As another example of a test, children sit in front of a computer screen on which either a red square suddenly flashes on the left of the screen or else a blue square flashes on the right of the screen. The keyboard below the screen includes a red key and also a blue key, and the child must push the key with the same color as the flashing square. If the red key is on the left of the keyboard and the blue key is on the right—i.e., in the same relative position as the flashing square of the same color on the screen—then bilinguals and monolinguals perform equally well. But if the positions of the red and blue keys are reversed to create confusion—i.e., if the red key is on the left side of the keyboard but the blue flashing square is the one on the left side of the screen—then bilinguals perform better than monolinguals.
It was initially expected that this advantage of bilinguals at tests involving rule changes or confusing information would apply only to tasks involving verbal cues. However, the advantage proves to be broader, and to apply also to non-verbal cues of space, color, and quantity (as in the two examples that I just described). But this hardly means that bilinguals are better than monolinguals at everything: the two groups tend to perform equally well at tasks without rule changes to be attended to, and without misleading cues to be ignored. Nevertheless, life is full of misleading information and changing rules. If bilinguals’ advantage over monolinguals in these trivial games also applies to the abundance of confusing or shifting real-life situations, that would mean a significant advantage for bilinguals.
One interesting recent extension of these comparative tests is to infants. One might imagine that it would be meaningless or impossible to test “bilingual infants”: infants can’t speak at all, they can’t be described as bilingual or monolingual, and they can’t be asked to perform tests by sorting cards and pushing keys. In fact, infants develop the ability to discriminate speech that they hear long before they can speak themselves. One can test their powers of discrimination by watching whether they can learn to orient differently to two different sounds. It turns out that newborn infants, who have had no exposure to any of the world’s languages, can discriminate between many consonant and vowel distinctions used in one or another of the world’s languages, whether or not it happens to be their “native” language (which they haven’t heard except from inside the womb). Over the course of their first year of life, as they hear speech around them, they lose that initial ability of theirs to discriminate non-native distinctions that they aren’t hearing around them, and they sharpen their ability to discriminate native distinctions. For instance, the English language discriminates between the two liquid consonants l and r, while the Japanese language doesn’t; that’s why native Japanese people speaking English sound to native English-speakers as if they are mispronouncing “lots of luck” as “rots of ruck.” Conversely, the Japanese language discriminates between short and long vowels, while the English language doesn’t. However, newborn Japanese infants can discriminate between l and r, and newborn English infants can discriminate between short and long vowels, but each loses that ability over the first year of life because the distinction carries no meaning.
Recent studies have concerned so-called crib bilinguals: i.e., infants whose mother and father differ from each other in native language, but whose mother and father have both decided to speak her or his own language to the infant already from day 1, so that the infant grows up hearing two languages rather than just one language. Do crib bilinguals already gain over monolinguals the advantage in executive function, enabling them to deal better with rule switches and confusing information, that is apparent after the child can actually speak? And how does one test executive function in a pre-verbal infant?
A recent ingenious study by the scientists Ágnes Kovács and Jacques Mehler, carried out in the Italian city of Trieste, compared seven-month “monolingual” infants with infants “bilingual” in Italian plus either Slovenian, Spanish, English, Arabic, Danish, French, or Russian (i.e., hearing one language from their mother and the other language from their father). The infants were trained, conditioned, and rewarded for correct behavior by being shown a cute picture of a puppet popping up on the left side of a computer screen; the infants learned to look in the direction of the puppet and evidently enjoyed it. The test consisted of pronouncing to the infant a nonsense trisyllable with the structure AAB, ABA, or ABB (e.g., lo-lo-vu, lo-vu-lo, lo-vu-vu). For only one of the three structures (e.g., lo-lo-vu) did the puppet appear on the screen. Within 6 trials, on hearing lo-lo-vu both “monolingual” and “bilingual” infants learned to look towards the left side of the screen to anticipate the appearance of the cute puppet. Then the experimenter changed the rules and made the puppet appear on the right side (not on the left side) of the screen, in response not to the nonsense word lo-lo-vu but to lo-vu-lo. Within 6 trials, the “bilingual” infants had unlearned their previous lesson and had learned the new correct response, but the “monolingual” infants even after 10 trials were still looking at the now-wrong side of the screen on hearing the now-wrong nonsense word.
Alzheimer’s disease
One can extrapolate from these results, and speculate that bilingual people may have an advantage over monolingual people in negotiating our confusing world of changing rules, and not merely in the trivial tasks of discriminating lo-lo-vu from lo-vu-lo. However, you readers will probably require evidence of more tangible benefits before you make the commitment to babble consistently in two different languages to your infant children and grandchildren. Hence you will be much more interested to learn about reported advantages of bilingualism at the opposite end of the lifespan: old age, when the devastating tragedy of Alzheimer’s disease and other senile dementias lies in store for so many of us.
Alzheimer’s disease is the commonest form of dementia of old age, affecting about 5% of people over the age of 75, and 17% of those over the age of 85. It begins with forgetfulness and a decline of short-term memory, and it proceeds irreversibly and incurably to death within about 5 to 10 years. The disease is associated with brain lesions, detectable by autopsy or (in life) by brain-imaging methods, including brain shrinkage and accumulation of specific proteins. All drug and vaccine treatments to date have failed. People with mentally and physically stimulating lives—more education, more complex jobs, stimulating social and leisure activities, and more physical exercise—suffer lower rates of dementia. However, the long latency period of up to 20 years between the beginning of protein build-up and the later appearance of Alzheimer’s symptoms raises questions of cause and effect about the interpretation of these findings concerning stimulating lives: does stimulation itself really decrease Alzheimer’s symptoms, or were those individuals instead able to lead stimulating lives precisely because they were not suffering from early stages of protein build-up, or because of genetic advantages that also protected them against Alzheimer’s disease? In the hope that stimulating lives might be a cause rather than a result of reduced disease processes, older people afraid of developing Alzheimer’s disease are sometimes urged to play bridge, play challenging online games, or solve Sudoku puzzles.