One day you might not have to ask someone to lend a helping hand–because you’ll have a third arm of your own. At least, that’s a possible application of a mental trick scientists performed on 154 healthy volunteers: These men and women were made to feel as if they had three arms.

To pull off this ruse, the researchers placed a prosthetic arm next to a volunteer’s two real arms, and they touched the subject’s right hand and the rubber hand in exactly the same place at the same time. Because the taps were synchronized, the volunteer’s brain was tricked into feeling them both. According to Science Daily:

“What happens then is that a conflict arises in the brain concerning which of the right hands belongs to the participant’s body,” says Arvid Guterstam, one of the scientists behind the study. “What one could expect is that only one of the hands is experienced as one’s own, presumably the real arm. But what we found, surprisingly, is that the brain solves this conflict by accepting both right hands as part of the body image, and the subjects experience having an extra third arm.”

To prove that the test subjects really were having three-arm experiences, the scientists threatened both the fake and real hands with a knife, and determined that the subjects’ palms sweated the same amount in both circumstances. In other words, they had the same stress levels regardless of whether a real hand or the prosthetic was in danger.

As for applications, the researchers surmise that similar techniques could help someone paralyzed on one side to gain a feeling of ownership over a prosthetic. “It is also conceivable that people with demanding work situations could benefit of an extra arm, such as firemen during rescue operations, or paramedics in the field,” the study’s leader, Henrik Ehrsson, told Science Daily. Hey, what about the rest of us?

See Ed Yong’s post on Not Exactly Rocket Science for more details…

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80beats: Virtual Reality Gives Out-of-Body-and-Into-Someone-Else’s Experience
80beats: DARPA’s Next Prosthetic Arm Will Connect to Your Brain
Not Exactly Rocket Science: The Quantum Leap effect – creating a body-swapping illusion

Image: Guterstam et al.

Today, West Vancouver officials will roll out a new way to keep drivers alert and slow them down: a little girl speed bump. A trompe-l’œil, the apparently 3D girl located near the École Pauline Johnson Elementary School is actually a 2D pavement painting, similar to the one shown here.

In what sounds like a terrifying experience, the girl’s elongated form appears to rise from the ground as cars approach, reaching 3D realism at around 100 feet, and then returning to 2D distortion once cars pass that ideal viewing distance. Its designers created the image to give drivers who travel at the street’s recommended 18 miles per hour (30 km per hour) enough time to stop before hitting Pavement Patty–acknowledging the spectacle before they continue to safely roll over her.

The illusion is part of a $15,000 safety program that will run this week, led by the BCAA Traffic Safety Foundation and the public awareness group Preventable.ca. As drivers approach, the police will monitor the fake girl’s effects. Despite fears that drivers may stop suddenly or swerve into actual 3D children, David Duane of the BCAA Traffic Safety Foundation told CTV news that the bump was meant to bring attention to driver-caused pedestrian injuries, and that the fake girl should not cause accidents:

“It’s a static image. If a driver can’t respond to this appropriately, that person shouldn’t be driving….”

In 2008, Philadelphia used similar, virtual speed bumps–more common in Europe–in its “Drive CarePhilly” campaign. Philadelphia, however, chose a less anthropomorphic route–opting for three spikes.

UPDATE: Preventable.ca answers some questions about the experiment in a new blog post.

Route:
Discoblog: For the Driver Who Has Everything: An Augmented Reality Windshield From GM
Discoblog: Texting-While-Driving Coach Slightly Delays Appalling Crashes
Discoblog: Confused (and Injured) Pedestrian Sues Google Maps Over Bad Directions
Discoblog: AD4HERE: Digital License Plate Ads May Come to California

Image: Handout/Preventable.ca via PhysOrg.com

Remember those high school liquid nitrogen demonstrations? You know, the one where your teacher dipped a banana into the cloudy stuff, pulled it out, and then shattered it on the floor?

