Friday, August 24, 2007

Scientists simulate out-of-body experiences

"New virtual-reality experiments show the brain can be tricked into believing it's outside the body, lending credence to the strange claims of some patients and shedding light on how the brain might generate its "self-image."

“We have decades of intense research on visual perception, but not very much yet on body perception," said Henrik Ehrsson of University College London.

"But that may change, now [that] virtual reality offers a way to manipulate full-body perception more systematically and probe out-of-body experiences,” said Olaf Blanke, a Swiss Federal Institute of Technology neuroscientist.

The researchers worked on separate studies, which are detailed Thursday in the online edition of the journal Science.

Researchers equipped subjects with virtual-reality goggles that showed images from a stereoscopic video camera setup — two cameras spaced like a pair of eyes. When placed behind the person wearing the goggles, the cameras acted as a "virtual self" that looked at the subject's back.

As subjects watched themselves from behind, an experimenter prodded their chests with one hand while prodding the air just below the cameras at the same time. Because subjects could see the experimenter's hand but not the spot it was poking, researchers said subjects felt as if they were being poked in the chest — outside their bodies.

“This was a bizarre, fascinating experience for the participants," Ehrsson said. "It felt absolutely real for them and was not scary. Many of them giggled and said ‘Wow, this is so weird.’”

Where's my body?
But the researchers didn't stop there. They also performed the experiment with cameras behind a wigged mannequin to test the brain's limits of self-perception.

When they saw a bodily shape, they still felt it was them," said Bigna Lenggenhager, a psychologist also with the Swiss Federal Institute of Technology. She explained that touching both the fake body and the real body at the same time tricked many of the subjects.

"They felt a touch was there but couldn't pinpoint it," Lenggenhager said, noting that some felt as if the mannequin was their own body.

Going even further to test the effect, researchers removed subjects' goggles and asked them to move to where they believed they were standing during the experiment. Almost every time, she said, they overshot and walked back to their virtual self's location — and not where their real or simulated body was situated.

"They didn't localize themselves where their real body was," Lenggenhager told "Where the camera was is where they believed they were."

Monday, August 20, 2007

Sonic Boom!

A Sonic Boom
Credit: Ensign John Gay, USS Constellation, US Navy

Explanation: Is this what a sonic boom looks like? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.

Saturday, August 04, 2007

Apes play charades to communicate

"When humans play charades, the game's ban on talk often reduces players to wild gestures in a frustratingly minimalist form of communication. Still, skillful players get the point across eventually.

Apes can't talk at all, of course. But now scientists have found that orangutans rely on the same kinds of strategies seen in charades when they try and get their point across.

The finding hints at how the earliest forms of language might have developed among humanity's ancestors.

Ape the humans
Charades involves using only body language to act out a word or phrase that others must guess. When playing charades, people often repeat and hone gestures that have already worked and abandon ones that did not. This strategy not only improves a player's chances of picking effective gestures, but also gives hints to partners on how well or poorly they are doing.

To see how capable orangutans are of communicating with people via gestures, psychologists Erica Cartmill and Richard Byrne at the University of St. Andrews in Scotland presented six adult female orangutans in zoos a chance to essentially play charades.

The apes were shown one tempting food item, such as bananas or whole-grain bread, and one not-so-tempting food item, such as celery or leeks. The food could only be reached by signaling for human help, such as by pointing with fingers, blowing a "raspberry" or spitting through the bars.

At times, the researchers purposefully misunderstood the orangutans' requests. Sometimes they provided only half of the delicious treat, while other times they handed over the unsavory alternative instead.

When people pretended not to comprehend what the apes' aims were, the creatures relied on the same basic strategy people follow in playing charades.

"The orangutans made a clear distinction between total misunderstanding, when they tended to give up on the signals they'd used already and use new, but equivalent, ones to get the idea across, and partial misunderstanding, when they tended to repeat the signals that had already partially worked, keeping at it with vigor," Cartmill said. "The response showed that the orangutan had intended a particular result, anticipated getting it and kept trying until it got the result."

Byrne noted that "looking at the tapes of the animal's responses, you can easily work out whether the orangutan thinks it has been fully, partially or not understood."

"In effect, they are passing information back to the audience about how well they are doing in understanding them — hence our 'charades' analogy," Byrne added. He and Cartmill detailed their findings Aug. 2 in the journal Current Biology.

Eager to play
Cartmill noted that the term "experiment" has gained an undeserved association with invasive or artificial studies." "The individuals I tested treated the experiment as a sort of game and eagerly approached me as I set up the equipment, hoping to succeed in winning the banana this time," she said.

