Bilingual children develop problem-solving skills before children who speak only one language, says a Canadian researcher who has spent almost 20 years studying how language affects learning in young children.

Learning two languages at an early age gives children an edge when it comes to processing information, says Ellen Bialystok, a psychology professor at Toronto's York University who studied language development and early literacy in hundreds of children.

"I'm finding over 20 years of research that learning two languages does change some early aspects of cognition."

The children she studied spoke French, Spanish, Chinese or Hebrew as well as English, and came from middle-income backgrounds. The children in the control group were also from middle-income families, but they spoke only English.

Bialystok found that bilingual children can figure out problems that contain misleading information at a younger age. For example, children in both groups were told that moon means sun and sun means moon. Then they were asked to think of the sky at night when the "sun" is up. What's the sky like? The correct answer is "dark."

In another problem, children were shown two "apartment buildings" made of blocks. One tower, the shorter one, was made of many small blocks. The second tower, the taller one, was made of fewer large blocks. The bilingual children were more likely to conclude that there were more apartments in the shorter tower.

Bilingual children show the ability to ignore misleading information a year before unilingual children, a skill that boosts all kinds of problem-solving, Bialystok said.

"It turns out to be important," she said. "Bilingual kids are at least a year ahead. That's a big advantage."

Bialystok believes that bilingual children are able to "edit" their attention because they have to block out one language when working in the other.

"Where you pay attention is one of the really important aspects of development," she said. "Languages are always active. In order for them not to intrude, you have to turn them off. It spills into everything you're thinking of."

It doesn't appear to matter what two languages the children speak, Bialystok said. But she added that she doesn't know how long bilingual children maintain their edge: "I have no evidence that they read earlier."

Bialystok doesn't know if bilingual children maintain their early leads, but she wants to find out. The kinds of test researchers use on preschoolers and children in the primary grades aren't effective with older children, she said. "If these differences are real, we'll see that bilingual adults process information much differently," she said.

Bialystok noted that there has been a long-running politically charged controversy over bilingualism's effects on children and learning. She pointed out that her studies were with children who spoke two languages at home, and not with children who learned a second language through an immersion program at school. But she added that being exposed to only one language as a child isn't harmful.