Numerous research studies in the past 30 years have concluded that fluent bilingualism contributes to the cognitive growth of children. Most of this research has focused on the outcomes of bilingualism, however, so the exact processes through which bilingualism and cognition interact are still largely unknown (Hakuta, Ferdman, & Diaz, 1986). Nonetheless, most researchers believe that knowing two languages and perspectives gives bilingual children a more diversified and flexible basis for cognition than their monolingual peers have.
Cataldi (1994) believes that learning two languages well "gives rise to mental flexibility, a superiority in concept formation, and a more diversified set of mental abilities" (p. 63). Diaz (1985) argues that strong knowledge of two languages enhances a child's "metalinguistic awareness." This awareness can serve as a critical component in the development of intelligence. He further notes that bilingual-bicultural children can experience the world from two perspectives, allowing them to mature more quickly than their monolingual peers.
Shedding New Light on Bilingualism
Bilingualism has not always been seen in such a positive light, however. In the first half of the 20th century, most studies concluded that bilingual students performed less well than monolingual students on IQ tests and other cognitive measures (Diaz, 1985). A 1962 study of Canadian bilingual students by Peal and Lambert, however, is widely credited with causing researchers to reexamine these earlier findings. After controlling for variables like socioeconomic status, Peal and Lambert found that the true bilingual students outperformed their mono-lingual peers on several verbal and nonverbal tests of intelligence. Subsequent research has largely supported this conclusion (Hakuta, 1985).
One reason that more recent research has tended to debunk the negative findings of earlier studies is that bilingual children are no longer lumped in a single category that does not account for their relative fluency levels. For example, Peal and Lambert (1962) differentiated between "balanced" bilingual children, who communicate equivalently well in two languages, and pseudo-bilinguals, who are clearly more facile in one language than in the other and who use that one language almost exclusively in communicating.
Döpke, McNamara, and Quinn (1991) and others have used the terms additive and subtractive bilinguals. Additive bilingual programs develop first and second language proficiency fully, whereas subtractive programs halt first language development. Whatever the terminology used, language abilities vary greatly, and this variance appears to affect how children's bilingualism interacts with their cognitive development. Indeed, Diaz (1985) summarized relevant research by noting that "cognitive and academic advantages observed in bilingual children are usually the result of 'additive' rather than subtractive' programs" (p. 77).
Similarly, in her case study of nine bilingual Italian children, D'Acierno (1990) described one boy caught between his English-speaking mother and his Italian relatives who worried about possible negative effects of his bilingualism. In this situation, in which the boy was forced to choose one language over the other, D'Acierno found that the boy's cognitive and even motor development suffered. Within the families who encouraged and embraced bilingualism, D'Acierno found that the bilingualism positively influenced cognitive development.
Language Proficiency and Other Factors
A 1995 study by Saito-Horgan supports this view that bilingualism does not automatically enhance cognitive development regardless of language fluency and relevant social factors. Saito-Horgan studied four groups of bilingual Hispanic children to determine their stages of development. The children engaged in three Piagetian tasks involving classification, conservation of mass, and conservation of area. None of the four groups was found to possess a cognitive advantage over monolingual students on the three tasks.
Does this mean that bilingualism is unrelated to cognitive development? Probably not. As Saito-Horgan notes, all the children came from subtractive bilingual programs, which may have mitigated any potentially positive impact the children's bilingualism might have had on cognitive development. Moreover, all the children came from less advantaged socioeconomic backgrounds. Hakuta, Ferdman, and Diaz (1986) note that bilingual studies that group children by a societal definition of bilingualism—such as all Hispanic children from lower socioeconomic backgrounds—as opposed to a cognitive definition—based on level of language proficiency—fail to disentangle the impacts of the children's social background from the impacts of their bilingualism.
Even the general consensus that additive or balanced bilingualism enhances cognition is not universally accepted. For example, Williams and Snipper (1990) argue that it is "misconceived" to think of the relationship as causal. They believe that at best the research shows bilingualism and cognition exerting a minimal, reciprocal influence on each other.
Hakuta, Ferdman, and Diaz (1986) criticize studies that make "gross inferences regarding causality" and use cautious language in analyzing their own data. They argue that "if bilingualism and intelligence are causally related, bilingualism is most likely the causal factor" (p. 20). They recognize that the exact nature of this interaction is still more a matter of hypothesis than certainty.
Thus, to propose that bilingualism automatically enhances cognitive development is too strong a statement. In fact, some would argue that children who are not developing full proficiency in both languages may actually find their bilingualism a hindrance. Even Hakuta (1985), whose work generally supports a positive connection between bilingualism and cognitive development, cautions that bilingualism should not be used as an intervention to increase children's cognitive performance.
In the right circumstances, however, fluent bilingualism can play a positive role. D'Acierno's 1990 case study suggests that if bilingualism is celebrated by children's families (and, by extension, their school communities), it can have a positive developmental influence. Diaz (1985) concurs, arguing not only that children have a legal right to bilingual education, but also that bilingual education provides an "excellent tool" that can help students of all language backgrounds fulfill their academic and intellectual potential.
