By Rivka Galchen During his first year as a professor of computer science at the University of California, Berkeley, Ren Ng was hurriedly putting together a survey course on computer graphics. In the syllabus he had inherited, a full week had been devoted to the subject of color. Ng thought that was a bit much. “I’m, like, Come on. It’s R.G.B.,” he said, referring to the red, green, and blue subpixels that constitute anything you see on a screen—your cluttered desktop, a Sahara-desert screen saver, the stream of the Netherlands-Japan World Cup game. Ng started gathering slides that would cover the wavelengths of light, the biology of the human eye—the basics—“Blah, blah, blah,” he said. A colleague shared a slide that he thought might be useful. It included a minutely detailed photograph of a patch of retina, seen through a microscope, which was attributed to Austin Roorda, a professor of vision science and optometry just across campus. Roorda’s lab had helped develop technology that could map the layout of individual cone cells—those primarily responsible for perceiving color—and that, furthermore, could target a single cone cell with light. Eyes are constantly moving; cone cells are extremely small; how color is translated from the millions of cone cells to the mind remains pretty mysterious; this was awesome work. Roorda’s lab was using the new technology to explore eye disease and the mechanics of how we see. Ng had his own notion, though: he wondered if it could be used to see a color that had never been seen before. To understand what Ng had in mind requires knowing a bit of the blah, blah, blah of color vision. We humans experience three primary colors not because the world is fundamentally composed of three colors but because our retinas typically have three kinds of color-perceiving cone cells. L cone cells respond to the relatively longer wavelengths of visible light, M cone cells to the medium wavelengths, and S cone cells to the shorter ones. In effect, this means that L cells respond most strongly to red light, M to green, and S to blue. But when you look at your hand—or a blade of grass, or a clear blue sky, or a fire truck—it is always some mixture of L, M, and S cone cells that are being stimulated. Ng’s idea was to use the Roorda lab’s technology to stimulate an array of cone cells in a manner that would never occur naturally. Ng said, “I e-mailed him, basically, What would happen if you stimulated only the M cells? Would that be like the greenest green, or what?” Roorda did not reply. © 2026 Condé Nast.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 30354 - Posted: 08.01.2026

By Emily Laber-Warren When sunlight hits an octopus, it can trigger a swift color change and instant camouflage, thanks to light-sensitive molecules embedded in the creature’s skin. When sunlight falls on a bird’s skull, similar compounds deep in the animal’s brain register changes in day length and help drive decisions on when to mate or migrate. Photosensitive proteins called opsins that respond instantly to sunlight can be found within and outside the eye in nearly every animal, and they govern not only vision but also a range of behaviors. Until about a quarter-century ago, though, the scientific consensus was that in humans, the only role for opsins was to help us see. But a surge of research over the past couple of decades has increasingly revealed that, like honeybees, zebra fish, rodents and other creatures, we harbor opsins that aren’t involved in vision, both in our eyes and throughout our bodies. These molecules appear to play a broad role in human biology, affecting mood, metabolism, sleep, thinking and social behavior. Since life’s beginnings, organisms on this sunbaked planet have had to evolve ways to protect against ultraviolet light, which can damage DNA. But it shouldn’t be surprising that, as dangerous as sunlight can be, most animals also rely on it to regulate key aspects of physiology, including body temperature, navigation, growth and sexual development. Across the animal kingdom, researchers are discovering that light-sensing opsins are involved in an array of biological processes beyond vision. These include camouflage; sensing seasonal changes via lengthening or shortening day lengths; synchronizing with the 24-hour cycle — as well as mood, healing and more.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 10: Biological Rhythms and Sleep
Link ID: 30347 - Posted: 07.29.2026

