Why This Blurry Optical Illusion Disappears If You Stare at It

iStock
iStock

Optical illusions do weird things to our senses, like making us see or hear things that aren't really there. This illusion recently shared by Reddit user NightBreeze13 does something unique: Stare at it long enough and the image seems to disappear completely.

This is called Troxler fading or the Troxler effect, a phenomenon first identified by Ignaz Paul Vital Troxler in 1804. According to The Verge, it's what happens when we fix our eyes on an unchanging scene for a long-enough period of time. When sensory information is new our brain places a lot of importance on it. But if certain stimuli have been consistently hitting our senses for a while, like a dull toothache or the hum of a refrigerator, our brains have a way of tuning them out.

This is the case with the picture above. Choose a fixed spot in the image to stare at and allow at least a minute or so to pass. The colors should gradually fade from your vision, leaving a white square in its place.

So why does the effect work here, and not when you're staring out a window or at a painting? The blurriness helps: The smallest movements, whether they're from your eyes or the object of your gaze, feed you new sensory information, thus resetting the process. If your eyeballs wiggle slightly while staring at this image, your brain will have a harder time noticing it because it's already so blurry.

But having a steady gaze is still important. If you don't see anything happening after looking at the illusion for a minute, trying moving your cursor over the image and staring at that. Closing one eye can also help you keep the other eye as still as possible.

[h/t The Verge]

Being Surrounded By Greenery Can Be Good for Your Heart

iStock.com/Givaga
iStock.com/Givaga

Living in a place with a little greenery is good for your health in more ways than one. Recent research has found that people perceive their health status as significantly better if they live around trees, and for good reason—in addition to helping you chill out, exposure to lots of green vegetation may be good for your cardiovascular health, as Cardiovascular Business reports.

A new study in the Journal of the American Heart Association suggests that living in green areas is correlated with certain biomarkers for cardiovascular health. Scientists analyzed blood and urine samples from 408 people at a cardiology clinic, then compared the results to satellite-derived data on the levels of greenery around those patients’ homes (using 820-foot and half-mile radiuses).

Adjusting for age, sex, race, smoking status, “neighborhood deprivation” and other factors known to be linked heart disease rates, the researchers found that living in a green area was correlated with several markers of a healthy heart. Blood and urine samples from those participants who lived in green neighborhoods showed lower levels of sympathetic activation—the body’s automatic fight-or-flight response, which raises the heart rate and is involved in heart failure. Those participants also had reduced oxidative stress—an imbalance between free radicals and antioxidants in the body, which can cause tissue damage and is linked to chronic disease. And they had higher angiogenic capacity, which refers to the body’s ability to form new blood vessels.

All this suggests that being around trees is somehow linked to having a healthier heart, though these are just biomarkers, not rates of heart disease or major cardiac events. But while scientists have yet to prove directly that being around trees causes your heart to be healthier, it’s not the first study to suggest a link. In 2015, a study of American women found that rates of heart disease went up in certain areas after a beetle invasion killed off a significant number of trees. Other studies have suggested that being around trees can reduce stress, which in itself may affect your risk of heart disease. Luckily, whether it qualifies as heart medicine or not, spending more time hanging out under trees couldn’t hurt.

[h/t Cardiovascular Business]

14 Facts About Feet

iStock/pepifoto
iStock/pepifoto

The foot is one of the most overworked, under-appreciated parts of the human body. Think about it: In a single day, the average person takes 8000 to 10,000 steps. That works out to be four trips around the world over a lifetime, putting a lot of wear and tear on your intricate foot bones. The foot may be humble, but its design is essential to how we walk upright, and hoofing it on two feet is a defining feature of humanity. Here are some fun—and a few funky—facts about the human foot.

1. FOOT BONES MAKE UP ABOUT A QUARTER OF ALL THE BONES IN OUR BODIES.

There are 26 foot bones in each of your feet—one less than in each hand. When we’re born, those foot bones are mostly cartilage. They only completely harden around age 21.

2. HUMANS HAVE WORN SHOES FOR A VERY LONG TIME.

When did humans begin wearing shoes, anyway? About 40,000 years ago, according to research from Washington University in St. Louis that analyzed foot bones from Neanderthals and early humans. Older specimens had thicker, stronger toes, likely from gripping the ground as they walked barefoot. That’s around the same time that the archaeological record shows a burst of artistic and technological advancements among early humans, including the first stone tools, which may have aided in the production of shoes. The oldest preserved shoe, incidentally, is 5500 years old and was found in an Armenian cave, buried in sheep dung.

