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7/28/2019 Science Jua

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THE (KIDS') EYES HAVE IT

In a new study of visual abilities, researchers asked volunteers to identifythe biggest orange circle. Here, each orange circle on the right is a little bitlarger than the one on the left. Misleading images usually fooled adults butnot children, while helpful images greatly aided adults but not kids.

-M. Doherty

Can you believe your eyes? A recent experiment suggests that the answer to that questionmay depend on your age.

In the experiment, kids and adults were asked to look at the same visual illusion a picturethat was designed to trick the viewer. The researchers who ran the experiment say that adultswere more easily fooled by the illusion, and that the kids, especially those younger than age7, saw the picture more accurately.

Martin Doherty, a psychologist at the University of Stirling in Scotland, led the team ofscientists. A psychologist is a scientist who studies behavior and processes in the brain andmay offer counseling to patients. Doherty says that his experiment can tell scientistssomething about how the human brain develops. In particular, the experiment shows thatwhat the brain does to "see" visual context is a process that develops slowly.

The words visual context refer to how a person sees something in relation to the thingsaround it. A baseball may look large when next to a golf ball, for example, but appear smallwhen next to a basketball.

In this experiment, Doherty and his team tested the perception of the participants usingpictures of solid orange circles. The researchers showed the same pictures to two groups ofpeople. The first group included 151 children ages 4 to 10, and the second group included 24adults of ages 18 to 25.

The first group of pictures showed two circles alone on a white background. One of the circleswas larger than the other, and the participants were asked to identify the larger one. Four-year-olds identified the correct circle 79 percent of the time. Adults identified the correct circle95 percent of the time.

Next, both groups were shown a picture where the orange circles, again of different sizes,were surrounded by gray circles. Heres where the illusion came in remember the

baseballs, golf balls and basketballs.


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If an orange circle is surrounded by smaller gray circles, then it appears larger than it really is.If an orange circle is surrounded by larger gray circles, then it appears smaller than it really is.

But the experiments added a twist: In some of the pictures, the smaller orange circle wassurrounded by even smaller gray circles making the orange circle appear larger than theother orange circle, which was the real larger one. And the larger orange circle was

surrounded by even bigger gray circles so it appeared to be smaller than the real smallerorange circle.

When young children ages 4 to 6 looked at these tricky pictures, they werent fooled theywere still able to find the bigger circle with roughly the same accuracy as before. Olderchildren and adults, on the other hand, did not do as well. Older children often identified thesmaller circle as the larger one, and adults got it wrong most of the time.

When visual context is misleading, adults literally see the world less accurately than they didas children, Doherty told Science News.

As children get older, Doherty said, their brains may develop the ability to perceive visual

context. In other words, they will begin to process the whole picture at once: the tricky graycircles, as well as the orange circle in the middle. As a result, theyre more likely to fall for thiskind of visual trick.

Doherty is not the first scientist to study visual context in children, and earlier studies havefound that children, just like adults, can be fooled by illusion. Carl Granrud is a psychologist atthe University of Northern Colorado in Greeley. He told Science News that Dohertys findingsseem sound, but that they were somewhat surprising. He pointed out that in other visualillusion tests, children were fooled, suggesting they had developed the ability to see visualcontext.

This experiment shows that sometimes, in order to get a sneak peek inside the brain, youhave to try to trick it and see what happens.


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STARS

A star begins its life in a dense molecular cloudcalled a nebula. Shown here is the HorseheadNebula.

Jean-Charles Cuillandre, Hawaiian Starlight,Canada-France-Hawaii Telescope

As long as people have been living on Earth, weve been looking up at bright stars in the night

sky, trying to understand the universe and our place in it. Astronomers have long known thatnot all stars are alike. Some are almost as old as the universe itself, others are just now beingborn. They come in different colors: blue, white, yellow and red. Some shine brightly in thesky, and others are visible only with special telescopes. Some stars race through space inpairs or groups; others move alone. Some, like our own 4.8-billion year-old sun, aresurrounded by planets.

One of the most important ways that scientists group stars is by size. In the early 20thcentury, just before World War I, astronomers began to put stars into two main size groups:dwarfs and giants.

