Toddlers who already speak two languages are better than their peers at a particular kind of problem solving that requires knowing when it's okay to change the rules, according to a new study.

"Most of the research on the benefits of bilingualism comes from children aged four years and up," said senior author Diane Poulin-Dubois of Concordia University in Montreal. "So showing a more precocious benefit is important."

"What is more important is that we observed that within the bilingual group those who became more bilingual over seven months (learning more doublets or cross-language synonyms) benefited even more," she told Reuters Health by email.

Previous research has linked speaking two languages to thinking benefits later in life, including increased odds of regaining normal cognitive function after a stroke (see Reuters story of Nov. 25, 2015 here:

The new study compared 39 bilingual children in Montreal who were exposed to English and French from birth, with 43 monolingual children in San Diego, California. Language exposure was determined by interviewing parents.

Researchers assessed each child's expressive vocabulary at 24 and 31 months of age, and also administered tasks designed to test memory, conflict resolution and other brain functions at the second assessment.

As expected, monolingual children expressed more words in their vocabularies than bilinguals.

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In the conflict task, the children played with several big blocks and several little blocks and were repeatedly told that the big blocks belonged in a big bucket and the little blocks in a little bucket. Then the experimenter told the child to play a silly game and put the little blocks in the big bucket, and vice versa.

If the child complied, that indicated he or she was able to inhibit the rule they learned first and adhere to the new rule.

The children performed about the same on the first round of block-in-bucket tests, matching the little blocks with the little bucket. But after the rule changed, bilingual children were more often able to put the little blocks in the big bucket, according to the results in the Journal of Experimental Child Psychology.

Based on vocabulary increases in the seven months between assessments, bilingual children whose ability to switch between languages improved the most scored higher on the thinking and conflict tasks than bilingual children who did not become more fluent over time.

When you know two languages, you cannot use both of them simultaneously, Poulin-Dubois said.

"It is known that both languages are active all the time so that requires keeping one out of the way as you speak the other," she said. "This practice in selective attention and inhibitory control is a mental exercise that is reflected outside language in a context where you have to avoid being distracted by other stimuli or well known rules."

In adult life, conflict inhibition allows us to keep our focus on goals, like keeping a diet or following an exercise program, and not be distracted, she said.

General IQ could have had some influence on the results, although it was not tested, said Chantel S. Prat of the Institute for Learning and Brain Sciences at the University of Washington in Seattle, who was not part of the new study.

"In any case, I do think bilingual brains have a harder job, and that there are broader consequences/benefits of bilingual language control for mind and brain," Prat told Reuters Health by email.

"Studies have reported differences between simultaneous bilinguals (learning two languages from birth) and sequential bilinguals (learning one language before learning another) in both cognitive performance and neural correlates between these two groups of bilinguals," said Natalie Hiromi Brito of Columbia University Medical Center in New York, who also was not part of the new study.

"Additionally, a more recent study found that early exposure (before the age of 3) to a language continues to influence neural processing, even after the language is no longer used," Brito told Reuters Health by email.

Learning a second language, even later in life, has social and cognitive benefits, Poulin-Dubois said. "And to maintain and increase the benefits, keep using the two languages."

But, "the results of a single study should not influence an individual's decision to learn a second language or to raise their children multilingual," Brito said. "Encouraging multilingualism and bilingual education would be wonderful regardless of the reported cognitive differences."