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The (kids') eyes have it
In a new study of visual abilities, researchers asked volunteers to identify the biggest orange circle. Here, each orange circle on the right is a little bit larger than the one on the left. Misleading images usually fooled adults but not children, while helpful images greatly aided adults but not kids.
Can you believe your eyes? A recent experiment suggests that the answer to that question may depend on your age.
In the experiment, kids and adults were asked to look at the same visual illusion — a picture that was designed to trick the viewer. The researchers who ran the experiment say that adults were more easily fooled by the illusion, and that the kids, especially those younger than age 7, saw the picture more accurately.
Martin Doherty, a psychologist at the University of Stirling in Scotland, led the team of scientists. A psychologist is a scientist who studies behavior and processes in the brain and may offer counseling to patients. Doherty says that his experiment can tell scientists something about how the human brain develops. In particular, the experiment shows that what 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 things around it. A baseball may look large when next to a golf ball, for example, but appear small when next to a basketball.
In this experiment, Doherty and his team tested the perception of the participants using pictures of solid orange circles. The researchers showed the same pictures to two groups of people. The first group included 151 children ages 4 to 10, and the second group included 24 adults of ages 18 to 25.
The first group of pictures showed two circles alone on a white background. One of the circles was 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 circle 95 percent of the time.
Next, both groups were shown a picture where the orange circles, again of different sizes, were surrounded by gray circles. Here’s where the illusion came in — remember the baseballs, golf balls and basketballs.
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 was surrounded by even smaller gray circles — making the orange circle appear larger than the other 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 smaller orange circle.
When young children ages 4 to 6 looked at these tricky pictures, they weren’t fooled — they were still able to find the bigger circle with roughly the same accuracy as before. Older children and adults, on the other hand, did not do as well. Older children often identified the smaller 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 did as 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 gray circles, as well as the orange circle in the middle. As a result, they’re more likely to fall for this kind of visual trick.
Doherty is not the first scientist to study visual context in children, and earlier studies have found that children, just like adults, can be fooled by illusion. Carl Granrud is a psychologist at the University of Northern Colorado in Greeley. He told Science News that Doherty’s findings seem sound, but that they were “somewhat surprising.” He pointed out that in other visual illusion tests, children were fooled, suggesting they had developed the ability to see visual context.
This experiment shows that sometimes, in order to get a sneak peek inside the brain, you have to try to trick it — and see what happens.
POWER WORDS (from the Yahoo! Kids Dictionary)
psychology The science that deals with mental processes and with behavior
optical illusion An image seen with the eyes that is deceptive or misleading.
perceive To become aware of directly through any of the senses, especially through sight or hearing.
context The part of an image that surrounds a particular part of the image and determines its meaning.
برچسب ها : The (kids') eyes have it ,
What the appendix is good for
It was a Saturday morning in 1991 when 12-year old Heather Smith woke up feeling nauseous. Spring break was just beginning, and her parents were planning to take her skiing the next day in Flagstaff, Ariz. — two hours from their home in Tempe.
A stomachache was not how Smith wanted to start vacation. “I was hoping I would get better,” she says, “So I could go ski.”
As the day progressed, things worsened. A sharp pain developed in her lower right side. She couldn’t swallow the soup her sister warmed up for her at lunchtime. By the time she saw a doctor later that afternoon, she was hunched over in pain.
When she learned that her appendix was infected, she didn’t have much time to be afraid. She was rushed into surgery. The next morning, her appendix was gone.
“It was a little scary because it happened so quickly,” says Smith, now an evolutionary biologist at the Arizona College of Osteopathic Medicine at Midwestern University in Glendale, Ariz. But she has never missed her long-lost organ. In fact, the emergency left her with a lifelong fascination for a body part she no longer has.
“I have always been interested in the appendix and trying to figure out why we have one,” Smith says. “There’s been this idea for so long that it didn’t do anything.”
Appendices have long been considered “vestigial structures.” That means we don’t actually need them. The brain, heart, skin and most other organs are essential for survival. But you can live a long life without an appendix. The same goes for tonsils, wisdom teeth, body hair and other vestigial structures.
At best, according to traditional thinking, vestigial structures just take up space. At worst, they can get infected and cause all sorts of trouble. So why do we have these unnecessary body parts in the first place?
Growing evidence suggests that we have them because they aren’t actually unnecessary at all. Their function probably depends on where you live (and perhaps when you lived). In some parts of the world, people still need vestigial body parts. Studying where and when these features are or were useful is helping scientists make new advances in modern medicine. The work is also providing insight into the history of humankind — telling scientists things about our ancestors that we didn’t know before.