By K. R. Callaway You (probably) won’t find a monkey in a geometry class, but it looks like our fellow primates can swing the basics. Just like people, monkeys seem to grasp the abstract qualities of geometric shapes, such as whether they are symmetrical, have parallel sides or contain right angles, according to a new study published on Monday in Proceedings of the National Academy of Sciences. This ability allows the monkeys — and us — to understand when two shapes are the same, even when they’ve been rotated or resized. This finding challenges a long-held notion that humans’ geometric abilities are part of what makes our brains one of a kind. “Our hypothesis was that humans are not that unique,” in possessing this mathematical understanding, said Jialin Li, a cognitive neuroscientist at Carnegie Mellon University and the lead author of the study. In their experiment, Ms. Li and her colleagues decided to give monkeys (a total of eight rhesus macaques and olive baboons), preschoolers and adult humans with different education levels the same geometric task. That way, if humans truly had an innate advantage, it would show up when comparing the young children and the monkeys. And if the advantage was learned, it might show up when comparing the humans who had different levels of schooling. It was a challenge to find a task simple enough that even preschool-aged children and monkeys could reasonably complete it, but the team eventually decided to have all the study participants do a matching task. All were shown a shape with a specific size and geometric form on a screen. Then they were asked to pick that same shape out of a group of others. “By manipulating the similarity of the shapes, we were able to look at what kinds of rules they’re using,” said Jessica Cantlon, a cognitive neuroscientist at Carnegie Mellon University whose lab conducted the study. © 2026 The New York Times Company

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 14: Attention and Higher Cognition
Link ID: 30337 - Posted: 07.22.2026

By Claudia López Lloreda Neurons in the visual cortex decode an object’s orientation—horizontal, vertical or anything in between—using information from non-orientation-tuned neurons in the thalamus, according to David Hubel and Torsten Wiesel’s Nobel Prize-winning work in cats in the 1950s and ’60s. In other species, though, the process remained unclear. Thalamic neurons in mice, for example, show orientation selectivity, subsequent studies suggested. New mouse findings—realized by imaging individual synapses on cortical neurons and distinguishing which inputs come from the thalamus versus the neighboring cortex during visual processing—help resolve the discrepancy. Signals coming into the primary visual cortex, or V1, from the thalamus are not orientation tuned, but those from other parts of the cortex are, confirming that orientation tuning occurs in the visual cortex, the new study reveals. This study is the first “to get a map of thalamic receptive field location at the level of seeing almost all the spines that receive thalamic input,” says Jose Manuel Alonso, professor of biological and vision sciences at the State University of New York College of Optometry, who was not involved with the work. “This is unbelievably beautiful.” What’s more, the Hubel and Wiesel model of orientation selectivity “is preserved through evolution,” Alonso adds. “In the mouse, this pathway from the thalamus to the V1 is really organized as the Hubel and Wiesel suggested it should be,” says Anton Arkhipov, investigator at the Allen Institute, who was not involved with the study. © 2026 Simons Foundation

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 3: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 30262 - Posted: 05.30.2026

By Yasemin Saplakoglu When an optometrist shines a bright light into your eyes, a vast, branching tree sprouts in your field of vision. This is the shadow of blood vessels. Though we normally can’t perceive them, these vessels always occlude a portion of what we see, and for an important reason. They power the retina, a thin layer of nerve tissue in the back of the eye that communicates light signals to the brain. The retina is one of the body’s most energetically expensive tissues. Built from complex networks of sometimes more than 100 different types of neurons, retinal tissue consumes two to three times more energy than the same mass of typical brain tissue. That’s why most vertebrate retinas, including our own, are furrowed with dense, branching networks of blood vessels: to deliver oxygen and other ingredients for producing energy. But there’s a significant exception to this rule. Birds have retinas that mostly lack blood vessels. This may seem especially strange given birds’ exceptional vision. The bird retina is “one of the most metabolically active tissues in the animal kingdom, yet it worked with no apparent blood perfusion,” said Christian Damsgaard (opens a new tab), an evolutionary physiologist at Aarhus University. “It was a complete paradox.” For centuries this has puzzled scientists, who figured that the bird retina must obtain oxygen through a unique, undiscovered process. Damsgaard is the lead author of a study, published in the journal Nature (opens a new tab) in January 2026, that showed for the first time that bird retinas don’t have some unusual adaptation for acquiring oxygen — they survive without it entirely. Instead, to bring energy to the tissue, they use a process called anaerobic glycolysis that is significantly less efficient than oxygen-powered metabolism but gets the job done. © 2026.Simons Foundation

