Which is probably as suspect as all other research. But at least it lets me feel good about myself:
Prof. Bialystok first noticed bilingual children were proficient in blocking out irrelevant information about 20 years ago. When asked to identify a grammatically correct sentence, for example, both bilinguals and monolinguals are, by age 5, able to choose, "Apples grow on trees," over "Apple trees on grow" as the correct one.
But when it came to asking "Apples grow on noses" versus "Apples nose on grow," only the bilingual children were able to choose the right answer. Although the first sentence is grammatically correct, monolingual children could not get over its silliness. "That's crazy," they'd shout, "You can't say that!"
"We have been able to show on a huge range of cognitive tests that bilinguals are always better at problems with tricky, misleading information," Prof. Bialystok said.
On average, she said, monolingual children take a year longer to learn to block out irrelevant information and focus on a specific task.
It's almost worth it to be bilingual, then, even if it means that I write English like the hound of Budapest of My Fair Lady.
Via Kos who is also blessed with bilingualism...