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When you walk into a room, your eyes process your surroundings immediately: refrigerator, sink, table, chairs. "This is the kitchen," you realize. Your brain has taken data and come to a clear conclusion about the world around you, in an instant. But how does this actually happen? Elissa Aminoff, a research scientist in the Department of Psychology and the Center for the Neural Basis of Cognition at Carnegie Mellon University, shares her insights on what computer modeling can tell us about human vision and memory. What do you do? What interests me is how the brain and the mind understand our visual environment. The visual world is really rich with information, and it’s extremely complex. So we have to find ways to break visual data down. What specific parts of our [visual] world is the brain using to give us what we see? In order to answer that question, we’re collaborating with computer scientists and using computer vision algorithms. The goal is to compare these digital methods with the brain. Perhaps they can help us find out what types of data the brain is working with. Does that mean that our brains function like a computer? That’s something you hear a lot about these days. No, I wouldn’t say that. It’s that computers are giving us the closest thing that we have right now to an analogous mechanism. The brain is really, really complex. It deals with massive amounts of data. We need help in organizing these data and computers can do that. Right now, there are algorithms that can identify an object as a phone or as a mug, just like the brain. But are they doing the same thing? Probably not. © 2016 Scientific American,

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 22379 - Posted: 06.30.2016

By Aviva Rutkin Machine minds are often described as black boxes, their decision-making processes all but inscrutable. But in the case of machine intelligence, researchers are cracking that black box open and peering inside. What they find is that humans and machines don’t pay attention to the same things when they look at pictures – not at all. Researchers at Facebook and Virginia Tech in Blacksburg got humans and machines to look at pictures and answer simple questions – a task that neural-network-based artificial intelligence can handle. But the researchers weren’t interested in the answers. They wanted to map human and AI attention, in order to shed a little light on the differences between us and them. “These attention maps are something we can measure in both humans and machines, which is pretty rare,” says Lawrence Zitnick at Facebook AI Research. Comparing the two could provide insight “into whether computers are looking in the right place”. First, Zitnick and his colleagues asked human workers on Amazon Mechanical Turk to answer simple questions about a set of pictures, such as “What is the man doing?” or “What number of cats are lying on the bed?” Each picture was blurred, and the worker would have to click around to sharpen it. A map of those clicks served as a guide to what part of the picture they were paying attention to. © Copyright Reed Business Information Ltd.

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 22378 - Posted: 06.30.2016

Worldwide voting for the BEST ILLUSION OF THE YEAR will take place online from 4pm EST on June 29th to 4pm EST on June 30th. The winning illusions will receive a $3,000 award for 1st place, a $2,000 award for 2nd place, and a $1,000 award for 3rd place. Anybody with an internet connection (that means YOU!) can vote to pick the Top 3 Winners from the current Top 10 List! The Best illusion of the Year Contest is a celebration of the ingenuity and creativity of the world’s premier illusion research community. Contestants from all around the world submitted novel illusions (unpublished, or published no earlier than 2015), and an international panel of judges rated them and narrowed them to the TOP TEN.

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 22375 - Posted: 06.29.2016

By Vinicius Donisete Goulart The “new world” monkeys of South and Central America range from large muriquis to tiny pygmy marmosets. Some are cute and furry, others bald and bright red, and one even has an extraordinary moustache. Yet, with the exception of owl and howler monkeys, the 130 or so remaining species have one thing in common: A good chunk of the females, and all of the males, are colorblind. This is quite different from “old world” primates, including us Homo sapiens, who are routinely able to see the world in what we humans imagine as full color. In evolutionary terms, colorblindness sounds like a disadvantage, one which should really have been eliminated by natural selection long ago. So how can we explain a continent of the colorblind monkeys? I have long wondered what makes primates in the region colorblind and visually diverse, and how evolutionary forces are acting to maintain this variation. We don’t yet know exactly what kept these seemingly disadvantaged monkeys alive and flourishing—but what is becoming clear is that colorblindness is an adaptation not a defect. The first thing to understand is that what we humans consider “color” is only a small portion of the spectrum. Our “trichromatic” vision is superior to most mammals, who typically share the “dichromatic” vision of new world monkeys and colorblind humans, yet fish, amphibians, reptiles, birds, and even insects are able to see a wider range, even into the UV spectrum. There is a whole world of color out there that humans and our primate cousins are unaware of. What is becoming clear is that color blindness is an adaptation not a defect.

