Threshold Hypothesis

The threshold hypothesis is a hypothesis about the cognitive effects of bilingualism, put forward by the researcher Jim Cummins in a study published in 1976. It proposes that a bilingual child must reach a minimum, or threshold, level of competence in both of their languages before the fact of being bilingual can produce positive cognitive effects, and that a child who has not reached that threshold level in either language, sometimes described as a case of limited or subtractive bilingualism, may instead experience negative cognitive consequences rather than benefiting from knowing two languages. Cummins proposed the idea partly to reconcile conflicting findings in earlier research, some of which had found bilingual children to be cognitively disadvantaged relative to monolingual children and some of which had found the opposite, suggesting that the level of proficiency actually reached in each language, rather than bilingualism itself, was the factor determining whether the outcome was positive or negative. The threshold hypothesis has been particularly influential in debates over bilingual education policy, since it implies that a program allowed to leave children only partially proficient in either language risks the negative outcomes the hypothesis describes, while a program that builds strong proficiency in both languages is positioned to produce the positive cognitive effects associated with genuine bilingualism.