3. THE BIG TOE USED TO BE A KIND OF FOOT THUMB.

This grasping toe helped our predecessors climb trees and, when young, grip onto their mothers. Thanks to modern science, if you lose your thumb, you can now replace it with a toe: toe-to-thumb transplants are a surprisingly common procedure these days.

4. FOOT BONES HOLD BIG CLUES ABOUT THE EVOLUTION OF BIPEDALISM.

Scientists are studying Homo naledi, a specimen discovered in a South African cave in 2013 that many researchers believe is a new human relative. H. naledi had very human-like feet, but with somewhat curved toe bones that suggest it climbed trees. It could be that H. naledi was beginning to experiment with walking. 

5. THERE WAS A FOOT CHEESE EXHIBITION IN IRELAND.

Warm, sweaty feet make a perfect home for bacteria, which feed on our dead skin cells and produce gases and acids that emit those arresting foot odors. They're apparently also good at cultivating cheese. An exhibition in Dublin in 2013 displayed a variety of cheeses made with bacteria samples obtained from real people’s feet, armpits, and belly buttons. Delicious. (No one actually ate any of the cheeses.)

6. FEET ARE ONE OF THE MOST TICKLISH PARTS OF THE BODY.

There’s a good reason for that: Humans have nearly 8000 nerves in our feet and a large number of nerve endings near the skin. Having ticklish feet can be a good sign: Reduced sensitivity can be an indicator of peripheral neuropathy (numbness in the feet caused by nerve damage). 

7. FOOT NUMBNESS CAN CAUSE BIG PROBLEMS FOR DIABETICS.

Complications of diabetes include poor circulation and foot numbness that can lead to serious skin ulcers, which sometimes require amputation of toes or feet. In 2010 alone, 73,000 lower-limb amputations were performed on diabetics.

8. FOOT SIZES AND WIDTHS IN THE U.S. AND UK ARE INCREASING.

Feet are spreading to support extra weight as our populations pack on the pounds. According to a 2014 study by the College of Podiatry in the UK, the average foot has increased two sizes since the 1970s. As people have grown taller and heavier, feet respond by growing. It appears many people are still in denial about their expanding feet: Though retailers are starting to respond by making larger and roomier shoes, half of women and a third of men reported they buy poorly fitting shoes. Podiatrists say ill-fitting shoes are to blame for a significant portion of foot problems, especially among women.

9. MANY GLAMOROUS CELEBRITIES HAVE BIG FEET.

From the bound feet of female Chinese elites to Cinderella and Barbie, freakishly small feet are often celebrated as more feminine. But plenty of glamorous women both past and present have had larger than average feet, among them Jacqueline Kennedy, Oprah Winfrey, Uma Thurman, and Audrey Hepburn (size 10, 11, 11, and 10.5, respectively).

10. WOMEN HAVE FOUR TIMES AS MANY FOOT PROBLEMS AS MEN.

That painful fact is often attributed to wearing heels. Ironically, Western women started wearing heels to effect a more masculine look: European men adopted the look from Persian warriors in the 17th century, and women soon followed suit.

11. THE AVERAGE PERSON WALKS ABOUT 100,000 MILES IN A LIFETIME. 

That’s a lot of stress on our feet. It’s not surprising, then, that lower back pain, headaches, indigestion, and spine misalignment are often related to foot problems. Some runners blow way past this mark: They've logged at least 100,000 in running miles alone. One committed runner, Herb Fred, has run a whopping 247,142 miles.

12. FOOT SIZE HAS ZERO TO DO WITH PENIS SIZE.

In a study published in 2015, researchers synthesized data from 17 previous studies that included the penis measurements of more than 15,000 men from around the world. The results: There is little evidence that penis size is linked to height, body mass, or shoe size.

13. THERE'S A REASON GRANDPA'S TOENAILS LOOK LIKE THAT.

Ever heard someone describing their toenails as “horse hooves”? As we get older, our toenails tend to thicken, making them hard to trim. This happens because toenails grow more slowly as we age, causing the nail cells to accumulate. Stubbing toes, bad shoes, and dropping things on your feet can also cause thickening, as can fungal infections and peripheral arterial disease, which narrows arteries and reduces the blood flow to limbs.

14. THERE'S A GUINNESS WORLD RECORD FOR MOST FEET AND ARMPITS SNIFFED.

Odds are you don’t have any job-related tasks nearly as revolting as this one: In the 15 years that Madeline Albrecht worked for an Ohio lab that tests Dr. Scholl products, she sniffed more than 5600 feet and untold numbers of armpits. Albrecht currently holds the Guinness World Record for—yes, this is a category—the number of feet and armpits sniffed.

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