The Benefits of Multilingualism Jared Diamond Science 330, 332 (2010); DOI: 10.1126/science.1195067

This copy is for your personal, non-commercial use only.

If you wish to distribute this article to others, you can order high-quality copies for your colleagues, clients, or customers by clicking here.

The following resources related to this article are available online at www.sciencemag.org (this infomation is current as of November 26, 2010 ): Updated information and services, including high-resolution figures, can be found in the online version of this article at: http://www.sciencemag.org/content/330/6002/332.full.html This article cites 8 articles, 2 of which can be accessed free: http://www.sciencemag.org/content/330/6002/332.full.html#ref-list-1 This article appears in the following subject collections: Psychology http://www.sciencemag.org/cgi/collection/psychology

Science (print ISSN 0036-8075; online ISSN 1095-9203) is published weekly, except the last week in December, by the American Association for the Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. Copyright 2010 by the American Association for the Advancement of Science; all rights reserved. The title Science is a registered trademark of AAAS.

Downloaded from www.sciencemag.org on November 26, 2010

Permission to republish or repurpose articles or portions of articles can be obtained by following the guidelines here.

PERSPECTIVES SOCIAL SCIENCE

The Benefits of Multilingualism

Bilingual rearing of children, instead of confusing them, may bring lifelong advantages.

Jared Diamond

332

15 OCTOBER 2010 VOL 330 SCIENCE www.sciencemag.org Published by AAAS

CREDIT: JOE SUTLIFF/WWW.CDAD.COM/JOE

Downloaded from www.sciencemag.org on November 26, 2010

M

ultilingualism—the abilresult, multilinguals have constant ity to understand and unconscious practice in using the speak several languages— executive function system. is exceptional in the United States Recent studies assess this abilbut common elsewhere, especially in ity by assigning to subjects gamesmall-scale traditional societies. For like tasks designed to be confusing, instance, once while I was camped either because the task rules change with some New Guinea Highlanders unpredictably, or because the task conversing simultaneously in sevpresents misleading cues that must eral local languages, I asked each be ignored (1–3, 7, 8). For instance, man to name each language in which children are shown cards depicthe could converse. It turned out that ing either a rabbit or a boat, colored everyone present spoke at least 5 laneither red or blue, with or without a guages, and the champion was a man star. If the card has a star, the chilwho spoke 15. What are the cognidren must sort cards by color; if a tive effects of such multilingualstar is absent, they must instead sort ism? Recent studies (1–5) show that cards by the object depicted. It turns children raised bilingually develop out that monolingual and bilingual a specific type of cognitive benefit subjects are equally successful if during infancy, and that bilingualthe rule remains the same from trial ism offers some protection against to trial (e.g., “sort by color”), but symptoms of Alzheimer’s dementia Competing inputs. A typical moment in the life of a typical Science monolinguals have more difficulty reader, who is simultaneously processing various sensory inputs with his in old people. than bilinguals at accommodating to eyes, ears, nose (the smell of the food), skin touch receptors (the friend’s Bilingual education is politi- handshake, the briefcase being held), and proprioreceptors (the cramp a switch in rules. Although success cally controversial in the United in his leg), and having competing thoughts. Depending on the circum- at these games won’t by itself make States. Even immigrants whose stances, any one of those stimuli or thoughts may warrant full attention. one rich or happy, our lives are full native language is not English often Recent studies suggest that multilingual people may have an advantage of other misleading information and believe that their children should over monolinguals in sifting and managing these distracting stimuli. rule changes. If bilinguals’ advanlearn only English and will be contage over monolinguals in these fused by learning two languages simultane- the figure). To succeed in doing anything at games also applies to real-life situations, that ously. Until the 1960s, research appeared to all, we must temporarily inhibit 99% of those could be useful for bilinguals. show that bilingual children acquired lan- inputs and attend to just 1% of them, and the While this superior executive function guage more slowly than monolingual chil- appropriate choice varies with the circum- has been reported for bilinguals of all ages, dren and achieved smaller vocabularies. But stances. That selective attention involves a set results for the youngest and the oldest subother variables correlated with bilingualism of processes, termed executive function, that jects are of particular interest. Kovács and in those early studies, such as schooling and reside in the prefrontal cortex and develop Mehler (4, 5) tested confusing game tasks on parental socioeconomic status, confounded especially over the first 5 years of life (9). “monolingual” infants and “crib bilingual” their interpretation. More recent studies, Multilingual people have a special chal- infants—i.e., infants reared from birth to comparing subjects matched for those other lenge involving executive function. Mono- hear and eventually to speak two languages, variables, have found bilinguals and mono- linguals hearing a word need only compare it because mother and father speak to the infant linguals to be largely similar in cognition and with their single stock of arbitrary phoneme in different languages. It might seem meanlanguage processing (6–8). (sound) and meaning rules, and when utter- ingless to describe infants who cannot speak The clearest difference identified by these ing a word they draw it from that single stock. as monolingual or bilingual. Actually, infants studies involves an advantage that bilinguals But multilinguals must keep several stocks learn to discriminate the sounds of the lanhave over monolinguals, rather than a disad- separate. For instance, on hearing the pho- guage or languages heard around them and vantage. Our minds are assaulted by varied nemes b-u-rr-o, a Spanish/Italian bilingual to ignore sound distinctions not heard around sights, sounds, and other external sensory instantly interprets them to mean either “don- them. For instance, Japanese infants lose, and inputs, plus thoughts and proprioreceptive key,” if the context is Spanish, or “butter,” if English infants retain, the ability to discrimisensations (which make us aware of the rel- the context is Italian. Multilinguals partici- nate the liquid consonants l and r, which the ative positions of our own body parts) (see pating in a multilingual conversation, like Japanese language does not distinguish. my New Guinea Highland friends or shop How can one test responses to speech by assistants in Scandinavian department stores, those preverbal infants? Kovács and Mehler Geography Department, University of California Los Angeswitch frequently and unpredictably between (4, 5) devised a clever protocol in which infants les, Los Angeles, CA 90095–1524, USA. E-mail: jdiamond@ geog.ucla.edu their stocks of phoneme/meaning rules. As a looked for pictures of a puppet appearing on