Related chapters from BN: Chapter 6: Evolution of the Brain and Behavior; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 30247 - Posted: 05.16.2026

Ian Sample Science editor A married couple who met over a dissected brain and went on to create the first approved gene therapy for blindness have been awarded one of the most lucrative prizes in science. Molecular biologist Jean Bennett and ophthalmologist Albert Maguire share the $3m (£2.2m) Breakthrough prize for life sciences with physician Katherine High for the 25-year-long project, during which the couple adopted a pair of dogs they had treated for blindness. The therapy, named Luxturna, was approved in the US in 2017 and has transformed the lives of people born with Leber congenital amaurosis (LCA), a genetic disorder that typically causes total blindness by early adulthood. Proof that the therapy worked came in a clinical trial in which one patient described seeing their child’s face for the first time, the fine grain in wooden furniture and branches waving in the wind. Other patients reported similar profound improvements. Nine slices of bread toasted and burned to different degrees, from white to blackened. “I was overwhelmed,” said Bennett, who is now retired from the University of Pennsylvania. “It was one of the most miraculous eureka moments you can imagine.” Bennett said it was a “tremendously exciting time” for scientific and medical research, but warned that the US administration’s attacks on science could “cause damage for generations to come”, leading her to fear a brain drain that the country would struggle to recover from. “Agendas have become politicised, government agencies that support basic and applied research have been undermined, knowledgable advisers and experts have been dismissed or have fled and revised guidelines contradict decades of rigorous research,” she said. © 2026 Guardian News & Media Limited

Related chapters from BN: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 30212 - Posted: 04.22.2026

Jon Hamilton It's often called the mind's eye. "I can look at an object in the world around me, but I can also close my eyes and imagine the object," says Varun Wadia, a brain scientist at Cedars-Sinai Medical Center and the California Institute of Technology. That sort of visual imagination, Wadia says, is what allows most people to conjure the face of a loved one or navigate to work using a mental map. For 'time cells' in the brain, what matters is what happens in the moment Shots - Health News For 'time cells' in the brain, what matters is what happens in the moment But its neural underpinnings were a mystery until Wadia and a team reported in the journal Science that imagined and perceived objects appear to activate the same neurons and use the same neural code. "This has not been demonstrated before at the neural level," says Kalanit Grill-Spector, a psychology professor at Stanford University's Wu Tsai Neurosciences Institute, who was not involved in the research. With these insights, she says, scientists are one step closer to building computer models that can simulate vision as well as vision disorders like macular degeneration. These models, in turn, could help researchers develop prosthetic devices to restore sight. The research also helps explain how the brain uses imagination to augment visual information, says Thomas Naselaris, a neuroscientist at the University of Minnesota. © 2026 npr

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 14: Attention and Higher Cognition
Link ID: 30210 - Posted: 04.22.2026

Ian Sample Science editor Scientists have reconstructed short movies from the brain activity of mice that watched videos for a project that aspires to lift the veil on how animals perceive the world. The brief movie clips are grainy and pixellated, but provide a glimpse of how mice processed footage that featured people taking part in various sports from gymnastics to horse riding and wrestling. The work is in its infancy, but as technology advances, scientists hope to eavesdrop on a richer suite of animal perceptions and ultimately gain fresh insights into their experiences and how brains more broadly respond to their surroundings. “The nice thing with humans is you can just ask someone, what did you dream about? What did you see? What are you hallucinating?” said Dr Joel Bauer at the Sainsbury Wellcome Centre at University College London. “But we don’t have that access with animals in the same way.” Central to the work was an artificial intelligence program that won a recent scientific competition to predict how electrical activity in the visual cortex of the mouse brain changes depending on what the animals are seeing. The visual cortex receives raw input from the retina and turns it into a coherent view of the world. To reconstruct what mice were watching, the scientists first used an infrared laser to record how neurons were firing in the visual cortex as the rodents watched 10-second-long movie clips. They then fed blank video data into the AI program and steadily altered the imagery until the AI predicted the same patterns of brain activity as those seen in the mice. Details are published in the journal eLife. Mice have poor eyesight compared with humans, so the reconstructed videos may never be as clear as the originals. But at a rough guess, Bauer suspects scientists could make the footage about seven times sharper than it is at present. © 2026 Guardian News & Media Limited

