- Copycats Prevail in Computer Survival Game
- Venus Orbiter Finds Potential Active Volcanoes
- Impressive New Hubble Image of Odd Galaxy Triplet
Posted: 08 Apr 2010 01:08 PM PDT
Being a maverick doesn't pay, at least not when braving a strange new world in a computer game that's like Survivor meets Second Life. The outcome of a computerized game tournament, which finds that a copycat strategy is best, may help explain why mimicking others is so prevalent in nature.
"What we find is that under a very broad range of circumstances, not only does social learning beat asocial learning hands down, it annihilates it," says study coauthor Kevin Laland of the University of St. Andrews in Scotland. "There's no balance, no mix of asocial and social learning."
Laland and his colleagues set up a tournament in which participants wrote computer programs that controlled the behavior of avatars living in a strange and unpredictable world. The competition pitted 104 teams against each other to see who could come up with the best survival strategy and encode it in a computer program.
"In a way, it's a bit like being dumped on a Pacific island where you don't know anything about the environment," says Laland. "You don't know what's good to eat. You could fish, you could catch crabs, you could hunt antelope, pick for tubers, you name it. Some of these will reap rich rewards and some will be fruitless."
Going into the study, the researchers thought the optimal strategy would be some kind of mixture of copying and innovating, Laland says, both of which have drawbacks. An unknown berry might turn out to be a great food source for the person who first discovers it, or the berry might be poisonous. On the other hand, copying others might be safer, but not if the information is outdated or wrong. To the researchers' surprise, the best method relied almost exclusively on copying.
Players were presented with a choice of 100 different moves, each with its own payoff. Each move, although described purely in mathematical terms, could be thought of as a corollary of picking berries or hunting antelope. To make the situation more like reality, the payoffs associated with each action changed with time, representing a shifting environment. At every turn, the players could copy others' behaviors or write a program to create a new move. As the players racked up bigger payoffs, the probability that the avatar reproduced increased — a sign of success.
After many iterations of the tournament, a program called discountmachine written by a team of two graduate students from Queen's University in Canada beat out the competition. Mathematician Daniel Cownden and neuroscientist Timothy Lillicrap won 10,000 pounds for the winning program.
In addition to discountmachine's penchant for copying, the program relied on a feature called a neural net that tracked how fast the environment was changing. This allowed avatars to pay less attention to previous actions that were once successful, but may have become outdated.
"The results have influenced my own thinking about how people can learn from their own experience and the experience of others," comments Robert Axelrod of the University of Michigan in Ann Arbor. In the 1980s, Axelrod conducted a similar tournament to study cooperation.
There is a caveat to the winning program's success, though. It works only when there are other agents around to copy. "They're effectively kind of parasitic," Laland says. "You can think of social learners as information scroungers — they're stealing the information produced by others."
Evolutionary ecologist Richard McElreath of the University of California, Davis calls the new study a "valuable and unique contribution," but points out that the current tournament defines social learning differently from previous studies and so may not be at odds with earlier models of behavior. Even so, McElreath suspects that this tournament will "become a classic."
Posted: 08 Apr 2010 12:49 PM PDT
The Venus Express spacecraft has found convincing evidence that Earth is not the only geologically active planet in the solar system.
Infrared emissions from lava flows on the surface of Venus indicate that they are relatively young, which means the planet may still be capable of volcanic eruptions.
"The solidified lava flows, which radiate heat from the surface, seem hardly weathered. So we can conclude that they are younger than 2.5 million years old — and the majority are probably younger than 250,000 years," Jörn Helbert of the DLR Institute of Planetary Research in Germany, co-author of a study published April 8 in Science, said in a press release. "In geological terms, this means that they are practically from the present day."
The results could explain why there are fewer asteroid impacts than expected on the planet's surface. Volcanism has been the prime suspect, because lava flows can fill in and obscure craters. But scientists were unsure whether a major episode of volcanic activity resurfaced much of the planet all at once in the past, or if intermittent activity has slowly filled in craters over time. The existence of a recent flow suggests the latter is more likely, and that volcanism may be ongoing.
Venus is shrouded in a thick cloud cover which obscures the visible light emissions form the surface. So a team led by Suzanne Smrekar of NASA's Jet Propulsion Laboratory studied the thermal emissions of the surface using the Visible and Infrared Thermal Imaging Spectrometer on the Venus Express orbiter. Older surfaces tend to be smoothed by weathering over time, while younger surfaces are more rough and have higher thermal emissions.
Several areas on the surface had been identified as potential volcanic centers by radar imagery data from the Magellan mission, which ended in 1994 when the spacecraft was intentionally crashed into the surface. Smrekar's team targeted three of these areas and found they had higher thermal emissions than the surrounding areas.
"Now we have strong evidence right at the surface for recent eruptions," Smrekar said in a press release.
Because Venus is similar in size and internal structure to Earth, comparisons between the two planets can help scientists understand our own planet's evolution. If volcanism on Venus is also similar to Earth, as the new study indicates, that narrows the factors that could have sent the planets on such different paths that ended with Earth being habitable and Venus being bone dry and hellishly hot.
In order to determine what the young rock is made of, Helbert plans to build a lab that can heat various rock types to around 900 degrees Fahrenheit, the planet's surface temperature, and study their thermal emission signatures to compare to the Venus Express readings.
Images: 1) 3-D radar image of Maat Mons volcano./DLR. 2) Thermal emission signature of Venutian volcano. Red is higher emissivity./NASA/JPL/ESA.
Posted: 08 Apr 2010 10:24 AM PDT
It's been a little while since the Hubble Space telescope bestowed a mind-blowing space photo on us, but this one was worth the wait.
This swirly, spooky, sparkly shot is of Messier 66, the largest of three spiral galaxies that make up the Leo triplet, 35 million light-years away. The galaxy measures around 100,000 light-years across and has odd, asymmetrical arms that were most likely pulled out of place by the gravity of the other two galaxies in the triplet.
The brown stripes are made up of dust, and the blue and pink bright areas in the galaxies are star clusters. Messier 66 is popular with astronomers because it has had an impressive three supernova explosions since 1989.
Images: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration.
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