Chimps Show Desire to Fit In

Humans are apparently not the only creatures who like to fit in. New research indicates that chimps have an innate desire to conform to the norms of their group.

Researchers from the University of St. Andrews in Scotland and Emory University in Atlanta taught dominant females named Georgia and Erika at Emory's Yerkes National Primate Research Center two different techniques for freeing a piece of food from a special apparatus.

When the chimps were reunited with their respective groups, they immediately became the center of attention as they started using their newly acquired skills. Each one's unique approach spread quickly through her clan.

A third group of chimps that did not have an "expert" was unable to figure out how to get food from the device, the researchers reported in a paper published online yesterday in the journal Nature.

When the researchers tested the chimps again two months later, each group was still using its unique solution to the stuck-food problem.

Moreover, when some chimps independently figured out the method that the other group had been taught, they quickly abandoned it and reverted to the norms of their group.

"The evidence that the chimpanzees knew the alternative methods but reverted to the conventions of their group shows a level of conformity that has only previously been seen in our own species," said Andrew Whiten of St. Andrews.

-- Rob Stein

Fewer Boys Near Industrial Site

Chippewa Indians living in Ontario near several petrochemical, polymer and chemical industrial plants have seen the number of male births in their community fall sharply since 1994, according to a study published online Wednesday in the journal Environmental Health Perspectives.

The ratio between male and female babies is considered a key indicator of a population's reproductive health.

Worldwide, males account for between 50.4 and 51.9 percent of all births, and in Canada they represent 51.2 percent of births. But Canadian researchers found that among the 800 Chippewas living in the Aamjiwnaang First Nation community near Sarnia, Ontario, the proportion of male births has been dropping for the past decade. Males accounted for only 41.2 percent of births between 1994 and 2003, and 34.8 percent of births between 1999 and 2003.

One of the study's authors, Constanze A. MacKenzie, a fourth-year medical student at the University of Ottawa, said she and other researchers have launched a follow-up study to determine the connection between the decline in male births and the area's high rate of chemical exposure. Other studies have found similar sex ratio changes in area fish, bird and turtle populations near the St. Clair River.

"Although there are several potential factors that could be contributing to the observed decrease in sex ratio of the Aamjiwnaang First Nation, the close proximity of this group to a large aggregation of industries and potential exposures to compounds that may influence sex ratios warrants further assessment into the types of chemical exposures for this population," the authors wrote.

-- Juliet Eilperin

Games Linked to Aggression

A new analysis of research done over the past 20 years into the effects of violent video games has concluded that the popular entertainment provokes aggressive behavior in many young players and leads to increases in hostility in others.

The review, presented last week at the American Psychological Association's annual convention in Washington, analyzed a range of studies that found that violent video games led, at least temporarily, to more aggressive fantasies and acting out and were especially arousing to girls who were less familiar with the games.

The authors initiated their review in part because of a 2001 federal court decision that overturned an Indianapolis law prohibiting video parlors from allowing children to use graphically violent video games unless accompanied by a parent. In his decision, U.S. Appeals Court Judge Richard Posner said that video game studies had not found clear evidence that violent video games increased the average level of violence among players.

The authors of the new study, Jessica Nicoll and Kevin Kieffer of Saint Leo University in Florida, disagreed. "Although no one study has conclusively demonstrated a cause-and-effect relationship between exposure and behavior, based on the results presented here it is difficult to argue that there is no relationship between violent game play and subsequent aggressive behavior," they wrote.

Among the more provocative studies was one of 600 eighth- and ninth-graders, which found that the children who spent the most time playing violent video games were rated by their teachers as the most hostile and were more likely to get into fights with other students. In addition, the authors found, students who played the violent games were prone to imitating the moves they just acted out in their games.

-- Marc Kaufman

A skill learned by one chimpanzee is quickly adopted by all of the clan, a new study shows.