The present study investigated the development of verbal and spatial abilities over time within a group of Spanish(L1)-English(L2) bilingual children currently attending Kindergarten and First-grade bilingual education programs. The study was designed in response to methodological gaps in current research on bilinguals' cognitive development; in particular, the study examined the cognitive effects of bilingualism on children who are just beginning to learn a second language and proposed a measure of degree of bilingualism that effectively controls for basic ability in the dominant language. The results firmly supported the claim that bilingualism fosters the development of verbal and spatial abilities. The relationship between degree of bilingualism and cognitive abilities was particularly strong for children of low second-language proficiency. This pattern of results questioned the validity of Cummins' threshold hypothesis and suggested a new, alternative threshold hypothesis. The new (Diaz) threshold hypothesis states that variability in second-language proficiency would be related to variability in cognitive measures only before a certain threshold of proficiency in the second language is attained. Two different sets of statistical analyses gave support to a cause-effect model where degree of bilingualism is the causal factor affecting cognitive abilities. An experimental study examined the construct of cognitive flexibility and provided some support for the claim that the nonverbal advantages observed in bilingual children could be explained by their use of verbal mediation in the processing of nonverbal tasks.
THE IMPACT OF SECOND-LANGUAGE LEARNING ON THE DEVELOPMENT OF VERBAL AND SPATIAL ABILITIES. (PhD, Yale University ).
DIAZ, R. M. (1982).