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.
Being an intellectual is not really how it is depicted in popular culture.
- When you picture an intellectual, who do you see? Professor Zena Hitz says that somewhere along the way, the idea of what an intellectual is and does became distorted.
- "The real thing is something more extraordinary but also more available to us," Hitz adds, differentiating between an intellectual life constantly in pursuit of something else, and one that enjoys ordinary activities like reading and thinking.
- An example is young Albert Einstein, who spoke highly of his time working in a patent office and hatching "beautiful ideas" long before becoming a famous physicist.
We can't ask them, so scientists have devised an experiment.
- Humans have the capacity for conscious awareness of our visual world.
- While all sighted animals respond to visual stimuli, we don't know if any of them consciously take note of what they're seeing in the way that we do.
- Researchers from Yale have devised experiments that suggest that rhesus monkeys share this ability.
All day long, our brains are busy receiving sensory information: smells, sounds, sights, and so on. We absorb much of this without really thinking about it. However, every now and then something we see grabs our attention, maybe a stunning landscape or a beautiful sunset. We stop what we're doing and spend a moment taking it in. Are we the only animal that can stop and take conscious notice of what we see?
A study just published in the Proceedings of the National Academy of Sciences suggests that we're not. It appears that at least one other animal — the rhesus monkey, Macaca mulatta — shares our ability to pay deliberate attention to what it sees. The authors of the study infer this ability, paradoxically, from the manner in which the monkey deals with visual inputs it doesn't consciously notice.
Credit: Amanda Dalbjörn/Unsplash
It has been known for some time that even when visual stimuli escape our conscious attention, we respond to it subliminally, says Yale psychologist Laurie Santos, co-senior author of the paper along with Yale psychologist Steve Chang and Ran Hassin of Hebrew University. Even so, she says, "We tend to show different patterns of learning when presented with subliminal stimuli than we do for consciously experienced, or supraliminal stimuli." ("Supraliminal" describes visual stimuli that are consciously noted.)
The authors of the study set out to see if rhesus monkeys exhibited a similar "double disassociation" in the way they respond to supraliminal vs. subliminal visual stimuli.
Ask a monkey a question
Credit: Jamie Haughton/Unsplash
Obviously, research on animals is hampered by our inability to question critters. As a result, scientists need to be creative in designing experimental methods that allow them to draw conclusions based strictly on empirical observation.
"People have wondered for a long time whether animals experience the world the way we do, but it's been difficult to figure out a good way to test this question empirically," says first author of the study, Moshe Shay Ben-Haim, a postdoctoral fellow at Yale University.
The researchers came up with a series of experiments in which both humans and rhesus monkeys could observably demonstrate how they process subliminal and supraliminal visual stimuli.
In the experiments, participants were tasked with predicting the side of a computer screen on which a target image would appear depending on the position of a visual cue, a small star symbol, provided by the researchers.
When the researchers displayed the cue on one side of the screen long enough to ensure that it was noticed — that is, it was a supraliminal signal — both humans and monkeys learned to look for the target image on the opposite side of the screen.
On the other hand, when the star flashed on the screen only very briefly, both humans and monkeys consistently looked to the side on which this subliminal signal had appeared, anticipating the target image's appearance there.
In the first case, the subjects learned the significance of the cue's position. In the second, their response simply mirrored the subliminal cue. This, say the authors, demonstrates the different ways in which humans — and monkeys apparently — react to visual stimuli that are consciously noticed or not.
Ben-Haim summarizes the authors' interpretation of the experiment:
"These results show that at least one non-human animal exhibits both non-conscious perception as well as human-like conscious visual awareness. We now have a new non-verbal method for assessing whether other non-human creatures experience visual awareness in the same way as humans."
Digitized logbooks from the 1800s reveal a steep decline in strike rate for whalers.
Until someone works out a way to communicate with them, we can't really know how smart whales are. We do know they have the largest brains of any animals on the planet—of course, big is a thing they do really well altogether—and that their brains have more cortical convolutions than any other creature, including humans. There are indications that they're quite intelligent.
If that's so, however, why did 19th-century whalers in the North Pacific find it so easy to drive them to the edge of extinction? Didn't they see what was happening? New research published by the Royal Society in the U.K. apparently has an answer to that question, and it is "yes." An analysis of newly digitized whalers' log books finds that whalers' ability to harpoon sperm whales dropped precipitously after initial successes.