“It may be the case with a lot of unnecessary body parts that they may have had a function in the past but we don’t necessarily need that function anymore,” says Smith, who ended up studying the appendix sort of by accident. “That can give us insights.”The hidden point
The appendix is a small organ that looks like a little worm (lower left of image). It doesn't lead anywhere, but may serve as a haven for good bacteria.
Consider your body, and you’ll notice a hodgepodge of random features that might seem silly when you stop to think about them. What’s the point of fingernails, for example? Why is there hair on your toes? And what’s the deal with muscles in your ears? Do we really need muscles in our ears?
Throughout history, scientists, too, have wondered about structures that don’t seem to do anything useful. The appendix is a popular example. This little, worm-like pouch is about four inches long and less than half an inch wide.
The organ grows near where the long intestine meets the short intestine. The intestines are essential for digestion, but the appendix appears to just sit there.
“It’s a dead-end sack,” says William Parker, an immunologist at Duke University in Durham, N.C. “It doesn’t go anywhere.”
Parker didn’t start out intending to study the appendix. His specialty is the immune system — a collection of organs, cells and molecules that our bodies use to stay healthy. But his research led him to the appendix anyway.
Parker knew that the human body is full of tiny organisms called bacteria, which can overwhelm the immune system, cause infections and make a person sick. He also knew that some bacteria are good for human health. Among other benefits, these “good” bacteria help people digest food and fight off “bad” bacteria that cause disease.
The immune system doesn’t just benefit from good bacteria, though. In the 1990s, Parker and colleagues began to figure out that the immune system also helps good bacteria flourish. These bacteria appear in thin layers called biofilms, which grow on the side of the gut near and inside the appendix. These biofilms, the researchers learned, provide a barrier that keep out bad bacteria.
“Once we figured that out, it should have been obvious to us what the appendix did,” says Parker, whose team also found that the appendix has a particularly robust biofilm. “It’s in the perfect spot to harbor bacteria — out of the flow and with a thin, narrow opening. And there’s a large amount of immune tissue associated with it.”
After stumbling on a possible link between the immune system and the appendix, though, the scientists still had some clues to compile before being sure of the organ’s purpose.Hangout for good bacteria
In 2007, Parker’s team put together all the evidence they had gathered and came up with a conclusion: The appendix serves as a “safe house,” Parker says, a storage bin for good bacteria. If bad bacteria attack, good bacteria emerge from the appendix and come to the rescue.
Having a safe space for good bacteria should be especially useful in parts of the world that are poor and undeveloped — places where people are starving, medicine is hard to come by, clean water is scarce and diarrhea can kill. In those places, Parker says, the appendix probably helps keep people alive, especially young children.
In fact, people in the developing world rarely get infected appendixes, like Smith’s. Most cases of appendicitis, in fact, occur in the United States and other developed countries, where water is purified, hospitals are sterilized and medical care is easier to get.
Those trends suggest that the appendix evolved in our ancestors to maintain health in a bacteria-filled world. Today, places such as the United States might be too sterile for the appendix. When the organ has nothing do, the immune system can turn on itself, sending people to the emergency room, Parker says. Other problems, such as allergies and immune diseases, might have similar roots.
Even in ultra-clean societies, then, the appendix and other vestigial organs might be unrecognized heroes.
“Just because body parts don’t seem to have any usefulness here doesn’t mean you wouldn’t need them if you were suddenly thrown in the middle of the woods somewhere and had to drink from whatever mud hole you could find nearby and you had to run away from predators,” Parker says. “Problems we are having today with allergies and autoimmune diseases are a result of the body not really fitting in with our culture.”
Figuring out the true purpose of the appendix and other overlooked organs, Parker adds, is an important step toward solving medical mysteries.
“We want to understand how the body functions so we can work towards getting it to function normally,” he says.
To do that, it can help to take an historical view. By considering what was normal a long time ago and comparing the old normal to the new normal, researchers can see how evolution has shaped our bodies over hundreds of thousands of years. That process of change over time is called evolution.
“The best way to figure out how the body was designed to work,” Parker says, “is to look at how it was meant to work over hundreds of millions of years of evolution.”Wise beyond our years
The appendix isn’t the only example of a body part with hidden powers. Wisdom teeth are another. This final set of molars usually grows in at around age 20. Today, most people get their wisdom teeth removed before the bulky molars can squeeze other teeth out of place or get infected.