Well, Popular Science blogger Theodore Gray recently decided to stick in his hand. As you can see in a video over on their site, his hand survived the encounter. Though he stressed, and we reiterate, that this really isn’t a good idea unless you know what you’re doing, or unless you want your friends to call you Captain Hook, sticking your hand in the cold stuff isn’t necessarily a recipe for digit removal.

Since Gray’s hand was much warmer than the liquid nitrogen (which checks in at around negative 320 degrees Fahrenheit), the hand instantly created a layer of evaporated nitrogen gas–which shielded his skin, temporarily, from frostbite. Gray says on his blog:

“The phenomenon is called the Leidenfrost effect (after Johann Gottlob Leidenfrost, the doctor who first studied it in 1756). I’d known about it for years, but when it came time to test it in real life, I have to admit that I used my left hand, the one I’d miss less.”

For more videos of people doing questionable things in the name of science, check out DISCOVER’s new show Joe Genius.

Related content:
JOE GENIUS: Chemistry Cafe
Discoblog: Crazy Optical Illusion of the Day
Discoblog: To Levitate Water, Turn on the Strobe Lights
Discoblog: Prepare to Be Amazed… An iPhone App That Can Read Minds!

Image: flickr / Lee Gillen

It’s Science vs. Magic week at L.A.’s Magic Castle, where comic magician Rudy Coby and his friends have taken over the Victorian mansion-styled club, and where waitresses are sporting lab coats and serving drinks in test tubes.

Coby is reprising his mad scientist alter-ego Labman after a 15-year hiatus–during which time he crafted stage shows for one-time roommate goth rocker Marilyn Manson, who threatens a surprise cameo as “The Evil Magician” at one of Coby’s performances.

The event is an ode to magic’s time-honored and gleeful distortion of scientific and technological principals. Coby’s Hypnotron 2000 makes it look like your skin moves after staring at a spinning wheel. Andrew Mayne–who creates illusions for David Blaine and Penn & Teller, and also produced the G4 Network’s quirky G4 Underground–unveils a don’t-try-this-at-home effect that has him drinking –320 Fahrenheit liquid nitrogen.

College favorite Brian Brushwood has audience members use cell phones to capture a ghostly image on TV static patterns that their eyes miss (pictured). For the kids this weekend, mad scientist Prof. Wes Weasely wields audio magic with his theremin.

More surprise guests are planned Thursday through Sunday.

– by Sue Karlin

Related Content:
Discoblog: Crazy Optical Illusion of the Day
Discoblog: To Levitate Water, Turn on the Strobe Lights
Discoblog: Prepare to Be Amazed… An iPhone App That Can Read Minds!
DISCOVER: The Mathematics of… Shuffling

A few diamond cut-outs and a video camera are all the ingredients for one pretty awesome optical illusion, courtesy of GreeenPro2009.

That’s all we’re going to say. Enjoy.

How does it work? A few viewers offer their suggestions in the comments over on YouTube. (Hint: are those diamonds colored in solid gray tones?) What do you think?

Related Content:
Discoblog: To Levitate Water, Turn on the Strobe Lights
Discoblog: New Vibrating Jacket Lets Moviegoers “Feel” the Action
Discoblog: Prepare to Be Amazed… An iPhone App That Can Read Minds!

Video: YouTube / GreeenPro2009

The same technology that makes ravers at a club look like they’re gyrating in slow motion can be used to levitate water. Watch it here!

It’s a nifty illusion created by strobe lights, or a stroboscope, a device that emits quick pulses of light. In the setup shown in the video, all the water drops are actually falling and most of the time they are invisible. The drops are only visible during the millisecond pulses of the strobe light. By adjusting these pulses to the rate of the falling drops, the drops can be made to look like they are traveling at certain speeds, hovering in midair, or even levitating. Your mind automatically connects the images illuminated by the pulses, likes frames of an animated cartoon, creating the illusion of gravity-defying motion. What you perceive as a rising drop of water is actually frames of many different falling drops. The same concept is behind the wagon-wheel effect often seen in movies.

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