Related chapters from BP7e: 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: 22345 - Posted: 06.22.2016

By Sarah Kaplan Some 250 million years ago, when dinosaurs roamed the Earth and early mammals were little more than tiny, fuzzy creatures that scurried around attempting to evade notice, our ancestors evolved a nifty trick. They started to become active at night. They developed sensitive whiskers and an acute sense of hearing. Their circadian rhythms shifted to let them sleep during the day. Most importantly, the composition of their eyes changed — instead of color-sensing cone photoreceptor cells, they gained thousands of light-sensitive rod cells, which allowed them to navigate a landscape lit only by the moon and stars. Mammals may no longer have to hide from the dinosaurs, but we bear the indelible marks of our scrappy, nocturnal past. Unlike every other vertebrate on land and sea, we still have rod-dominated eyes — human retinas, for example, are 95 percent rods, even though we're no longer active at night. "How did that happen? What is the mechanism that made mammals become so different?" asked Anand Swaroop, chief of the Neurobiology Neurodegeneration and Repair Laboratory at the National Eye Institute. He provides some answers to those questions in a study published in the journal Developmental Cell Monday. The findings are interesting from an evolutionary standpoint, he said, but they're also the keys to a medical mystery. If Swaroop and his colleagues can understand how our eyes evolved, perhaps they can fix some of the problems that evolved with them.

Related chapters from BP7e: 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: 22342 - Posted: 06.21.2016

By Stephen L. Macknik Every few decades there’s a major new neuroscience discovery that changes everything. I’m not talking about your garden variety discovery. Those happen frequently (this is the golden age of neuroscience after all). But no, what I’m talking about are the holy-moly, scales-falling-from-your-eyes, time-to-rewrite-the-textbooks, game-changing discoveries. Well one was reported in this last month—simultaneously by two separate labs—and it redefines the primary organizational principle of the visual system in the cortex of the brain. This may sound technical, but it concerns how we see light and dark, and the perception of contrast. Since all sensation functions at the pleasure of contrast, these new discoveries impact neuroscience and psychology as a whole. I’ll explain below. The old way of thinking about how the wiring of the visual cortex was organized orbited around the concept of visual-edge orientation. David Hubel (my old mentor) and Torsten Wiesel (my current fellow Brooklynite)—who shared the Nobel Prize in Physiology or Medicine in 1981—arguably made the first major breakthrough concerning how information was organized in the cortex versus earlier stages of visual processing. Before their discovery, the retina (and the whole visual system) was thought to be a kind of neural camera that communicated its image into the brain. The optic nerves connect the eyes’ retinas to the thalamus at the center of the brain—and then the thalamus connects to the visual cortex at the back of the brain through a neural information superhighway called the optic radiations. Scientists knew, even way back then, that neurons at a given point of the visual scene lie physically next to the neuron that sees the neighboring piece of the visual scene. The discovery of this so called retinotopic map in the primary visual cortex (by Talbot and Marshall) was of course important, but because it matched the retinotopic mapping of the retina and thalamus, it didn’t constitute a new way of thinking. It wasn’t a game-changing discovery. © 2016 Scientific American

