'Mum and dad made me multi-task better'
Bilingual children are less easily confused and are less likely to develop Alzheimer's when they grow up.
These are just some of the claims to emerge from recent studies on bilingualism which the American scientist and author Jared Diamond has reviewed for an article in the journal Science.
Globally, people who speak two or more languages are believed to outnumber those who speak only one language. But up until the 1960s, research appeared to show that bilingual children acquired language more slowly.
According to Professor Diamond, who is now learning his 12th language, such assumptions are now outdated, with more recent work suggesting no great differences in the cognitive and linguistic progress of multilingual vs monolingual children.
But there are areas, he says, where more languages might be better.
He points to work by Ágnes Kovács and Jacques Mehler. They tested the responses of infants who were being brought up by parents who each spoke different languages to their children, with infants who were only exposed to one parental language.
What they found was the "bilingual" children adjusted more quickly to changes, and were more quickly anticipating on which side of the screen the puppet would appear based on the speech clue.
They devised a game with a puppet appearing on different sides of a screen, but with the puppet's appearance preceded by a different nonsense word.
In an interview with the BBC World Service radio progamme Science in Action, Professor Diamond said the study suggested that individuals reared bilingually were better able to focus in confusing situations.
"A baby that has been reared bilingually has learned from the age of three months to pay attention to the sounds of Italian and to ignore mummy who speaks Chinese," he says by way of example. "But if mummy starts speaking, the baby will start paying attention to Chinese sounds and ignore Italian."
"An infant reared bilingually has to practice at paying attention which the rest of us don't."
In another Canadian study he examines, it was suggested that those who speak more than one language were less likely to develop forms of dementia, including Alzheimer's. A survey of hundreds of elderly Canadian dementia patients, found the bilingual patients on average developed symptoms at least four years later than their monolingual peers.
The possible explanation was that bilingual individuals were exercising their brains in ways which their monolingual peers were not, and thereby delaying dementia.
"It would be really powerful if it turned out, as appears to be the case, you get five years of protection from Alzheimer's by learning another language," says Professor Diamond.
"But suppose you're a Swedish shopkeeper who speaks five languages. You may get 25 years of protection against Alzheimer's, which means you won't get it until you're 102 years old, so you're not going to get it at all."
Professor Diamond concedes that a few studies do not make a conclusive case for the advantages of multilingualism.
But he is urging people not to repeat the mistakes of many immigrants to the United States, including some in his own family, who chose not to pass on their native languages to their children once they arrived on US shores.
"At minimum don't be prejudiced at learning another language.
"If your parents are immigrants insist that they teach you their language and if your parents are not immigrants then go to some effort yourself to learn another language.
"At minimum it's fun and at maximum it may push off the onset of Alzheimer's symptoms by five, 10, 15 or 20 years."