The World Until Yesterday

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 Agnes Kovacs 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.

Intriguing results of the last few years suggest a protective effect of life-long bilingualism against Alzheimer’s symptoms. Among 400 patients studied at clinics in Toronto, Canada, mostly in their 70s, and with a probable diagnosis of Alzheimer’s disease (or other dementias in a few cases), bilingual patients showed their first symptoms at an age 4 or 5 years older than did monolingual patients. Life expectancy in Canada is 79, hence a delay of 4–5 years for people in their 70s translates into a 47% decrease of probability that they will develop Alzheimer’s symptoms at all before they die. The bilingual and monolingual patients were matched in occupational status, but the bilingual patients had received on the average lower (not higher) levels of education. Because education is associated with lower incidence of Alzheimer’s symptoms, this means that differences in education could not explain the lower incidence of symptoms in the bilingual patients: their lower incidence was despite their having received less education. A further intriguing finding was that, for a given level of cognitive impairment, bilingual patients had more brain atrophy revealed by brain-imaging methods than did monolingual patients. Expressing this differently, bilingual patients suffer less cognitive impairment than do monolingual patients with the same degree of brain atrophy: bilingualism offers partial protection against the consequences of brain atrophy.

The protection afforded by bilingualism does not raise the same uncertainties of interpretation about cause versus effect raised by the apparent protection offered by education and stimulating social activities. The latter might be results rather than causes of early stages of Alzheimer’s lesions; and genetic factors predisposing one to seek education and social activities might also protect one against Alzheimer’s disease. But whether one becomes bilingual is determined in early childhood, decades before the earliest Alzheimer’s brain lesions develop, and regardless of one’s genes. Most bilingual people become bilingual not through any decision or genes of their own, but through the accident of growing up in a bilingual society, or of their parents emigrating from their native land to a land with a different language. Hence the reduced Alzheimer’s symptoms of bilinguals suggest that bilingualism itself protects against Alzheimer’s symptoms.

How might this be? A short answer is the aphorism “Use it or lose it.” Exercising most body systems improves their function; failing to exercise them lets their function deteriorate. This is the reason why athletes and artists practise. It’s also the reason why Alzheimer’s patients are encouraged to play bridge or online games, or to solve Sudoku puzzles. But bilingualism is the most constant practice possible for the brain. Whereas even a bridge or Sudoku fanatic can play bridge or solve Sudoku puzzles for only a fraction of a day, bilingual people impose extra exercise on their brain every second of their waking hours. Consciously or unconsciously, their brain is constantly having to decide, “Shall I speak, think, or interpret sounds spoken to me according to the arbitrary rules of language A, or of language B?”

Readers will share my personal interest in some unanswered but obvious further questions. If one extra