Millions of years ago, though, human faces weren’t as flat as they are today and mouths had more room for wisdom teeth. After 20 years of life without dental care, our ancestors would have benefited from a fresh set of strong teeth that could chew and grind raw food.
Our ancestors may have found wisdom teeth more useful than we do.
As for other structures long thought to be pointless, a recent study found that the spleen stores a whole lot of immune cells. Among other roles, those cells help to repair hearts that are damaged. Tonsils, which are also removed routinely in many developed countries, probably help boost the immune system, as well, Parker says.
As they continue to find purposes for seemingly purposeless body parts, scientists are connecting our present with the past. They are also connecting the human animal with other animals on Earth.
Last year, Smith teamed up with Parker and other colleagues to look at a whole bunch of mammal species, some that lived tens of millions of years ago. The researchers found that the appendix has existed in a wide range of animals, from rodents to primates to Australian marsupials. The study also revealed that the appendix evolved more than once throughout history. Both findings suggest that the appendix has had an important purpose throughout time.
By looking closely at our body’s “pointless” parts, we can begin to imagine what our bodies used to be able to do. Recognizing the body’s lingering power could also open up a whole new future of possibilities.
“Our evolution gives our bodies a lot of resilience and strength we really don’t need very much in our society,” says Parker. “I sit around in my office and have all the food I want. My body can do so many things I never ask it to do.”
This story and other Science News for Kids features describing research in medicine and biology are supported with funding from The Lasker Foundation. The foundation and its programs are dedicated to the support of biomedical research toward conquering disease, improving human health and extending life.
برچسب ها : What the appendix is good for ,
Slumber by the numbers
Scientists hope to understand why most teenagers don’t get enough sleep at night, and how too little sleep affects their well-being.
It’s an important question: “On an average school night, how many hours of sleep do you get?”
More than 12,000 high school students were recently asked that during a survey by the Centers for Disease Control and Prevention. The overall answer: not enough.
Studies have shown that teenagers really need at least nine hours of sleep, with eight hours considered a “borderline” acceptable amount. In the CDC study, however, only around 900 of the surveyed students reported getting the ideal amount, while an additional 2,800 reported averaging eight hours of shut-eye nightly.
Danice Eaton, a research scientist at the CDC, led this most recent survey, which was part of what the agency calls a Youth Risk Behavior Surveillance. Every year, CDC scientists like Eaton ask high school students about behaviors that can harm their health. The questions are on topics such as nutrition, weapons, sex and drug use — and sleep.
Sleeplessness, like other behaviors, carries a heavy toll. Scientists ask the survey questions to find a way to help people. Among people between the ages of 10 and 24, nearly three of every four deaths happen for one of the following reasons: motor vehicle accident, other accidents, homicide and suicide. Scientists like the CDC’s Eaton hope that by understanding the risky behaviors, like sleeplessness, that might contribute to these tragedies, they may be able to save lives.
Also, without enough sleep, a person might have more trouble learning or exercising good judgment. Over time, people who regularly don’t get enough sleep are more likely to be obese (which means very overweight) or get sick with serious diseases, some studies have found. Other studies have shown that even one night with less sleep than needed can throw off the chemical balance of the body.
Most students interviewed got much less than eight hours of sleep. Eaton and her team found that 30.2 percent, or about 3,600 students, sleep for only seven hours per night. About 2,700 students, or 22.8 percent, sleep only six hours per night. About 1,200 students, or 10 percent, reported sleeping five hours, and 5.9 percent, or 708 students, said they slept four hours or less.
The CDC’s study identified a problem — but not the cause. Why do teenagers sleep less than they should? Maybe many teens like to work and stay up late. (This can make it rough to get up for school the next morning.) A number of scientific studies suggest some other ideas, as well. Computer use may be a culprit: Some scientists have found that the blue light given off by computer screens may interfere with the body’s internal biological clock — making it difficult to go to sleep.
Other scientists have come up with new and interesting ways to help people who can’t sleep.
Studies suggest, for example, that a person’s biological clock responds favorably to blue light that is the color of the sky. So perhaps people are biologically “set” to start their day when they see the sky — and when people see a blue computer screen, their bodies misinterpret the light as morning. Some research has shown that donning a pair of yellow glasses at night will block the blue wavelengths. This allows people to become naturally sleepy, even after a long night on the computer.
Whatever the cause of too little sleep may turn out to be, the CDC’s effort to identify the problem is an early step toward finding a treatment. Once scientists understand the problem, they can design ways to solve it.
برچسب ها : Slumber by the numbers ,