Once they discovered that there was a class of stars really big, called giants, they carved theuniverse up into dwarfs and giants, says Jim Holberg, a scientist who studies dwarf stars at

the University of Arizona in Tucson. The giants are enormous stars, and dwarfs are stars likethe sun.

Despite their name, most dwarf stars are not unusually small. Or unusual at all: Most stars, infact, are dwarfs of one kind or another. But within the large category of dwarf stars are othergroups of stars. Keeping track of the different kinds of dwarfs can be difficult, but thats all in adays work for astronomers.


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A BROWN DWARF MYSTERY: PLANETS, STARS OR NEITHER?

The tiny dot on the right side of this picture is the first verifiedimage of a brown dwarf. This image was taken in 1995 by acamera onboard the Hubble Space Telescope. The browndwarf shown here is orbiting a much larger, brighter star

called Gliese 229.

S. Durrance and D. Golimowski (JHU), NASA

Some objects are so strange that even astronomers arent sure what to call them. One ofthese kinds of objects behaves like a star, but its not very hot and its too small. Plus,through a telescope, it resembles a planet but its too big to be called one. What would youcall it? A star-net? A planet-ar?

An American astronomer named Shiv Kumar first predicted these strange objects might existin 1963, and he called them black dwarfs. That name didnt stick, and ten years later anotherastronomer suggested the name brown dwarfs. That name stuck.

But there was another problem: Even though astronomers like Kumar could use informationto imagine how brown dwarfs should behave, no one had ever seen one. It wasnt until 1995 just 14 years ago that astronomers first saw one of these brown dwarfs. Since that firstdiscovery, astronomers have found hundreds more brown dwarfs.

Thanks to more scientists looking for these stars, and better telescopes to see them with,astronomers now know more about brown dwarfs. As it turns out, they arent even brown.They are almost totally dark in the sky, producing no visible light. Instead, they emit infraredlight, which is so faint it can only be detected by sophisticated telescopes.

Also, brown dwarfs arent even stars. Some astronomers even call brown dwarfs failed

stars.


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When you see a star in the sky, it looks like a calm, twinkling light. Your eyes deceive you,however. A star is anything but calm: What you are really looking at it is a giant, fiery ball ofburning gas. For most stars, that gas is hydrogen, the lightest element in the universe.Hydrogen is the fuel for stars, just as gasoline is the fuel for most modern cars.

Stars are powered by a process called fusion, where hydrogen atoms join together to form

helium and give off a lot of energy. Like stars, brown dwarfs have a lot of hydrogen. Butunlike other stars, brown dwarfs dont have enough mass to start the fusion process. Soinstead of burning bright and hot their whole lives, brown dwarfs smolder slowly and donttechnically qualify as stars.

This illustration of a brown dwarf studied by Phan Bao Ngoc and otherscientists shows jets of gas shooting out. These jets tell astronomers thatthe brown dwarf formed more like a star than a planet.

David A. Aguilar (Harvard Smithsonian Center for Astrophysics)

In December 2008, astronomer Phan Bao Ngoc, who studies brown dwarfs at the AcademiaSinica Institute of Astronomy and Astrophysics in Taiwan, and a team of scientists solved onemystery about brown dwarfs. They showed that brown dwarfs shoot out a stream of gas intospace like stars. Thus, the strange objects seem to form more like stars than like planets.But, Ngoc cautions, that doesnt make them stars. It is still too early to say this settles alldebate. We need to observe more young brown dwarfs, he says. This opens a new windowand provides an important clue for the brown dwarf formation theory.

Red dwarf stars: the most popular stars youll never see

In April 2007, astronomers introduced a planet circling a reddwarf called Gliese 581 c, illustrated here. The planet is onlya little larger than Earth, and though it probably could not

sustain life, the discovery gives hope to scientists who arelooking for extraterrestrial life.


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ESO

Objects in space that have just a little more mass than brown dwarfs are called red dwarfstars. Red dwarfs may not be much larger than brown dwarfs, but that small increase in sizemakes a big difference. Red dwarf stars are massive enough to support hydrogen fusion, like

the sun. And theyre also technically stars.