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 22301 - Posted: 06.09.2016

By Jordana Cepelewicz Colors exist on a seamless spectrum, yet we assign hues to discrete categories such as “red” and “orange.” Past studies have found that a person's native language can influence the way colors are categorized and even perceived. In Russian, for example, light blue and dark blue are named as different colors, and studies find that Russian speakers can more readily distinguish between the shades. Yet scientists have wondered about the extent of such verbal influence. Are color categories purely a construct of language, or is there a physiological basis for the distinction between green and blue? A new study in infants suggests that even before acquiring language, our brain already sorts colors into the familiar groups. A team of researchers in Japan tracked neural activity in 12 prelinguistic infants as they looked at a series of geometric figures. When the shapes' color switched between green and blue, activity increased in the occipitotemporal region of the brain, an area known to process visual stimuli. When the color changed within a category, such as between two shades of green, brain activity remained steady. The team found the same pattern in six adult participants. The infants used both brain hemispheres to process color changes. Language areas are usually in the left hemisphere, so the finding provides further evidence that color categorization is not entirely dependent on language. At some point as a child grows, language must start playing a role—just ask a Russian whether a cloudless sky is the same color as the deep sea. The researchers hope to study that developmental process next. “Our results imply that the categorical color distinctions arise before the development of linguistic abilities,” says Jiale Yang, a psychologist at Chuo University and lead author of the study, published in February in PNAS. “But maybe they are later shaped by language learning.” © 2016 Scientific American

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory, Learning, and Development
Link ID: 22291 - Posted: 06.07.2016

By Jane E. Brody Joanne Reitano is a professor of history at LaGuardia Community College in Long Island City, Queens. She writes wonderful books about the history of the city and state, and has recently been spending many hours — sometimes all day — at her computer to revise her first book, “The Restless City.” But while sitting in front of the screen, she told me, “I developed burning in my eyes that made it very difficult to work.” After resting her eyes for a while, the discomfort abates, but it quickly returns when she goes back to the computer. “If I was playing computer games, I’d turn off the computer, but I need it to work,” the frustrated professor said. Dr. Reitano has a condition called computer vision syndrome. She is hardly alone. It can affect anyone who spends three or more hours a day in front of computer monitors, and the population at risk is potentially huge. Worldwide, up to 70 million workers are at risk for computer vision syndrome, and those numbers are only likely to grow. In a report about the condition written by eye care specialists in Nigeria and Botswana and published in Medical Practice and Reviews, the authors detail an expanding list of professionals at risk — accountants, architects, bankers, engineers, flight controllers, graphic artists, journalists, academicians, secretaries and students — all of whom “cannot work without the help of computer.” And that’s not counting the millions of children and adolescents who spend many hours a day playing computer games. Studies have indicated 70 percent to 90 percent of people who use computers extensively, whether for work or play, have one or more symptoms of computer vision syndrome. The effects of prolonged computer use are not just vision-related. Complaints include neurological symptoms like chronic headaches and musculoskeletal problems like neck and back pain. © 2016 The New York Times Company

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 22262 - Posted: 05.30.2016

Sara Reardon Every time something poked its foot, the mouse jumped in pain. Researchers at Circuit Therapeutics, a start-up company in Menlo Park, California, had made the animal hypersensitive to touch by tying off a nerve in its leg. But when they shone a yellow light on its foot while poking it, the mouse did not react. The treatment is one of several nearing clinical use that draw on optogenetics — a technique in which light is used to control genes and neuron firing. In March, RetroSense Therapeutics of Ann Arbor, Michigan, began the first clinical-safety trial of an optogenetic therapy to treat the vision disorder retinitis pigmentosa. Many scientists are waiting to see how the trial turns out before they decide how to move forward with their own research on a number of different applications. “I think it will embolden people if there’s good news,” says Robert Gereau, a pain researcher at Washington University in St Louis, Missouri. “It opens up a whole new range of possiblilities for how to treat neurological diseases.” Retinitis pigmentosa destroys photoreceptors in the eye. RetroSense’s treatment seeks to compensate for this loss by conferring light sensitivity to retinal ganglion cells, which normally help to pass visual signals from photoreceptors to the brain. The therapy involves injecting patients who are blind or mostly blind with viruses carrying genes that encode light-sensitive proteins called opsins. The cells fire when stimulated with blue light, passing the visual information to the brain. Chief executive Sean Ainsworth says that the company has injected several individuals in the United States with the treatment, and plans to enroll a total of 15 blind patients in its trial. RetroSense will follow them for two years, but may release some preliminary data later this year. © 2016 Nature Publishing Group