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 2: Functional Neuroanatomy: The Cells and Structure of the Nervous System
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 2: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 30157 - Posted: 03.11.2026

By Sachin Rawat One can spend hours looking at a calm sunset or a clear night sky. These scenes are not only effortless on the eyes — they may also be easy on the brain. People tend to like visual stimuli that require little cognitive effort to process, researchers report in the December PNAS Nexus. The brain is the most energy-guzzling organ in the body, and visual processing alone accounts for nearly half of its energy use. Researchers have long studied how the visual system conserves energy. But the new study addresses the question from a different perspective. “Not only is the visual system optimized for efficiency, but we might have aesthetic preferences for stimuli that are efficient to process,” says Mick Bonner, a neuroscientist at Johns Hopkins University who was not involved in the study. Neuroscientist Dirk Bernhardt-Walther of the University of Toronto and his colleagues suspected that such preferences could have evolved as cognitive shortcuts, helping organisms avoid excessive effort as they navigate their environment. To probe the energy consumed in visual processing, the researchers turned to an existing functional MRI dataset, in which four individuals viewed 5,000 images while their brain activity was monitored. Measurements of oxygen consumption in different parts of the brain provided an indicator of metabolic activity. The team also ran these images through an artificial neural network trained on object and scene recognition, using the proportion of activated “neurons” as a proxy for metabolic expense. The researchers then compared these metabolic cost estimates — both human and artificial — to the images’ aesthetic ratings, gathered from more than 1,000 online survey respondents who scored each picture on a five-point scale. In both cases, the metabolic effort required to process the images was inversely proportional to their aesthetic ratings. © Society for Science & the Public 2000–2026.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 11: Emotions, Aggression, and Stress
Link ID: 30072 - Posted: 01.10.2026

By Kaia Glickman Anyone with a computer has been asked to “select every image containing a traffic light” or “type the letters shown below” to prove that they are human. While these log-in hurdles — called reCAPTCHA tests — may prompt some head-scratching (does the corner of that red light count?), they reflect that vision is considered a clear metric for differentiating computers from humans. But computers are catching up. The quest to create computers that can “see” has made huge progress in recent years. Fifteen years ago, computers could correctly identify what an image contains about 60 percent of the time. Now, it’s common to see success rates near 90 percent. But many computer systems still fail some of the simplest vision tests — thus reCAPTCHA’s continued usefulness. Digital artwork, one in a series displayed at CERN in Geneva. The foreground shows a particle collision event which is a possible candidate for a decay of the Higgs-like particle to a final state. The background depicts selected pages from articles published by the CMS collaboration at the LHC. Newer approaches aim to more closely resemble the human visual system by training computers to see images as they are — made up of actual objects — rather than as just a collection of pixels. These efforts are already yielding success, for example in helping develop robots that can “see” and grab objects. Computer vision models employ what are called visual neural networks. These networks use interconnected units called artificial neurons that, akin to in the brain, forge connections with each other as the system learns. Typically, these networks are trained on a set of images with descriptions, and eventually they can correctly guess what is in a new image they haven’t encountered before.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 29996 - Posted: 11.01.2025

By Gina Kolata For the first time, researchers restored some vision to people with a common type of eye disease by using a prosthetic retinal implant. If approved for broader use in the future, the treatment could improve the lives of an estimated one million, mostly older, people in the United States who lose their vision to the condition. The patients’ blindness occurs when cells in the center of the retina start to die, what is known as geographic atrophy resulting from age-related macular degeneration. Without these cells, patients see a big black spot in the center of their vision, with a thin border of sight around it. Although their peripheral vision is preserved, people with this form of advanced macular degeneration cannot read, have difficulty recognizing faces or forms and may have trouble navigating their surroundings. In a study published Monday in The New England Journal of Medicine, vision in 27 out of 32 participants improved so much that they could read with their artificial retinas. The vision that is restored is not normal: It’s black and white, blurry, and the field of view is small. But after getting the retinal implant, patients who could barely see gained on average five lines on a standard eye chart. The implant gets signals from glasses and a camera that projects infrared images to the artificial retina. The camera has a zoom feature that can magnify images like letters, allowing people to read, albeit slowly because with the zoom they don’t see many letters at a time. “This is at the forefront of science,” said Dr. Demetrios Vavvas, director of the retina service at Massachusetts Eye and Ear, a specialty hospital in Boston. He was not involved in the study and emphasized that the implant was not a cure for macular degeneration. But he called it the dawn of a new technology that he predicted will significantly advance. The treatment is only for people with a loss of retinal photoreceptors, so it would not work for other forms of blindness. The study participants had an average age of 79 and had been told that once vision was lost, it was gone forever. © 2025 The New York Times Company

