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

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.

Going Deeper:

The fish in the picture is alive and you’re looking inside its head. Really. It’s not a medical freak. Just a kind of fish with a naturally see-through forehead.

A new species, you might think. But no. The story is odder than that.

Meet one of the fish called barreleyes. This kind lives some 600 meters deep or more (that’s more than a third of a mile) in the Pacific Ocean.

A see-through forehead sounds like something you might remember to mention when describing a new fish. But 70 years ago scientists didn’t say a word about it when they gave the fish its official scientific name (Macropinna microstoma).

Those earlier fish scientists probably didn’t know about the clear forehead. They had to work from fish caught in deep nets and dragged up to the surface. The long trip up didn’t leave the samples in such good shape.

Today a scientist can send cameras and other equipment down to study deep-sea creatures where they live. Since 1993, cameras from the Monterey Bay Aquarium Research Institute in California have met these bizarre barreleyes three times in deep water off the coast.

And researchers managed to catch one and bring it to the surface in much better shape than usual.

What a difference meeting a live fish makes. Old reports had talked about some slime on the front of the fish. Now researchers see that the slime was probably the remains of the clear forehead.

The covering is tough and like the clear canopy on a fighter jet that lets the pilot see what’s happening, says Monterey Bay scientist Bruce Robison. In the fish, the rounded window is full of clear liquid and covers the eyes.

Like fighter pilots, these barreleye fish look out through their clear covering. Check the picture for the pair of fat, green domes like the tops of balls, inside the head. Those are the lenses of the fish’s eyes. (In the picture, the green lenses point up, and the fish is looking overhead.)

Each lens sits on top of a short, wide tube, which is the rest of the eye. That’s where the name barreleye came from, and that’s an odd shape for an eye. We hope this won’t happen, but if your eyeball fell out of your head, it would look like a ball. If it were All Planet Drop An Eyeball Day, there would be lots of balls. Cats, dogs, mice, elephants and lots of other animals have round eyes.

A front view of a type of barreleye shows its two nostril-like spots above the small mouth. The glow on the fish comes from the lights of a nearby camera vehicle. A glimmer of green inside the glowing clear forehead shows where the eye lenses are.

© 2006 MBARI

On barreleyes’ short tubes, the part that catches the image is at the bottom. That arrangement had puzzled scientists because tubular eyes should see only what’s straight in front of them and not much at the sides. That’s not very convenient. It would be a bit like looking at the world through the tube from a roll of toilet paper.

But looking at a living specimen, the researchers realized that an eye tube can move. Barreleyes point it upright to look overhead and then swing the lens downward so the tube points straight ahead, like the barrel of a mini cannon.

When the eyes point forward, the fish looks toward its pouty little mouth. Its lips stick out a bit, as if they would be good for picking morsels of food out of small places.

A siphonophore, a long string of filmy sea creatures, swims through the water (front end to the right) snagging food in its stinging tentacles. Researchers now wonder if the clear-headed barreleye fish steals food from siphonophores. The barreleye’s

© 2001 MBARI

What these barreleyes may do is steal food from creatures called siphonophores (sigh-FAH-nuh-4s), say the Monterey Bay scientists. Siphonophores in the area look like long, skinny, ultrafrizzy scarves made of bits of pale, soft film. Don’t wrap one around your neck though — they sting.

But the scientists think the barreleye might not care about the stings. Its clear forehead protects its eyes. So its mouth could nip off bits of prey that the siphonophores get tangled in their frizz. A clear forehead may actually be like fish goggles.

Power words: (loosely adapted from Yahoo! Kids Dictionary, which is also the American Heritage® Dictionary of the English Language, Fourth Edition)

canopy: a covering

lens: A clear part of the eye that bends the light passing through it so light rays hit the proper place for forming a picture.

siphonophores: sea creatures with clear, filmy bodies and stinging cells that band together in floating colonies. Famous example: the Portuguese man-of-war.

Going Deeper:

Scientists are developing “smart” lenses that sense where your eyes are looking and automatically focus to help you see more clearly.

Electric signals from microchips in the black boxes attached to these experimental eyeglasses change the focus setting to improve vision.

Guoqiang Li et al./Proceedings of the National Academy of Sciences

The main market for the glasses is adults older than 45—perhaps your parents or grandparents. At this point in life, most people start to get worse at seeing things that are close to them, such as books and computer screens.

When the decline begins, people usually start wearing reading glasses. Or, they get bifocals, which have divided lenses—a top part for seeing far and a bottom part for seeing near. Some kids with vision problems have to wear such glasses, too.

University researchers are working with a company called PixelOptics, in Roanoke, Va., to replace bifocals with electric lenses that can switch quickly from one type of focus to another.

“You don’t have just the bottom half of your eyeglasses” for close vision, says electrical engineer David L. Mathine of the University of Arizona in Tucson. He’s one of the inventors. “You get the whole view,” he says.

Each lens is made from two layers, and each layer is made up of two sheets of glass, with a thin layer of fluid sandwiched between the sheets. The fluid contains a transparent type of material called a liquid crystal, which is made of molecules that are shaped like rods. To change a lens’ focus, scientists apply electricity to the inner surface of one of the glass sheets in each layer.

In response to the electricity, the crystal rods rotate. Their direction determines how quickly light passes through the liquid-crystal layer. The process allows the material to focus light so that a crisp image forms inside the viewer’s eyes.

An image is out of focus when a special, electrically controlled lens is off (left) but clear when the lens is on (right).

Guoqiang Li et al./Proceedings of the National Academy of Sciences

Scientists had made similar, electrically controlled lenses before, but these earlier lenses couldn’t focus well enough or change focus quickly enough to be useful in eyeglasses, the inventors say.

PixelOptics has announced that it also plans to make a version of the glasses that will help people achieve extrasharp vision—even better than normal 20/20 eyesight.—E. Sohn

Going Deeper:

Weiss, Peter. 2006. Switch-a-vision: Electric spectacles could aid aging eyes. Science News 169(April 22):243-244. Available at http://www.sciencenews.org/articles/20060422/fob2.asp .

You can learn more about smart glasses at www.gravitysedge.com/pixeloptics/ (PixelOptics).