Related chapters from BP7e: 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: Neurophysiology: The Generation, Transmission, and Integration of Neural Signals
Link ID: 22235 - Posted: 05.21.2016

By Roni Caryn Rabin Here’s another reason to eat your fruits and veggies: You may reduce your risk of vision loss from cataracts. Cataracts that cloud the lenses of the eye develop naturally with age, but a new study is one of the first to suggest that diet may play a greater role than genetics in their progression. Researchers had about 1,000 pairs of female twins in Britain fill out detailed food questionnaires that tracked their nutrient intake. Their mean age was just over 60. The study participants underwent digital imaging of the eye to measure the progression of cataracts. The researchers found that women who consumed diets rich in vitamin C and who ate about two servings of fruit and two servings of vegetables a day had a 20 percent lower risk of cataracts than those who ate a less nutrient-rich diet. Ten years later, the scientists followed up with 324 of the twin pairs, and found that those who had reported consuming more vitamin C in their diet — at least twice the recommended dietary allowance of 75 milligrams a day for women (the R.D.A. for adult men is 90 milligrams) — had a 33 percent lower risk of their cataracts progressing than those who get less vitamin C. The researchers concluded that genetic factors account for about 35 percent of the difference in cataract progression, while environmental factors like diet account for 65 percent. “We found no beneficial effect from supplements, only from the vitamin C in the diet,” said Dr. Christopher Hammond, a professor of ophthalmology at King’s College London and an author of the study,published in Ophthalmology. Foods high in vitamin C include oranges, cantaloupe, kiwi, broccoli and dark leafy greens. © 2016 The New York Times Company

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 22044 - Posted: 03.29.2016

Monya Baker A surgical technique to treat cataracts in children spurs stem cells to generate a new, clear lens. Discs made of multiple types of eye tissue have been grown from human stem cells — and that tissue has been used to restore sight in rabbits. The work, reported today in Nature1, suggests that induced pluripotent stem (iPS) cells — stem cells generated from adult cells — could one day be harnessed to provide replacement corneal or lens tissue for human eyes. The discs also could be used to study how eye tissue and congenital eye diseases develop. “The potential of this technique is mind-boggling,” says Mark Daniell, head of corneal research at the Centre for Eye Research Australia in Melbourne, who was not involved in the research. “It’s almost like an eye in a dish.” A second, unrelated paper in Nature2 describes a surgical procedure that activates the body’s own stem cells to regenerate a clear, functioning lens in the eyes of babies born with cataracts. The two studies are “amazing, almost like science fiction”, Daniell says. In the first study, a team led by Kohji Nishida, an ophthalmologist at Osaka University Graduate School of Medicine in Japan, cultivated human iPS cells to produce discs that contained several types of eye tissue. © 2016 Nature Publishing Group

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21971 - Posted: 03.10.2016

By Virginia Morell Butterflies may not have a human’s sharp vision, but their eyes beat us in other ways. Their visual fields are larger, they’re better at perceiving fast-moving objects, and they can distinguish ultraviolet and polarized light. Now, it turns out that one species of swallowtail butterfly from Australasia, the common bluebottle (Graphium sarpedon, pictured), known for its conspicuous blue-green markings, is even better equipped for such visual tasks. Each of their eyes, scientists report in Frontiers in Ecology and Evolution, contains at least 15 different types of photoreceptors, the light-detecting cells required for color vision. These are comparable to the rods and cones found in our eyes. To understand how the spectrally complex retinas of butterflies evolved, the researchers used physiological, anatomical, and molecular experiments to examine the eyes of 200 male bluebottles collected in Japan. (Only males were used because the scientists failed to catch a sufficient number of females.) They found that different colors stimulate each class of receptor. For instance, UV light stimulates one, while slightly different blue lights set off three others; and green lights trigger four more. Most insect species have only three classes of photoreceptors. Even humans have only three cones, yet we still see millions of colors. Butterflies need only four receptor classes for color vision, including spectra in the UV region. So why did this species evolve 11 more? The scientists suspect that some of the receptors must be tuned to perceive specific things of great ecological importance to these iridescent butterflies—such as sex. For instance, with eyes alert to the slightest variation in the blue-green spectrum, male bluebottles can spot and chase their rivals, even when they’re flying against a blue sky. © 2016 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21968 - Posted: 03.09.2016

