A June 14 Science Notebook item incorrectly said there is only one free-roaming buffalo herd in the nation, in Yellowstone National Park. Smaller free-roaming herds exist in the Henry Mountains of Utah and Grand Teton National Park in Wyoming. (Published 6/16/04)

Bilingualism's Brain Benefits

Bilingual speakers are better able to deal with distractions than those who speak only a single language, and that may help offset age-related declines in mental performance, researchers say.

In studies conducted in Canada, India and Hong Kong, psychologists determined that individuals who spoke two languages with equal proficiency and used both equally did better than monolingual volunteers on tests that measured how quickly they could perform while distracted.

"The bilingual advantage was greater for older participants," the researchers wrote yesterday in the journal Psychology and Aging, adding that "bilingualism appears to offset age-related losses" in certain mental processes.

Researchers used the Simon task, a test used to measure mental abilities that are known to decline with age. Test takers saw a red or a blue square flash on a computer screen and were told to depress one or the other of the two "shift" keys depending on which color appeared. As previous research has found, performance slowed when the colored squares moved from their original positions.

Three experiments showed that bilingual speakers of Cantonese and English, Tamil and English or French and English consistently outperformed English-only speakers, said the researchers at York University and the Rotman Research Institute in Toronto, and Dalhousie University in Halifax, Nova Scotia.

The team, led by Ellen Bialystok at York University, hypothesized that the ability to hold two languages in the mind at the same time, without allowing words and grammar from one to slip into the other, might account for the greater control needed to perform well on the Simon task. An alternate hypothesis is that bilinguals have superior working memories for storing and processing information.

-- Shankar Vedantam

Feelings Toward Grandparents

Genes may influence how close a grandchild feels toward a grandparent, according to new research.

William von Hippel of the University of New South Wales in Australia and colleagues hypothesized that grandparents tended to invest more time and emotional energy in grandchildren who were most likely to be their genetic offspring. The possibility of infidelity, for example, means that a grandparent would be more confident that a daughter's children were truly genetic kin than a son's.

"A maternal grandmother knows with certainty that her genetic material is passed to her grandchildren through her daughter, but a paternal grandfather has a double uncertainty -- he has no certainty that either his son or his grandchildren bear his genetic material," von Hippel said.

To test the theory, von Hippel and his colleagues asked 787 university students to rate their emotional closeness to each biological grandparent. In a paper being published in the journal Personality and Social Psychology Bulletin, the researchers report that, indeed, the participants tended to feel closest to their mothers' mothers, followed by their mothers' fathers, then their fathers' mothers, and finally their fathers' fathers.

This was only true, however, when the paternal grandmother had other grandchildren through a daughter, making those grandchildren genetically more certain. When paternal grandmothers had grandchildren only through a son, the degree of closeness was equal to that of maternal grandfathers, researchers found.

"Grandparents must spread their time and resources across grandchildren, and genetic certainty clearly influences this," von Hippel said.

-- Rob Stein

Bison Domestication Soars

The number of bison raised commercially has soared in recent years and totaled 231,950 animals in 2002, the Department of Agriculture said last week in announcing its first-ever census.

They dwarf the number of wild buffalo, which is between 15,000 and 16,000. Before the Europeans settled the West, buffalo numbered between 20 million and 30 million. The only remaining free-roaming herd, which is 3,800 strong, lives in Yellowstone National Park, said Josh Osher, coordinator for the Buffalo Field Campaign. Their numbers are controlled because of the limited habitat available.

According to the USDA, bison are being produced in 4,132 operations across the country. South Dakota is the leading buffalo-producing state, with 40,168 bison.

The last accurate tally of domesticated bison was conducted by the University of Wyoming in 1997, which counted 138,000.

Dave Carter, executive director of the National Bison Association, said that "ranchers try to keep them as genetically pure as possible," though some have been bred with cattle.

Osher said he "hates to see a lot of domestication of a wild animal," but added that he preferred to see buffalo being raised, rather than cows, because "they're better for the landscape, in terms of grazing."

-- Juliet Eilperin

Bison are being produced in 4,132 operations across the country, the USDA reports.