But unlike the sun, red dwarfs dont shine in the sky. Theyre less massive, and they dontproduce as much energy, says Holberg. They dont have a strong energy source, so theyreburning at a low rate. Most of the energy red dwarfs produce is invisible to the naked eye butvisible to high-powered telescopes.

Despite the difficulty in finding these stars, astronomers believe that most of the stars in ourgalaxy are red dwarfs. The suns nearest neighbor, Proxima Centauri, is a red dwarf morethan 20 trillion miles away. Most of our nearest star neighbors are red dwarfs.

TWO MONKEYS SEE A MORE COLORFUL WORLD

A colorblind male squirrel monkey named Dalton is pictured heretaking a color vision test.

Neitz Laboratory, University of Washington

For a pair of squirrel monkeys named Sam and Dalton, the world recently got more colorful.Male squirrel monkeys are normally red-green colorblind, which means they have troubleseeing those colors. But now, thanks to an experiment by scientists at the University ofSeattle, Sam and Dalton see things differentlythey seem to be able to see red and green.

Animals (including people) are able to see different colors of light thanks to proteins in theeye. Proteins are important building blocks of cells, and different kinds of proteins servespecific purposes in a living organism. When an important protein is absent or disabled, theanimal cannot function properly. Male squirrel monkeys normally lack the proteins that detectred and green light, which means they cant tell red and green from other colors. Themonkeys can see blue and yellow.

Jay Neitz is the scientist at the University of Washington who led the research to give themonkeys more colorful vision. He says the experiment wasnt supposed to work. In fact, whenhe asked other scientists who study vision if they thought color vision was possible incolorblind monkeys, every single person said, absolutely not, he says.

Neitz and his team were able to add genes that make proteins for detecting red light in themonkeys eyes. A gene is like a recipe for building a protein, and different genes direct thebody how to build different proteins. Almost every cell of a living organism contain DNA, or


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deoxyribonucleic acid, which is the set of instructions for how to make that organism function.These instructions include all the genes, which are segments of DNA.

A gene is also responsible for building the protein that enables an animal to see the color red.Neitz and his team found male squirrel monkeys that dont have this geneso for theirexperiment, they tried to give the gene to the monkeys. They injected the monkeys with a

virus that contained the gene. (Even though we usually think of viruses are harmful, scientistshave found ways to use them in helpful wayslike to deliver genes to a monkeys eye!) Overthe next few weeks, the monkeys began to make the red-detecting protein. After about 20weeks of this gene therapy, the monkeys were making enough of the protein to be able to tellred from green.

Feasting time Digital simulations show what a squirrel monkey named Dalton mayhave seen before (left) and may now see after (right) gene therapy to correct hiscolor blindness.

Neitz Laboratory, University of Washington

To test the monkeys eyesight, Neitz and his team showed them a grid of dots, some of themcolored, some of them gray. If the monkeys pressed the colored dots, they received a treatgrape juice. Before the gene therapy, the monkeys could easily pick out blue or yellow dots,but they had a hard time telling red or green dots from gray dots or from each other. Afterreceiving the gene injections, Sam and Dalton were able to pick out all of the colors (and drinklots of grape juice).

Bevil Conway, a neuroscientist at Wellesley College in Massachusetts, says the experimentshows that seeing in full color only requires the addition of a gene for detecting certain colorsof light. Before the experiment, scientists were not sure whether the monkeys brains wouldknow how to handle new colorsbut the monkeys seemed to be able to see and understandthe new colors right away. Somehow the brains of these monkeys are already wired todecode these color signals, Conway says.

Neitzs experiment is good for Sam and Daltonbut what about the rest of the world? Theysay its too early to know if genetic therapy could ever be used to help colorblind people seecolors, or to help blind people see. Plus, it may be true that Sam and Dalton arent seeing redand green as we know themthey may just be seeing other shades of yellow and blue.

Nonetheless, the idea of giving color vision to a couple of monkeys is capturing the attentionof researchers who study vision. The achievement is technically amazing and conceptuallyvery cool, says Melissa Saenz, a scientist at Caltech in Pasadena, Calif.


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