Our eyes constantly send bits of information about the world around us to our brains where the information is assembled into objects we recognize. Along the way, a series of neurons in the eye uses electrical and chemical signals to relay the information. In a study of mice, National Institutes of Health scientists showed how one type of neuron may do this to distinguish moving objects. The study suggests that the NMDA receptor, a protein normally associated with learning and memory, may help neurons in the eye and the brain relay that information. “The eye is a window onto the outside world and the inner workings of the brain,” said Jeffrey S. Diamond, Ph.D., senior scientist at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), and the senior author of the study published in Neuron. “Our results show how neurons in the eye and the brain may use NMDA receptors to help them detect motion in a complex visual world.” Vision begins when light enters the eye and hits the retina, which lines the back of the eyeball. Neurons in the retina convert light into nerve signals which are then sent to the brain. Using retinas isolated from mice, Dr. Alon Poleg-Polsky, Ph.D. a postdoctoral fellow in Dr. Diamond’s lab, studied neurons called directionally selective retinal ganglion cells (DSGCs), which are known to fire and send signals to the brain in response to objects moving in specific directions across the eye. Electrical recordings showed that some of these cells fired when a bar of light passed across the retina from left to right, whereas others responded to light crossing in the opposite direction. Previous studies suggested these unique responses are controlled by incoming signals sent from neighboring cells at chemical communication points called synapses. In this study, Dr. Poleg-Polsky discovered that the activity of NMDA receptors at one set of synapses may regulate whether DSGCs sent direction-sensitive information to the brain.

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21966 - Posted: 03.08.2016

By C. CLAIBORNE RAY Q. What’s the No. 1 cause of blindness in seniors in the United States? A. “It sounds like a simple question, but there’s no perfect answer,” said Dr. Susan Vitale, a research epidemiologist at the National Eye Institute of the National Institutes of Health. “It depends on age, how blindness is measured and how statistics are collected.” For example, some studies have relied on the self-reported answer to the vague question: “Do you have vision problems?” The best available estimates, she said, come from a 2004 paper aggregating many other studies, some in the United States and some in other countries, updated by applying later census data. This paper and others have found striking differences by age and by racial and socioeconomic groups, Dr. Vitale said. In white people, she said, the major cause of blindness at older ages is usually age-related macular degeneration, progressive damage to the central portion of the retina. In older black people, the major causes are likely to be glaucoma or cataracts. In older people of working age, from their 40s to their 60s, the major cause, regardless of race, is diabetic retinopathy, damage to the retina as a result of diabetes. Many studies have shown that white people are more likely to have age-related macular degeneration, Dr. Vitale said, but as for cataracts, for which blindness is preventable by surgery, there are questions about access to health care and whether those affected can get the needed surgery. It is not known why black people are at higher risk of glaucoma. There are also some gender differences, she said, with white women more likely than white men to become blind. Studies have not found the same difference by gender in black and Hispanic people. Because many of the causes of blindness at all ages are preventable, Dr. Vitale said, it is essential to have regular eye checkups, even if there are no obvious symptoms. © 2016 The New York Times Company

