Science Digest

Monday, June 22, 2009

Positive Is Negative

Despite what all those self-help books say, repeating positive statements apparently does not help people with low self-esteem feel better about themselves. In fact, it tends to make them feel worse, according to new research.

Joanne Wood of the University of Waterloo in Ontario and two colleagues conducted experiments in which they asked students to repeat statements to themselves such as "I am a lovable person" -- then measured how it affected their mood.

"From at least as far back as Norman Vincent Peale's "The Power of Positive Thinking" (1952), the media have advocated saying favorable things to oneself," the researchers wrote in a recent issue of the journal Psychological Science. "At this moment, thousands of people across North America are probably silently repeating positive statements to themselves."

But in one of their studies involving 32 male and 36 female psychology students, the researchers found that repeating the phrase did not improve the mood of those who had low self-esteem, as measured by a standard test. They actually ended up feeling worse, and the gap between those with high and low self-esteem widened.

The findings did not change even if participants were instructed to focus on how the statement might be true about them, as they were in a second study involving 12 men and 39 women.

The results "suggest that for certain people, positive self-statements may not only be ineffective, but actually detrimental," the researchers wrote. More research is needed to understand that effect. "One possibility is that, like over-positive praise, they can elicit contradictory thoughts" and prompt people to focus on how the positive statement is not true about them.

-- Rob Stein

Missing Digits

Scientists have long believed that birds inherited their three-fingered claws from dinosaurs. The transition from five fingers to three took place while dinosaurs still roamed the earth, but a long-running controversy has centered on which two fingers were lost through natural selection. The conventional wisdom has long been that the most advanced species of therapods, the dinosaurs who are the ancestors of today's birds, lost the last two fingers on their hands -- or, to anthropomorphize, the "ring finger" and the "little finger."

A new dinosaur find in China suggests a different answer: The first and fifth fingers were lost. Scientists said that a dinosaur found in a 159-million-year-old deposit in a mine in northwestern China was a transitional beast between five-fingered and three-fingered creatures, and that the fossil revealed an animal whose first finger had shrunk sharply and whose second finger had greatly increased in size.

James Clark at the George Washington University and his colleagues said each subsequent finger on the dinosaur took on the shape of the digit next to it, eliminating the last finger as well.

The recently discovered dinosaur paid a nasty price for its contribution to science: It has been dubbed Limusaurus inextricabilis -- as in "mire lizard that could not escape" -- because it was found in a pit where several dinosaurs apparently died stacked above one another.

-- Shankar Vedantam


America is going back to the moon. This has been the official NASA aspiration for the past five years, but now it is really happening, thanks to two robotic spacecraft launched together Thursday on a single Atlas V rocket at the Kennedy Space Center.

The Lunar Reconnaissance Orbiter (LRO) is expected to reach the moon Tuesday morning and then spend the next year mapping the lunar surface from about 30 miles up. Although the moon has been photographed and mapped since the Soviet Union sent the first flyby mission in 1959, the $500 million LRO will produce observations of the entire moon and will help identify geologically interesting locations for future human missions. The orbiter will also send back images of the remnants of Apollo spacecraft, including the moon rovers, idled for the past four decades.

"We actually have better maps of Mars than we do of the moon. That's what we're trying to fix," said NASA's Ashley Edwards.

The second probe, called the Lunar Crater Observation and Sensing Satellite (LCROSS), will have its main event in October, when it sends a spent rocket stage smashing into a crater at the lunar pole. That impact will throw up dust and debris that will be studied by the satellite, which will then crash into the crater to create another plume. The impacts will be scrutinized by the Hubble Space Tele scope and should be visible to amateur astronomers with relatively modest telescopes.

The greater significance of the paired missions is that, after years of talk about returning to the moon, NASA has hardware flying. The agency hopes to land astronauts on the moon by 2020.

"This is really NASA's first mission in our efforts to go back to the moon," said Dewayne Washington of NASA's Goddard Space Flight Center, which developed the LRO.

-- Joel Achenbach

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