PERSPECTIVES showed their first symptoms at an age 5 years older than did monolingual patients matched in other respects. Canadian life expectancy is 79, hence a 5-year delay for people in their 70’s translates into a 47% decreased probability that they will develop Alzheimer’s symptoms at all before they die. How might this be? A short answer is the aphorism, “Use it or lose it.” Exercising body systems improves their function; not exercising them lets their function deteriorate. That’s why athletes and musicians practice. It’s also why Alzheimer’s patients are encouraged to play brain-challenging games like bridge or to solve Sudoku puzzles. But bilingualism is arguably the most constant practice possible for the brain. Whereas even a Sudoku fanatic can spend only a fraction of a day on Sudoku puzzles, bilinguals impose extra exercise on their brain every minute of their waking hours. Consciously or unconsciously, the bilingual brain constantly has to decide: Shall I think, speak, or interpret sounds spoken to me according to the arbitrary rules of language A or language B? There are other unanswered questions. If one extra language offers some protection, do two extra languages offer more protection? If so, is the relationship between protection and number of extra languages linear, sublinear, or supralinear? For example, if bilinguals get 5 years of protection from their one

extra language, do Scandinavian shop assistants speaking five languages also get just 5 years of protection, or do they get 5 × 4 = 20 years of protection? If you, alas, were not raised as a crib bilingual, will learning a second language in school let you catch up? Do bilinguals’ advantages in coping with rule changes and confusing cues extend beyond trivial game tasks to real-life situations, such as school success and understanding other peoples’ mental states? What neural mechanisms underlie bilingualism’s reported protection against Alzheimer’s symptoms? These questions will be of theoretical interest to linguists, and of practical interest to parents wondering how best to raise their children.