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21958 - Posted: 03.07.2016

By Susana Martinez-Conde, Stephen L. Macknik In the forests of Australia and New Guinea lives a pigeon-sized creature that is not only a master builder but a clever illusionist, too. The great bowerbird (Chlamydera nuchalis)—a cousin of crows and jays—has an elaborate mating ritual that relies on the male's ability to conjure forced perspective. Throughout the year he painstakingly builds and maintains his bower: a 60-centimeter-long corridor made of twigs, leading to a courtyard decorated with gray and white pebbles, shells and bones. Some species also add flowers, fruits, feathers, bottle caps, acorns, abandoned toys—whatever colorful knickknacks they can find. The male takes great care to arrange the objects according to size so that the smallest pieces are closest to the bower's entrance and the largest items are farthest away. The elaborate structure is not a nest. Its sole purpose is to attract a female for mating. Once construction is complete, the male performs in the courtyard for a visiting female, who—poised like a critical American Idol judge—evaluates the routine from the middle of the corridor. He sings, dances and prances, tossing around a few select trinkets to impress his potential mate. Her viewpoint is very narrow, and so she perceives objects paving the courtyard as being uniform in size. This forced perspective makes the choice offerings appear grander and therefore all the more enticing. The offerings, and the male himself, appear larger than life because of an effect that visual scientists call the Ebbinghaus illusion, which causes an object to look bigger if it is surrounded by smaller objects. © 2016 Scientific American

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 8: Hormones and Sex
Link ID: 21912 - Posted: 02.19.2016

Floaters, those small dots or cobweb-shaped patches that move or “float” through the field of vision, can be alarming. Though many are harmless, if you develop a new floater, “you need to be seen pretty quickly” by an eye doctor in order to rule out a retinal tear or detachment, said Dr. Rebecca Taylor, a spokeswoman for the American Academy of Ophthalmology. Floaters are caused by clumping of the vitreous humor, the gel-like fluid that fills the inside of the eye. Normally, the vitreous gel is anchored to the back of the eye. But as you age, it tends to thin out and may shrink and pull away from the inside surface of the eye, causing clumps or strands of connective tissue to become lodged in the jelly, much as “strands of thread fray when a button comes off on your coat,” Dr. Taylor said. The strands or clumps cast shadows on the retina, appearing as specks, dots, clouds or spider webs in your field of vision. Such changes may occur at younger ages, too, particularly if you are nearsighted or have had a head injury or eye surgery. There is no treatment for floaters, though they usually fade with time. But it’s still important to see a doctor if new floaters arise because the detaching vitreous gel can pull on the retina, causing it to tear, which can lead to retinal detachment, a serious condition. The pulling or tugging on the retina may be perceived as lightning-like flashes, “like a strobe light off to the side of your vision,” Dr. Taylor said. See an eye doctor within 24 to 48 hours if you have a new floater, experience a sudden “storm” of floaters, see a gray curtain or shadow move across your field of vision, or have a sudden decrease in vision. © 2016 The New York Times Company

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21868 - Posted: 02.08.2016

By Susana Martinez-Conde Take a look at the red chips on the two Rubik cubes below. They are actually orange on the left and purple on the right, if you look at them in isolation. They only appear more or less equally red across the images because your brain is interpreting them as red chips lit by either yellow or blue light. This kind of misperception is an example of perceptual constancy, the mechanism that allows you to recognize an object as being the same in different environments, and under very diverse lighting conditions. Constancy illusions are adaptive: consider what would have happened if your ancestors thought a friend became a foe whenever a cloud hid the sun, or if they lost track of their belongings–and even their own children—every time they stepped out of the cave and into the sunlight. Why, they might have even eaten their own kids! You are here because the perceptual systems of your predecessors were resistant to annoying changes in the physical reality–as is your own (adult) perception. There are many indications that constancy effects must have helped us survive (and continue to do so). One such clue is that we are not born with perceptual constancy, but develop it many months after birth. So at first we see all differences, and then we learn to ignore certain types of differences so that we can recognize the same object as unchanging in many varied scenarios. When perceptual constancy arises, we lose the ability to detect multiple contradictions that are nevertheless highly noticeable to young babies. © 2016 Scientific American

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 7: Vision: From Eye to Brain; Chapter 13: Memory, Learning, and Development
Link ID: 21858 - Posted: 02.04.2016