Primate psychologist Anne Russon at York University in Toronto said these findings add weight "to the view that great apes—probably all of them [including orangutans]—can communicate intentionally and can do so well beyond basic levels."

Russon noted orangutans play a very important role in understanding the evolution of advanced communication because they are the "oldest" of the great apes, having diverged as a distinct species far earlier than any of the African great apes—12 to 15 million years ago versus 4 to 8 million years ago.

These findings "therefore make it very likely that the mental abilities which support this sophisticated intentional communication evolved when the earliest great apes evolved, some 12 to 15 million years ago," Russon said. "That is, they place the origins of intentional communication well prior to human evolution."

Royal Aztec crypt wows archaeologists

Finding could be first tomb of ruler from this civilization ever discovered

"Mexican archaeologists using ground-penetrating radar have detected underground chambers they believe contain the remains of Emperor Ahuizotl, who ruled the Aztecs when Columbus landed in the New World. It would be the first tomb of an Aztec ruler ever found.

The find could provide an extraordinary window into Aztec civilization at its apogee. Ahuizotl (ah-WEE-zoh-tuhl), an empire-builder who extended the Aztecs’ reach as far as Guatemala, was the last emperor to complete his rule before the Spanish Conquest.

Accounts written by Spanish priests suggest the area was used by the Aztecs to cremate and bury their rulers. But no tomb of an Aztec ruler has ever been found, in part because the Spanish conquerors built their own city atop the Aztec’s ceremonial center, leaving behind colonial structures too historically valuable to remove for excavations.

One of those colonial buildings was so damaged in a 1985 earthquake that it had to be torn down, eventually giving experts their first chance to examine the site off Mexico City’s Zocalo plaza, between the Metropolitan Cathedral and the ruins of the Templo Mayor pyramid.

Archaeologists told The Associated Press that they have located what appears to be a six-foot-by-six-foot entryway into the tomb about 15 feet below ground. The passage is filled with water, rocks and mud, forcing workers to dig delicately while suspended from slings. Pumps work to keep the water level down.

“We are doing it very, very slowly ... because the responsibility is very great and we want to register everything,” said Leonardo Lopez Lujan, the lead government archaeologist on the project. “It’s a totally new situation for us, and we don’t know exactly what it will be like down there.”

As early as this fall, they hope to enter the inner chambers — a damp, low-ceilinged space — and discover the ashes of Ahuizotl, who was likely cremated on a funeral pyre in 1502.
By that time, Columbus had already landed in the New World. But the Aztecs’ first contact with Europeans came 17 years later, in 1519, when Hernan Cortes and his band of conquistadors marched into the Mexico Valley and took hostage Ahuizotl’s successor, his nephew Montezuma.

Ahuizotl’s son Cuauhtemoc (kwow-TAY-mock) took over from Montezuma and led the last resistance to the Spaniards in the battle for Mexico City in 1521. He was later taken prisoner and killed. Like Montezuma, his burial place is unknown.

Because no Aztec royal tomb has ever been found, the archaeologists are literally digging into the unknown. Radar indicates the tomb has up to four chambers, and scientists think they will find a constellation of elaborate offerings to the gods on the floor.

“He must have been buried with solemn ceremony and rich offerings, like vases, ornaments ... and certainly some objects he personally used,” said Luis Alberto Martos, director of archaeological studies at Mexico’s National Institute of Anthropology and History.

The tomb’s curse — water — may also be its blessing. Lopez Lujan said the constant temperature of the pH-neutral water in the flooded chambers, together with the lack of oxygen, discourages decomposition of materials like wood and bone that have been found at other digs around the pyramid, which was all but destroyed in the Conquest.

“This would be quite an important find for Aztec archaeology,” said Michael Smith, an archaeologist at Arizona State University who is not connected to the dig. “It would be tremendously important because it would be direct information about kingship, burial and the empire that is difficult to come by otherwise.”

All signs found so far point to Ahuizotl. The site lies directly below a huge, recently discovered stone monolith carved with a representation of Tlaltecuhtli (tlahl-tay-KOO-tlee), the Aztec god of the earth.

Depicted as a woman with huge claws and a stream of blood flowing into her mouth as she squats to give birth, Tlaltecuhtli was believed to devour the dead and then give them new life.

The god was so fearsome that Aztecs normally buried her depictions face down in the earth. However, this one is face-up.

In the claw of her right foot, the god holds a rabbit and 10 dots, indicating the date “10 Rabbit” — 1502, the year of Ahuizotl’s death.

“Our hypothesis is precisely that this is probably the tomb of Ahuizotl,” Lopez Lujan said."

Thursday, August 02, 2007