Downloaded from www.sciencemag.org on November 26, 2010

the left side of a computer screen. The infants were conditioned to anticipate the puppet by first hearing a nonsense trisyllable (e.g., “lo-lo-vu”). Within nine trials, both monolingual and bilingual infants learned to look toward the screen’s left side when they heard that trisyllable. But when Kovács and Mehler changed the rules and made the puppet appear on the screen’s right side after broadcasting a different trisyllable, the “bilingual” infants unlearned their previous lesson and learned the new response within six more trials. In contrast, the “monolingual” infants couldn’t learn the new response even after nine trials. Evidently, shifting frequently and unpredictably between hearing two parental languages made “bilingual” infants better able to cope with other unpredictable rule changes. Do these findings suggest that bilinguals have an advantage over monolinguals in negotiating our confusing world of changing rules, and not merely in the task of discriminating lo-lo-vu from lo-vu-lo? You readers may demand evidence of more tangible benefits before you commit yourselves to babbling in two different languages to your infant children. Hence, you may be more impressed by recent results suggesting a protective effect of lifelong bilingualism against symptoms of Alzheimer’s disease (10). Among hundreds of elderly Canadian patients with a probable Alzheimer’s diagnosis, bilingual patients

References

1. E. Bialystok, Dev. Psychol. 46, 93 (2010). 2. E. Bialystok, X. Feng, Brain Lang. 109, 93 (2009). 3. E. Bialystok, M. Viswanathan, Cognition 112, 494 (2009). 4. A. M. Kovács, J. Mehler, Science 325, 611 (2009). 5. A. M. Kovács, J. Mehler, Proc. Natl. Acad. Sci. U.S.A. 106, 6556 (2009). 6. E. Bialystok, Bilingualism and Development (Cambridge Univ. Press, New York, 2001). 7. S. M. Carlson, A. N. Meltzoff, Dev. Sci. 11, 282 (2008). 8. A. Costa, M. Hernández, N. Sebastián-Gallés, Cognition 106, 59 (2008). 9. T. Shallice, From Neuropsychology to Mental Structure (Cambridge Univ. Press, Cambridge, 1988) 10. E. Bialystok, F. I. Craik, M. Freedman, Neuropsychologia 45, 459 (2007). 10.1126/science.1195067

MATERIALS SCIENCE

Recasting Metal Alloy Phases with Block Copolymers

Highly complex metal alloy phases have been replicated at a larger scale with spherical aggregates formed from polymers.

Mihai Peterca and Virgil Percec*

C

rystalline order develops through a balance between short-range attractive and repulsive interactions (1) that not only operate on atoms but work at the nanoscale on supramolecular structures (2). Spherical particles often pack together into simple, high-symmetry arrangements, but more complex topologically closepacked structures, such as the Frank-Kasper σ phase (3, 4) first seen in metal alloys, have also been observed (see the figure, panel A). Spherical supramolecular aggregates formed Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104– 6323, USA. *To whom correspondence should be addressed. E-mail: [email protected]

from polymers and monodisperse branched macromolecules (5–7) can be used to mimic atoms and explore how these phases arise. On page 349 of this issue, Lee et al. (8) show that linear block copolymers that form spherical aggregates through microphase separation can crystallize into a FrankKasper σ phase. Relative to metal alloys, the volume of its crystalline repeating unit, the unit cell, is six orders of magnitude greater (see the figure, panel C). The scaling up of atomic lattices by using spherical supramolecular aggregates is also of practical interest because such structures could be used as photonic materials (9), nanoreactors (5), or drug delivery vehicles (10). Understanding how spherical supramo-

lecular aggregates organize into crystals remains a challenging task. In the ideal case of incompressible “hard” spheres—which are a good model for metal atoms—the most stable structures correspond to the hexagonal close-packed (hcp) and face-centered cubic (fcc) periodic close-packing configurations shown in panel A of the figure. These structures maximize the packing of atoms and fill 74% of their unit cell volume (versus 68% for the body-centered cubic, or bcc, packing). The stability of the packing derives from large numbers of nearest neighbors interactions that decrease free energy. Spherical aggregates formed by soft macromolecules, including block copolymers, should follow the same principle and pre-

www.sciencemag.org SCIENCE VOL 330 15 OCTOBER 2010 Published by AAAS

333