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Why Are Our Brains Susceptible to Body Illusions?

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Are you bored with your body? Is bilateral symmetry feeling a little stale?

You’re in luck. You don’t need cyborg technology to give yourself an upgrade. Just grab a buddy, a towel, and a rubber hand. Line up your real hands and the fake hand on a table. Drape the towel over one arm and the rubber wrist so that it looks like you have two arms growing out of one shoulder. Then ask your friend to poke the hand on your mutant side with synchronized, unpredictable movements. As you watch, you will suddenly feel as if the rubber hand is your own.

Intrigued? You’re not alone. When a variant of the Third Hand Trick was discovered in the nineties, other psychologists jumped into the illusion game.

For inspiration, they turned to the classic Pinocchio Effect. By standing behind a friend and applying random, synched touches to the tip of your and your partner’s noses, you make it seem that you have sensation in your friend’s nose. When confronted with this bizarre scenario, your brain concludes that your nose must have stretched three feet. From there, things got Frankensteinian.

Using only a mirror, Dr. V. S. Ramachandran started resurrecting the lost limbs of amputees, thus relieving their excruciating phantom pain.

And Henrik Ehrsson began erasing the boundaries of the self. Using cameras, video goggles, and the synchronized poking technique of the Third Hand Illusion, you can now inhabit a mannequin, doll, or 30-foot dummy.

Not impressed? He can even strip you of your body entirely. Strap on some video goggles and position a camera behind you. While you stare at the back of your own head, have your some friends poke your chest and the camera’s stand in time. Soon, you’ll zip backwards out of your meat sack.

But how? How can a few seconds of trickery rewrite your body schema? It’s because you don’t have a fixed schema. Your brain is making it up as you go along. You perceive the world with two tools—bottom-up and top-down processing. Bottom-up processing starts with your senses and builds understanding from there. (Look, something white and round. Oh, it’s your mug.) Top-down processing applies assumptions to the environment. (Your mug is always on your desk, so that thing by your elbow must be your mug.)

You usually experience your body with top-down processing. There’s no reason to continually check that you haven’t sprouted a new hand. But body illusions challenge your assumptions. When the synchronicity of the poking makes it seem that you have nerves somewhere they don’t belong (a rubber hand, a friend’s nose, a reflection, a mannequin, a camera stand, etc), your bottom-up processing kicks into gear. It thinks, “If it has your nerves, it must be part of you!” Your top-down and bottom-up processes battle it out, and in most cases, bottom-up processing wins. But, really, you win.

Because if you ever do acquire a third hand, your brain will be ready.

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Why Does the Queen Have Two Birthdays?
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CHRIS JACKSON, AFP/Getty Images

On April 21, Her Majesty Queen Elizabeth II will turn 92 years old. To mark the occasion, there are usually a series of gun salutes around London: a 41 gun salute in Hyde Park, a 21 gun salute in Windsor Great Park, and a 62 gun salute at the Tower of London. For the most part, the monarch celebrates her big day privately. But on June 9, 2018, Her Majesty will parade through London as part of an opulent birthday celebration known as Trooping the Colour.

Queen Elizabeth, like many British monarchs before her, has two birthdays: the actual anniversary of the day she was born, and a separate day that is labeled her "official" birthday (usually the second Saturday in June). Why? Because April 21 is usually too cold for a proper parade.

The tradition started in 1748, with King George II, who had the misfortune of being born in chilly November. Rather than have his subjects risk catching colds, he combined his birthday celebration with the Trooping the Colour.

The parade itself had been part of British culture for almost a century by that time. At first it was strictly a military event, at which regiments displayed their flags—or "colours"—so that soldiers could familiarize themselves. But George was known as a formidable general after having led troops at the Battle of Dettingen in 1743, so the military celebration seemed a fitting occasion onto which to graft his warm-weather birthday. Edward VII, who also had a November birthday, was the first to standardize the June Trooping the Colour and launched a tradition of a monarchical review of the troops that drew crowds of onlookers.

Even now, the date of the "official" birthday varies year to year. For the first seven years of her reign, Elizabeth II held her official birthday on a Thursday but has since switched over to Saturdays. And while the date is tied to the Trooping the Colour in the UK, Commonwealth nations around the world have their own criteria, which generally involve recognizing it as a public holiday.

Australia started recognizing an official birthday back in 1788, and all the provinces (save one) observe the Queen's Birthday on the second Monday in June, with Western Australia holding its celebrations on the last Monday of September or the first Monday of October.

In Canada, the official birthday has been set to align with the actual birth date of Queen Victoria—May 24, 1819—since 1845, and as such they celebrate so-called Victoria Day on May 24 or the Monday before.

In New Zealand, it's the first Monday in June, and in the Falkland Islands the actual day of the Queen's birth is celebrated publicly.

All in all, just another reason it's great to be Queen.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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What Is the Meaning Behind "420"?
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Whether or not you’re a marijuana enthusiast, you’re probably aware that today is an unofficial holiday for those who are. April 20—4/20—is a day when pot smokers around the world come together to, well, smoke pot. Others use the day to push for legalization, holding marches and rallies.

But why the code 420? There are a lot of theories as to why that particular number was chosen, but most of them are wrong. You may have heard that 420 is police code for possession, or maybe it’s the penal code for marijuana use. Both are false. There is a California Senate Bill 420 that refers to the use of medical marijuana, but the bill was named for the code, not the other way around.

As far as anyone can tell, the phrase started with a bunch of high school students. Back in 1971, a group of kids at San Rafael High School in San Rafael, California, got in the habit of meeting at 4:20 to smoke after school. When they’d see each other in the hallways during the day, their shorthand was “420 Louis,” meaning, “Let’s meet at the Louis Pasteur statue at 4:20 to smoke.”

Somehow, the phrase caught on—and when the Grateful Dead eventually picked it up, "420" spread through the greater community like wildfire. What began as a silly code passed between classes is now a worldwide event for smokers and legalization activists everywhere—not a bad accomplishment for a bunch of high school stoners.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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