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 3: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 3: The Chemistry of Behavior: Neurotransmitters and Neuropharmacology
Link ID: 29981 - Posted: 10.22.2025

By Grace Lindsay Neuroscientists have spent decades characterizing the types of information represented in the visual system. In some of the earliest studies, scientists recorded neural activity in anesthetized animals passively viewing stimuli—a setup that led to some of the most famous findings in visual neuroscience, including the discovery of orientation tuning by David Hubel and Torsten Wiesel. But passive viewing, whether while awake or anesthetized, sidesteps one of the more intriguing questions for vision scientists: How does the rest of the brain use this visual information? Arguably, the main reason for painstakingly characterizing the information in the visual system is to understand how that information drives intelligent behavior. Connecting the dots between how visual neurons respond to incoming stimuli and how that information is “read out” by other brain regions has proven nontrivial. It is not clear that we have the necessary experimental and computational tools at present to fully characterize this process. To get a sense for what it might take, I asked 10 neuroscientists what experimental and conceptual methods they think we’re missing. Decoding is a common approach for understanding the information present in the visual system and how it might be used. But decoding on its own—training classifiers to read out prespecified information about a visual stimulus from neural activity patterns—cannot tell us how the brain uses information to perform a task. This is because the decoders we use for data analysis do not necessarily match the downstream processes implemented by neural circuits. Indeed, there are pieces of information that can reliably be read out from the visual system but aren’t accessible to participants during tasks. Primary visual cortex contains information about the ocular origin of a stimulus, for example, but participants are not able to accurately report this information. © 2025 Simons Foundation

Related chapters from BN: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 29970 - Posted: 10.15.2025

Asif Ghazanfar Picture someone washing their hands. The water running down the drain is a deep red. How you interpret this scene depends on its setting, and your history. If the person is in a gas station bathroom, and you just saw the latest true-crime series, these are the ablutions of a serial killer. If the person is at a kitchen sink, then perhaps they cut themselves while preparing a meal. If the person is in an art studio, you might find resonance with the struggle to get paint off your hands. If you are naive to crime story tropes, cooking or painting, you would have a different interpretation. If you are present, watching someone wash deep red off their hands into a sink, your response depends on even more variables. How we act in the world is also specific to our species; we all live in an ‘umwelt’, or self-centred world, in the words of the philosopher-biologist Jakob von Uexküll (1864-1944). It’s not as simple as just taking in all the sensory information and then making a decision. First, our particular eyes, ears, nose, tongue and skin already filter what we can see, hear, smell, taste and feel. We don’t take in everything. We don’t see ultraviolet light like a bird, we don’t hear infrasound like elephants and baleen whales do. Second, the size and shape of our bodies determine what possible actions we can take. Parkour athletes – those who run, vault, climb and jump in complex urban environments – are remarkable in their skills and daring, but sustain injuries that a cat doing the exact same thing would not. Every animal comes with a unique bag of tricks to exploit their environment; these tricks are also limitations under different conditions. Third, the world, our environment, changes. Seasons change, what animals can eat therefore also changes. If it’s the rainy season, grass will be abundant. The amount of grass determines who is around to eat it and therefore who is around to eat the grass-eaters. Ultimately, the challenge for each of us animals is how to act in this unstable world that we do not fully apprehend with our senses and our body’s limited degrees of freedom. There is a fourth constraint, one that isn’t typically recognised. Most of the time, our intuition tells us that what we are seeing (or hearing or feeling) is an accurate representation of what is out there, and that anyone else would see (or hear or feel) it the same way. But we all know that’s not true and yet are continually surprised by it. It is even more fundamental than that: you know that seemingly basic sensory information that we are able to take in with our eyes and ears? It’s inaccurate. How we perceive elementary colours, ‘red’ for example, always depends on the amount of light, surrounding colours and other factors. In low lighting, the deep red washing down the sink might appear black. A yellow sink will make it look more orange; a blue sink may make it look violet. © Aeon Media Group Ltd. 2012-2025.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 14: Attention and Higher Cognition
Link ID: 29961 - Posted: 10.08.2025

