.) was a highly influential Chinese philosopher and teacher, renowned for popular aphorisms. His moral and political teachings had a profound impact all across East Asia. Some recent scholars have argued that much of what we know about Confucius is a myth.
Chinese philosopher Confucius, or K'ung Fu-tzu, circa 500 BC. Source - Rischgitz/Getty Images.
6. Albert Einstein (1879-1955) was a German-Jewish theoretical physicist who, for most people, is an obvious candidate for such a list as this. Arguably the most famous scientist who ever lived, Einstein developed the general theory of relativity, received a 1921 Nobel Prize for physics and had a revolutionary impact on his field. His IQ was estimated to be somewhere between 160-190.
Albert Einstein. 1930. Photo by Keystone/Getty Images.
5. William Shakespeare (1564-1616) is widely seen as the greatest writer of the English language and one of the world's most popular and esteemed playwrights. With an approximate IQ of 210, Shakespeare wrote such constantly-performed classic plays as “Romeo and Juliet," “Hamlet" and “Macbeth".
A painting of William Shakespeare which is believed to be the only authentic image of Shakespeare made during his life. 1610. (Source - Oli Scarff/Getty Images)
3-4. Plato (427 - 347 BC) and Aristotle (384 - 322 BC) were both Greek philosophers, who also had a major scientific influence on the Middle Ages. Plato was a foundational figure of Western science, math and philosophy, writing a number of famous works like “Republic". Aristotle was actually a pupil of Plato's, being a part of Plato's Athenian Academy for over 20 years. Aristotle had a major influence on the development of Western philosophy and science, writing on physics, biology, metaphysics, logic, theater, esthetics and other topics. IQs of the Greek thinkers are projected to be at 180-190.
Greek philosopher Plato Aristocles with the philosopher and scientist Aristotle. Ca. 350 BC. Original Publication: From Raphael: School of Athens - Vatican Stanzae (Source - Picture Post/Getty Images)
2. Sir Isaac Newton (1642-1726) was an English physicist and mathematician, most famous for discovering gravity. One of the most celebrated and influential scientists of all time, Newton had an estimated IQ of 193. His book Philosophiæ Naturalis Principia Mathematica was the foundational text of classical mechanics and influenced scientific thought for over 300 hundred years.
English scientist and mathematician Sir Isaac Newton, creating a shaft of light, circa 1665. Original Artwork: Engraving by J A Houston, RSA Original Publication: Aldus Disc - People & Personalities - 1353 - 007 (Source - Hulton Archive/Getty Images)
1. Leonardo da Vinci (1452-1519) was an Italian Renaissance man, who excelled in a variety of fields, from science to painting and sculpture to inventions. His painting “Mona Lisa" is arguably the most famous art work in the world. The IQ of the man, who was perhaps the most diversely talented person ever, is estimated to have been around 200.
The Italian painter, sculptor, architect and engineer Leonardo da Vinci, circa 1510. Original Artwork: Engraving by J Posselwhite after an engraving by Raphael Morghen, (1758 - 1833), after a self-portrait by da Vinci. (Source - Hulton Archive/Getty Images)