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A new psychological study suggests that human personality continues to change after 30 -- in fact, well into middle age and beyond -- a finding that is in sharp contrast to many saws and stereotypes about growing old.

"People have different ideas of what getting older means," said Sanjay Srivastava, a Stanford University psychologist. "Some people think you get set in your ways, some people think it means decline." But "the changes we found were, on average, for the better. Getting older from 21 to 60 is a process of getting better at things."

A team of psychologists polled about 130,000 people in the United States and Canada over the Internet and gave them tests to measure broad personality traits such as being conscientious, agreeable and extroverted. Not surprisingly, they reported in the Journal of Personality and Social Psychology, both men and women grew more conscientious after they turned 30.

But they also found that people became more agreeable -- the biggest changes in this trait occurred in people's thirties and forties. They defined "agreeable" as acting in supportive and nurturing ways, rather than being cold and hostile.

And contrary to Hollywood stereotype, older people remained open to new experiences. "There is the popular notion that older people are closed off and not interested in the world around them," said Srivastava. "The declines were very small."

-- Washington Post

Few 'Back to Sleep' problems for infants

It has been 11 years since the American Academy of Pediatrics began recommending that parents place infants on their backs or sides at bedtime to reduce the incidence of sudden infant death syndrome (SIDS). By 1998, the percentage of parents complying with that advice rose from 30 percent to 83 percent, and the incidence of SIDS declined 40 percent.

Yet many parents have wondered whether the "Back to Sleep" campaign might have problems of its own, including higher rates of spitting up (with the risk of choking on vomit), more ear infections, or a greater frequency of colic or respiratory problems.

A new study should reassure those parents. Researchers used surveys to track the sleep positions and more than a dozen health measures for 3,733 infants, from 1 month to 6 months of age. They tracked such symptoms as fever, cough, trouble sleeping, stuffy nose, vomiting and diarrhea, and also tallied visits to doctors' offices.

Compared with infants placed face down, those on their backs or sides were not at increased risk for any of the symptoms, nor did they have more visits to the doctor, the team reported in Archives of Pediatrics and Adolescent Medicine. Indeed, infants on their backs or sides had fewer fevers at 1 month and fewer instances of trouble sleeping and stuffy noses at 6 months. They also had lower rates of doctors' visits for ear infections at 3 months and 6 months.

-- Washington Post

Meteorites traced to asteroid collision

Geologists have traced a bonanza of Swedish meteorites back to a huge asteroid collision that took place in space about 480 million years ago.

Fifty fossilized meteorites, most of the world's total of such meteorites, lie entombed in limestone taken from quarries in southern Sweden. Birger Schmitz and his colleagues from Goteborg University in Sweden found the rocks all trace back to an explosive event in the asteroid belt, which rained a shower of meteorites onto Earth's surface, they reported in Science.

The massive explosion has repercussions even today: Up to one-quarter of all incoming meteorites are from the same event.

-- Dallas Morning News

Ants have role in rain forest decline

Marauding ants may be helping destroy tropical rain forests, biologists have found.

A new study in Science confirms that some rain forest ants are herbivores, not carnivores as previously thought. The ants prey indirectly on trees rather than directly on other insects.

The research, conducted in Peru and Borneo, shows that the ants eat mostly honeydew, a sweet liquid made from the sap of rain forest trees. Other insects, such as aphids and treehoppers, eat the sap and excrete it as honeydew; the ants then eat the honeydew.

With so many ants in the rain forest, other insects are forced to suck trees dry to feed them, writes a team of scientists led by Diane Davidson of the University of Utah.

-- Dallas Morning News