By Kenneth Chang After decades of brain research, scientists still aren’t sure whether most people see the same way, more or less — especially with colors. Is what I call red also red for you? Or could my red be your blue? Or maybe neon pink? If it were possible to project what I see directly into your mind, would the view be the same, or would it instead resemble a crazy-hued Andy Warhol painting? “That’s an age-old question, isn’t it?” said Andreas Bartels, a professor of visual neuroscience at the University of Tübingen in Germany. But scientists do have a good understanding of which parts of the brain handle vision. They have even figured out where various vision-processing tasks are performed, like recognizing what is moving, identifying colors and adjusting to different lighting conditions. Amazingly, it is even possible to deduce what you’re seeing by looking at an M.R.I. scan showing which parts of your brain are lighting up. “That comes out of the world of science fiction, or one would think, right?” Dr. Bartels said. “It’s amazing that this is possible, but this always has happened in individual brains.” That is, researchers pulled off this sleight of science with individuals. They would first show a subject lying in the M.R.I. machine a series of images, mapping out how that person’s brain responded. After that initial training, the researchers could randomly show one of the images and, based on just the brain activity, make a good guess at what the image was. In new research, Dr. Bartels and Michael Bannert, a postdoctoral researcher in Dr. Bartels’ laboratory, used that technique to provide a partial answer to the question of whether most of us have a shared sense of colors. They put 15 people, all with standard color vision, in an M.R.I. machine. The volunteers viewed expanding concentric rings that were red, green or yellow. © 2025 The New York Times Company

Related chapters from BN: Chapter 18: Attention and Higher Cognition; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 14: Attention and Higher Cognition; Chapter 7: Vision: From Eye to Brain
Link ID: 29925 - Posted: 09.10.2025

By Nora Bradford During her training in anthropology, Dorsa Amir, now at Duke University, became fascinated with the Müller-Lyer illusion. The illusion is simple: one long horizontal line is flanked by arrowheads on either side. Whether the arrowheads are pointing inward or outward dramatically changes the perceived length of the line—people tend to see it as longer when the arrowheads point in and as shorter when they point out. Graphic shows how the Müller-Lyer illusion makes two equal-length lines seem to have different lengths because of arrowlike tips pointing inward or outward. Most intriguingly, psychologists in the 1960s had apparently discovered something remarkable about the illusion: only European and American urbanites fell for the trick. The illusion worked less well, or didn’t work at all, on groups surveyed across Africa and the Philippines. The idea that this simple illusion supposedly only worked in some cultures but not others compelled Amir, who now studies how culture shapes the mind. “I always thought it was so cool, right, that this basic thing that you think is just so obvious is the type of thing that might vary across cultures,” Amir says. But this foundational research—and the hypothesis that arose to explain it, called the “carpentered-world” hypothesis—is now widely disputed, including by Amir herself. This has left researchers like her questioning what we can truly know about how culture shapes how we see the world. When researcher Marshall Segall and his colleagues conducted the cross-cultural experiment on the Müller-Lyer illusion in the 1960s, they came up with a hypothesis to explain the strange results: difference in building styles. The researchers theorized that the prevalence of carpentry features, such as rectangular spaces and right angles, trained the visual systems of people in more wealthy, industrialized cultures to perceive these angles in a way that make them more prone to the Müller-Lyer illusion. © 2025 SCIENTIFIC AMERICAN