By Ana Swanson Earlier this year, the famous blue-and-black (or white-and-gold) dress captivated the Internet, serving as a reminder that color is truly in the eye of the beholder. The dress was also a lesson in the power of social media, the science of shifting colors, and the fun of optical illusions. Here we present a visual story from February 27 that rounded up some of the best-known optical illusions on the Web. The Internet erupted in an energetic debate yesterday about whether an ugly dress was blue and black or white and gold, with celebrities from Anna Kendrick (white) to Taylor Swift (black) weighing in. (For the record, I’m with Taylor – never a bad camp to be in.) It sounds inane, but the dress question was actually tricky: Some declared themselves firmly in the blue and black camp, only to have the dress appear white and gold when they looked back a few hours later. Wired had the best explanation of the science behind the dress’s shifting colors. When your brain tries to figure out what color something is, it essentially subtracts the lighting and background colors around it, or as the neuroscientist interviewed by Wired says, tries to “discount the chromatic bias of the daylight axis.” This is why you can identify an apple as red whether you see it at noon or at dusk. The dress is on some kind of perceptual boundary, with a pretty even mix of blue, red and green. (Frankly, it’s just a terrible, washed out photo.) So for those who see it as white, your eyes may be subtracting the wrong background and lighting.

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21742 - Posted: 01.02.2016

By John Bohannon It may sound like a bird-brained idea, but scientists have trained pigeons to spot cancer in images of biopsied tissue. Individually, the avian analysts can't quite match the accuracy of professional pathologists. But as a flock, they did as well as trained humans, according to a new study appearing this week in PLOS ONE. Cancer diagnosis often begins as a visual challenge: Does this lumpy spot in a mammogram image justify a biopsy? And do cells in biopsy slides look malignant or benign? Training doctors and medical technicians to tell the difference is expensive and time-consuming, and computers aren't yet up to the task. To see whether a different type of trainee could do better, a team led by Richard Levenson, a pathologist and technologist at the University of California, Davis, and Edward Wasserman, a psychologist at the University of Iowa, in Iowa City, turned to pigeons. In spite of their limited intellect, the bobble-headed birds have certain advantages. They have excellent visual systems, similar to, if not better than, a human's. They sense five different colors as opposed to our three, and they don’t “fill in” the gaps like we do when expected shapes are missing. However, training animals to do a sophisticated task is tricky. Animals can pick up on unintentional cues from their trainers and other humans that may help them correctly solve problems. For example, a famous 20th century horse named Clever Hans was purportedly able to do simple arithmetic, but was later shown to be observing the reactions of his human audience. And although animals can perform extremely well on tasks that are confined to limited circumstances, overtraining on one set of materials can lead to total inaccuracy when the same information is conveyed slightly differently. © 2015 American Association for the Advancement of Science

Related chapters from BP7e: Chapter 17: Learning and Memory; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 13: Memory, Learning, and Development; Chapter 7: Vision: From Eye to Brain
Link ID: 21652 - Posted: 11.21.2015

Susan Milius Certain species of the crawling lumps of mollusk called chitons polka-dot their armor-plated backs with hundreds of tiny black eyes. But mixing protection and vision can come at a price. The lenses are rocky nuggets formed mostly of aragonite, the same mineral that pearls and abalone shells are made of. New analyses of these eyes support previous evidence that they form rough images instead of just sensing overall lightness or darkness, says materials scientist Ling Li of Harvard University. Adding eyes to armor does introduce weak spots in the shell. Yet the positioning of the eyes and their growth habits show how chitons compensate for that, Li and his colleagues report in the November 20 Science. Li and coauthor Christine Ortiz of MIT have been studying such trade-offs in biological materials that serve multiple functions. Human designers often need substances that multitask, and the researchers have turned to evolution’s solutions in chitons and other organisms for inspiration. Biologists had known that dozens of chiton species sprinkle their armored plates with simple-seeming eye spots. (The armor has other sensory organs: pores even tinier than the eyes.) But in 2011, a research team showed that the eyes of the West Indian fuzzy chiton (Acanthopleura granulata) were much more remarkable than anyone had realized. Their unusual aragonite lens can detect the difference between a looming black circle and a generally gray field of vision. Researchers could tell because chitons clamped their shells defensively to the bottom when a scary circle appeared but not when an artificial sky turned overall shadowy. © Society for Science & the Public 2000 - 2015

Related chapters from BP7e: Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 7: Vision: From Eye to Brain
Link ID: 21646 - Posted: 11.20.2015