One possible explanation for the falloff would be that whalers' competence somehow degraded over time, but that doesn't seem especially logical. A more likely interpretation is that whales warned each other and modified their behavior to avoid the ships. If this is so, it suggests several thrilling things about the animals. First, they apparently shared information about the new predators, and second, they developed an effective evasive strategy.
A good look at mariners’ records
Credit: Aris Suwanmalee/Adobe Stock
The paper was written by cetacean experts Hal Whitehead of Dalhousie University in Halifax, Nova Scotia and Luke Rendell of University of St. Andrews in Scotland, along with data scientist Tim. D. Smith. Whitehead and Rendell are co-authors of "The Cultural Lives of Whales and Dolphins."
The researchers were working from the logbooks of American whalers operating between 10° and 50° in the North Pacific Ocean in the 19th century. The daily logs listed a ship's noon position, the number of sperm whales sighted, and how many whales were harpooned ("struck") or processed ("tried"). These records allowed the researchers to identify the date on which first contact with local whales occurred. From there, they were able to calculate the rate at which whales were encountered over the subsequent years.
The researchers found that about 2.4 years after first contact, whalers' strike rate fell by 58 percent.
At first, it seems the whales didn't quite know what to do about the whalers and responded to them similarly to the manner in which they defend themselves against the only predator they'd known up to that point: orcas. They formed defensive circles, their powerful tails pointed out to fend off their attackers. Unfortunately, this provided no defense against harpoons and likely made whaler's jobs easier by gathering groups of whales together where they could be easily killed.
Soon however, the leviathan strategy shifted and whales took to swimming upwind away from whalers' ships, an effective evasive maneuver that kept them ahead of the wind-driven boats. As White tells The Guardian, "This was cultural evolution, much too fast for genetic evolution."
Whale social learning and strategy
Spectrogram of a humpback whale song
Credit: Spyrogumas/Wikimedia Commons
While there remains debate over whether whale communities exhibit characteristics we'd recognize as culture, examples of what seems to be social learning support the idea that it does exist.
Whales are known to communicate with each other over large distances through their haunting—and mysterious to us—songs. These songs provide some hard-to-argue-with evidence for social leaning among whales: They evolve over time, and as they change, those changes are reflected by entire local whale populations. "We don't have to do anything but observe it to know that there's no explanation other than learning from others that can account for this," wrote Whitehead and Rendell to NPR in 2015.
Rendell wrote in Science in 2013 about what seems to be an innovation that was shared among whales: the spread of a particular type of feeding, "lobtailing," that seems to have spread from one humpback whale in 1980 to hundreds in a wider area over the next few decades.
There are also examples of cetaceans clearly using strategy, such as the manner in which orcas hunt together for Weddell seals, described by NOAA scientist Bob Pitman. The seals attempt to evade the orcas by remaining out of the water on ice floes. The orcas synchronize their flukes to create waves that either knock a seal off of a floe, or break the ice apart. Once the seal is in the water, the orcas blow bubbles under the water and apparently using their tails to create enough turbulence that the seal finds it harder to get back on the ice. If it does get out to safety, the orcas do it all over again until, according to Pitman, by about the fourth attempt, they usually have their prey, which they share.
And then there's the whales' evasive tactics for dealing with 19th-century whaling ships.
Back to the present and future
Unfortunately, modern vessels , equipment, and strategies were not as easy to evade, and whale populations were severely depleted in the 20 century. And while that threat is hopefully diminishing, modern fishing tactics such a long-line fishing that hooks whales, the intrusion of human noise in the oceans, plastics and other floating waste, and climate change means that today's seas are just as challenging as ever to whales. Maybe moreso. And nobody can outswim climate change.
Labeling thinkers like Albert Einstein and Steve Jobs as "other" may be stifling humanity's creative potential.
- Revolutionary ideas and culture-shifting inventions are often credited to specific individuals, but how often do these "geniuses" actually operate in creative silos?
- Tim Sanders, former chief strategy officer at Yahoo, argues that there are three myths getting in the way of innovative ideas and productive collaborations: the myths of the expert, the eureka moment, and the "lone inventor."
- More than an innate quality reserved for an elite group, neuroscientist Heather Berlin and neurobiologist Joy Hirsch explain how creativity looks in the brain, and how given opportunity, resources, and attitude, we can all be like Bach, Beethoven, and Steve Jobs.