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory and Learning
Link ID: 29899 - Posted: 08.23.2025

By Tina Hesman Saey A snail may hold the key to restoring vision for people with some eye diseases. Golden apple snails (Pomacea canaliculata) are freshwater snails from South America. Alice Accorsi became familiar with the species as a graduate student in Italy. “You could literally buy them in a pet store as snails that clean the bottom of the fish tanks,” she recalls. Turns out, the snails are among the most invasive species in the world. And that got Accorsi thinking: Why are they so resilient and able to thrive in new environments? She began studying the snails’ immune systems and has now found they are not the only parts of the animals able to bounce back from adversity. These snails can completely regrow a functional eye within months of having one amputated, Accorsi and colleagues report August 6 in Nature Communications. Side-by-side images of snail eyes. On the left is a normal, intact snail eye. On the right is an eye that has regrown two months after it was surgically removed. The eyes look similar. They are both round with a black spot in the middle. A snail’s eye was surgically removed, but it grew a new one. Two months after amputation the new eye (right) looks much like the uninjured one (left).Alice Accorsi Scientists have known for centuries that some snails can regrow their heads, and research has revealed other animals can regenerate bodies, tails or limbs. But this finding is exciting because apple snails have camera-like eyes similar to those of humans. Understanding how the snails re-create or repair their eyes might lead to therapies to heal people’s eye injuries or reverse diseases such as macular degeneration. Accorsi, now a developmental biologist at the University of California, Davis, used the molecular scissors called CRISPR/Cas9 to genetically disable certain key genes involved in eye development and established lineages of snails carrying those mutations. © Society for Science & the Public 2000–2025.

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 29879 - Posted: 08.06.2025

Emily Kwong A grayscale ballerina who appears to be moving. A human who can fit in a doll box. A black-and-white prism which appear to change shape when viewed from three different directions. Those are the top winners of the 2024 Best Illusion of the Year Contest, open to illusion makers around the world. The contest was co-created by neuroscientist and science writer Susana Martinez-Conde. After 20 years, Martinez-Conde is still amazed that novel illusions keep coming in — submitted by artists, magicians, vision scientists and illusion makers all over the world. "Illusions are fundamental to the way that we perceive the world — the way that, frankly, we exist as human beings. Illusions are a feature and not a bug," she told All illusions are perceptual experiences that do not match physical reality. Aristotle was one of the first to document an illusion in nature, the so-called "waterfall illusion," or motion aftereffect. When someone watches a moving stimulus, such as a river, a nearby stationary object, like a rock, may also appear to move. Other famous illusions include "Rotating Snakes," which Martinez-Conde has studied as part of her research into peripheral drift. As a scientist, Martinez-Conde sees as illusions as an opportunity to study how the human brain constructs perceptions of the world. "We can analyze the neurons and the brain circuits that support neural activity that matches perception, and those could be part of the neural basis of consciousness." Voting for the 2025 Best Illusion of the Year will take place next year. The online contest is run by the non-profit Neural Correlate Society. © 2025 npr

Related chapters from BN: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 29871 - Posted: 08.02.2025

By Katrina Miller Take a look at this video of a waiting room. Do you see anything strange? Perhaps you saw the rug disappear, or the couch pillows transform, or a few ceiling panels evaporate. Or maybe you didn’t. In fact, dozens of objects change in this video, which won second place in the Best Illusion of the Year Contest in 2021. Voting for the latest version of the contest opened on Monday. Illusions “are the phenomena in which the physical reality is divorced from perception,” said Stephen Macknik, a neuroscientist at SUNY Downstate Health Sciences University in Brooklyn. He runs the contest with his colleague and spouse, Susana Martinez-Conde. By studying the disconnect between perception and reality, scientists can better understand which brain regions and processes help us interpret the world around us. The illusion above highlights change blindness, the brain’s failure to notice shifts in the environment, especially when they occur gradually. To some extent, all sensory experience is illusory, Dr. Martinez-Conde asserts. “We are always constructing a simulation of reality,” she said. “We don’t have direct access to that reality. We live inside the simulation that we create.” She and Dr. Macknik have run the illusion contest since 2005. What began as a public outreach event at an academic conference has since blossomed into an annual competition open to anyone in the world. They initially worried that people would run out of illusions to submit. “But that actually never happened,” Dr. Martinez-Conde said. “What ended up happening instead is that people started developing illusions, actually, with an eye to competing in the contest.” © 2025 The New York Times Company

