Mitsunori Takakuwa (*)
What is cognitive development in the studies of bilingualism? The belief widely held up to the 1960s that bilingualism had only negative effects on children's cognitive development, as measured by I.Q. has been challenged. It is now believed that bilingualism has a positive effect on children's cognitive development (e.g., Bialystok 1938; Day and Shapson 1996; Palij and Homel 1987). However, the area to which the term cognitive development refers is broad and vague. An examination of the literature suggests that the study of bilingualism has only shown that bilingualism may have a positive effect on children's metalinguistic awareness, which is a kind of cognitive development. This paper examines critically what is meant by cognitive development in the studies of bilingualism, and points out methodological problems and limitations of findings by some often-cited studies in the literature.
From the nineteenth century to the 1960s, bilingualism was regarded as having a harmful effect on cognitive development (Ausubel, Sullivan, and Ives 1980; Darcy 1953). Bilingualism was said to hamper children's development of intelligence and to lead children to psychological confusion (Laurie 1890; Saer 1923; Smith 1923). The findings of such studies opposed bilingualism by showing that bilingual children scored lower on measures of verbal intelligence than monolingual children, although there was no difference between the two groups on measures of nonverbal intelligence.
Peal and Lambert's (1962) study is often considered to be a turning point in how bilingualism is viewed in the sense that, after their study, bilingualism became recognized as having a cognitive advantage (Palij and Homel 1987). By studying ten-year-olds from French schools in Montreal, Canada, Peal and Lambert (1962) found that the bilingual group scored higher than the monolingual group on 15 out of 18 measures of intelligence, whereas there was no difference between the two groups on the other 3 measures. The bilingual group scored higher than the monolingual group on measures of both verbal and nonverbal intelligence. This finding contradicted the results of previous research that bilingual children were considered to be cognitively inferior to monolingual children. More recent research on bilingualism has shown that there is an opposing view that bilingualism has a positive effect on children's cognitive development (Bialystok 1988; Day and Shapson 1996; Palij and Home, 1987).
The former view has not held up since these early studies failed to implement adequate methodological controls, whereas the latter view appears generally supported because the study by Peal and Lambert (1962) and subsequent studies attempted to use controlled, experimental research designs (Bialystok 1988; Palij and Homel 1987). However, this latter view cannot go without criticism. First of all, adequate methodological controls have only served to ensure that the bilinguals and the monolinguals to be used as the control group are matched on such variables as socioeconomic status, sex, and age. However, selection according these criteria does not guarantee that the variables of children's families and other background factors such as student motivation and parental attitude are controlled (Carey 1991; Diaz 1985). Whether or not a study uses such methodological controls, the methodology using the comparison between the bilinguals and the monolinguals itself is problematic (Carey 1991; Diaz 1985; Reynolds 1991 ). Second, whether advantageous or disadvantageous, the alleged cognitive consequences of bilingualism have been generally studied by referring to its impact on "intelligence," usually measured by I.Q However, intelligence itself is "a controversial concept" (Romaine 1995, 107). How intelligence can be defined and measured is still a disputable point (Baker 1993). Third, apart from intelligence, what is meant by cognitive development varies from study to study. …