Studies conducted with middle-class balanced bilinguals in "additive" environments, where both languages are prestigious, have generally reported that bilinguals showed a higher level of cognitive performance than monolinguals. In these studies, bilinguals showed higher levels of general intellectual skills, higher levels of divergent thinking, a more analytic orientation to language and greater sensitivity to feedback cues. However, studies conducted in "subtractive" environments, where the less prestigious first language is in the process of replacement by the second language, have tended to report that bilinguals experienced difficulties in expressing their intelligence through language. The competence that a bilingual gains in his two languages may act as an intervening variable in mediating the effects of his bilingual learning experiences on cognitive growth, i.e., there may be threshold levels of linguistic competence which bilingual children must attain in order both to avoid cognitive deficits and to allow the potentially beneficial aspects of becoming bilingual to influence cognitive growth. (Author/CFM)