Related chapters from BN: Chapter 10: Vision: From Eye to Brain; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 14: Attention and Higher Cognition
Link ID: 29843 - Posted: 06.28.2025

By Nala Rogers Coffer illusion What do you see when you stare at this grid of line segments: a series of rectangles, or a series of circles? The way you perceive this optical illusion, known as the Coffer illusion, may tie back to the visual environment that surrounds you, a recent preprint suggests.Anthony Norcia/Smith-Kettlewell Eye Research Institute Himba people from rural Namibia can see right through optical illusions that trick people from the United States and United Kingdom. Even when there’s no “right” or “wrong” way to interpret an image, what Himba people see is often vastly different from what people see in industrialized societies, a new preprint suggests. That could mean people’s vision is fundamentally shaped by the environments they’re raised in—an old but controversial idea that runs counter to the way human perception is often studied. For example, when presented with a grid of line segments that can be seen as either rectangles or circles—an optical illusion known as the Coffer illusion—people from the U.S. and U.K. almost always see rectangles first, and they often struggle to see circles. The researchers suspect this is because they are surrounded by rectangular architecture, an idea known as the carpentered world hypothesis. In contrast, the traditional villages of Himba people are composed of round huts surrounding a circular livestock corral. People from these villages almost always see circles first, and about half don’t see rectangles even when prompted. “I’m surprised that you can’t see the round ones,” says Uapwanawa Muhenije, a Himba woman from a village in northern Namibia, speaking through an interpreter over a Zoom interview. “I wonder how you can’t see them.” Muhenije didn’t participate in the research because her village is less remote than those in the study, and it includes rectangular as well as circular buildings. She sees both shapes in the Coffer illusion easily. Although the study found dramatic differences in how people see four illusions, “the one experiment that’s going to overwhelm people is this Coffer,” says Jules Davidoff, a psychologist at the University of London who was not involved in the study. “There are other striking cultural differences in perception, but the one that they’ve produced here is a real humdinger.” The findings were published as a preprint on the PsyArXiv in February and updated this week. © 2025 American Association for the Advancement of Science.

Related chapters from BN: Chapter 7: Life-Span Development of the Brain and Behavior; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 13: Memory and Learning; Chapter 7: Vision: From Eye to Brain
Link ID: 29838 - Posted: 06.21.2025

Anna Bawden Health and social affairs correspondent Weight loss drugs could at least double the risk of diabetic patients developing age-related macular degeneration, a large-scale study has found. Originally developed for diabetes patients, glucagon-like peptide-1 receptor agonist (GLP-1 RA) medicines have transformed how obesity is treated and there is growing evidence of wider health benefits. They help reduce blood sugar levels, slow digestion and reduce appetite. But a study by Canadian scientists published in Jama Ophthalmology has found that after six months of use GLP-1 RAs are associated with double the risk of older people with diabetes developing neovascular age-related macular degeneration compared with similar patients not taking the drugs. Academics at the University of Toronto examined medical data for more than 1 million Ontario residents with a diagnosis of diabetes and identified 46,334 patients with an average age of 66 who were prescribed GLP-1 RAs. Nearly all (97.5%) were taking semaglutide, while 2.5% were on lixisenatide. The study did not exclude any specific brand of drugs, but since Wegovy was only approved in Canada in November 2021, primarily for weight loss, it is likely the bulk of semaglutide users in the study were taking Ozempic, which is prescribed for diabetes. Each patient on semaglutide or lixisenatide was matched with two patients who also had diabetes but were not taking the drugs, who shared similar characteristics such as age, gender and health conditions. The researchers then compared how many patients developed neovascular age-related macular degeneration over three years. © 2025 Guardian News & Media Limited

Related chapters from BN: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment; Chapter 7: Vision: From Eye to Brain
Link ID: 29822 - Posted: 06.07.2025